XPath and XQuery Functions and Operators 4.0

1 Introduction

The purpose of this document is to define functions and operators for inclusion in XPath 4.0, XQuery 4.0, and XSLT 4.0. The exact syntax used to call these functions and operators is specified in [XML Path Language (XPath) 4.0], [XQuery 4.1: An XML Query Language] and [XSL Transformations (XSLT) Version 4.0].

This document defines three classes of functions:

General purpose functions, available for direct use in user-written queries, stylesheets, and XPath expressions, whose arguments and results are values defined by the [XQuery and XPath Data Model (XDM) 3.1].
Constructor functions, used for creating instances of a datatype from values of (in general) a different datatype. These functions are also available for general use; they are named after the datatype that they return, and they always take a single argument.
Functions that specify the semantics of operators defined in [XML Path Language (XPath) 4.0] and [XQuery 4.1: An XML Query Language]. These exist for specification purposes only, and are not intended for direct calling from user-written code.

[XML Schema Part 2: Datatypes Second Edition] defines a number of primitive and derived datatypes, collectively known as built-in datatypes. This document defines functions and operations on these datatypes as well as the other types (for example, nodes and sequences of nodes) defined in Section 2.7 Schema Information ^DM31 of the [XQuery and XPath Data Model (XDM) 3.1]. These functions and operations are available for use in [XML Path Language (XPath) 4.0], [XQuery 4.1: An XML Query Language] and any other host language that chooses to reference them. In particular, they may be referenced in future versions of XSLT and related XML standards.

[Schema 1.1 Part 2] adds to the datatypes defined in [XML Schema Part 2: Datatypes Second Edition]. It introduces a new derived type xs:dateTimeStamp, and it incorporates as built-in types the two types xs:yearMonthDuration and xs:dayTimeDuration which were previously XDM additions to the type system. In addition, XSD 1.1 clarifies and updates many aspects of the definitions of the existing datatypes: for example, it extends the value space of xs:double to allow both positive and negative zero, and extends the lexical space to allow +INF; it modifies the value space of xs:Name to permit additional Unicode characters; it allows year zero and disallows leap seconds in xs:dateTime values; and it allows any character string to appear as the value of an xs:anyURI item. Implementations of this specification may support either XSD 1.0 or XSD 1.1 or both.

References to specific sections of some of the above documents are indicated by cross-document links in this document. Each such link consists of a pointer to a specific section followed a superscript specifying the linked document. The superscripts have the following meanings: XQ [XQuery 4.1: An XML Query Language], XT [XSL Transformations (XSLT) Version 4.0], XP [XML Path Language (XPath) 4.0], and DM [XQuery and XPath Data Model (XDM) 3.1].

1.1 Operators

Despite its title, this document does not attempt to define the semantics of all the operators available in the [XML Path Language (XPath) 4.0] language; indeed, in the interests of avoiding duplication, the majority of operators (including all higher-order operators such as x/y, x!y, and x[y], as well simple operators such as x,y, x and y, x or y, x<<y, x>>y, x is y, x||y, x|y, x union y, x except y, x intersect y, x to y and x otherwise y) are now defined entirely within [XML Path Language (XPath) 4.0].

The remaining operators that are described in this publication are those where the semantics of the operator depend on the types of the arguments. For these operators, the language specification describes rules for selecting an internal function defined in this specification to underpin the operator. For example, when the operator x+y is applied to two operands of type xs:double, the function op:numeric-add is selected.

XPath defines a range of comparison operators x=y, x!=y, x<y, x>y, x<=y, x>=y, x eq y, x ne y, x lt y, x gt y, x le y, x ge y, which apply to a variety of operand types including for example numeric values, strings, dates and times, and durations. For each relevant data type, two functions are defined in this specification, for example op:date-equal and op:date-less-than. These define the semantics of the eq and lt operators applied to operands of that data type. The operators x ne y, x gt y, x le y, and x ge y are defined by reference to these two; and the general comparison operators =, !=, <, >, <=, and >= are defined by reference to eq, ne, lt, gt, le, and ge respectively.

Note:

Previous versions of this specification also defined a third comparison function of the form op:date-greater-than. This has been dropped, as it is always the inverse of the -less-than form.

1.2 Conformance

This recommendation contains a set of function specifications. It defines conformance at the level of individual functions. An implementation of a function conforms to a function specification in this recommendation if all the following conditions are satisfied:

For all combinations of valid inputs to the function (both explicit arguments and implicit context dependencies), the result of the function meets the mandatory requirements of this specification.
For all invalid inputs to the function, the implementation raises (in some way appropriate to the calling environment) a dynamic error.
For a sequence of calls within the same ·execution scope·, the requirements of this recommendation regarding the ·determinism· of results are satisfied (see 1.8.4 Properties of functions).

Other recommendations (“host languages”) that reference this document may dictate:

Subsets or supersets of this set of functions to be available in particular environments;
Mechanisms for invoking functions, supplying arguments, initializing the static and dynamic context, receiving results, and handling errors;
A concrete realization of concepts such as ·execution scope·;
Which versions of other specifications referenced herein (for example, XML, XSD, or Unicode) are to be used.

Any behavior that is discretionary (implementation-defined or implementation-dependent) in this specification may be constrained by a host language.

Note:

Adding such constraints in a host language, however, is discouraged because it makes it difficult to reuse implementations of the function library across host languages.

This specification allows flexibility in the choice of versions of specifications on which it depends:

It is ·implementation-defined· which version of Unicode is supported, but it is recommended that the most recent version of Unicode be used.
It is ·implementation-defined· whether the type system is based on XML Schema 1.0 or XML Schema 1.1.
It is ·implementation-defined· whether definitions that rely on XML (for example, the set of valid XML characters) should use the definitions in XML 1.0 or XML 1.1.

Note:

The XML Schema 1.1 recommendation introduces one new concrete datatype: xs:dateTimeStamp; it also incorporates the types xs:dayTimeDuration, xs:yearMonthDuration, and xs:anyAtomicType which were previously defined in earlier versions of [XQuery and XPath Data Model (XDM) 3.1]. Furthermore, XSD 1.1 includes the option of supporting revised definitions of types such as xs:NCName based on the rules in XML 1.1 rather than 1.0.

The [XQuery and XPath Data Model (XDM) 4.0] allows flexibility in the repertoire of characters permitted during processing that goes beyond even what version of XML is supported. A processor may allow the user to construct nodes and atomic values that contain characters not allowed by any version of XML. [Definition] A permitted character is one within the repertoire accepted by the implementation.

In this document, text labeled as an example or as a note is provided for explanatory purposes and is not normative.

1.3 Namespaces and prefixes

The functions and operators defined in this document are contained in one of several namespaces (see [Namespaces in XML]) and referenced using an xs:QName.

This document uses conventional prefixes to refer to these namespaces. User-written applications can choose a different prefix to refer to the namespace, so long as it is bound to the correct URI. The host language may also define a default namespace for function calls, in which case function names in that namespace need not be prefixed at all. In many cases the default namespace will be http://www.w3.org/2005/xpath-functions, allowing a call on the fn:name function (for example) to be written as name() rather than fn:name(); in this document, however, all example function calls are explicitly prefixed.

The URIs of the namespaces and the conventional prefixes associated with them are:

http://www.w3.org/2001/XMLSchema for constructors — associated with xs.

The section 20 Constructor functions defines constructor functions for the built-in datatypes defined in [XML Schema Part 2: Datatypes Second Edition] and in Section 2.7 Schema Information ^DM31 of [XQuery and XPath Data Model (XDM) 3.1]. These datatypes and the corresponding constructor functions are in the XML Schema namespace, http://www.w3.org/2001/XMLSchema, and are named in this document using the xs prefix.
http://www.w3.org/2005/xpath-functions for functions — associated with fn.

The namespace prefix used in this document for most functions that are available to users is fn.
http://www.w3.org/2005/xpath-functions/math for functions — associated with math.

This namespace is used for some mathematical functions. The namespace prefix used in this document for these functions is math. These functions are available to users in exactly the same way as those in the fn namespace.
http://www.w3.org/2005/xpath-functions/map for functions — associated with map.

This namespace is used for some functions that manipulate maps (see 18.2 Functions that Operate on Maps). The namespace prefix used in this document for these functions is map. These functions are available to users in exactly the same way as those in the fn namespace.
http://www.w3.org/2005/xpath-functions/array for functions — associated with array.

This namespace is used for some functions that manipulate maps (see 19.1 Functions that Operate on Arrays). The namespace prefix used in this document for these functions is array. These functions are available to users in exactly the same way as those in the fn namespace.
http://www.w3.org/2005/xqt-errors — associated with err.

There are no functions in this namespace; it is used for error codes.

This document uses the prefix err to represent the namespace URI http://www.w3.org/2005/xqt-errors, which is the namespace for all XPath and XQuery error codes and messages. This namespace prefix is not predeclared and its use in this document is not normative.
http://www.w3.org/2010/xslt-xquery-serialization — associated with output.

There are no functions in this namespace: it is used for serialization parameters, as described in [XSLT and XQuery Serialization 3.1]

Functions defined with the op prefix are described here to underpin the definitions of the operators in [XML Path Language (XPath) 4.0], [XQuery 4.1: An XML Query Language] and [XSL Transformations (XSLT) Version 4.0]. These functions are not available directly to users, and there is no requirement that implementations should actually provide these functions. For this reason, no namespace is associated with the op prefix. For example, multiplication is generally associated with the * operator, but it is described as a function in this document:

`op:numeric-multiply`(
`$arg1`	`as` `xs:numeric`,
`$arg2`	`as` `xs:numeric`
) `as` `xs:numeric`

Sometimes there is a need to use an operator as a function. To meet this requirement, the function fn:op takes any simple binary operator as its argument, and returns a corresponding function. So for example fn:for-each-pair($seq1, $seq2, op("+")) performs a pairwise addition of the values in two input sequences.

Note:

The above namespace URIs are not expected to change from one version of this document to another. The contents of these namespaces may be extended to allow additional functions (and errors, and serialization parameters) to be defined.

1.4 Function overloading

A function is uniquely defined by its name and arity (number of arguments); it is therefore not possible to have two different functions that have the same name and arity, but different types in their signature. That is, function overloading in this sense of the term is not permitted. Consequently, functions such as fn:string which accept arguments of many different types have a signature that defines a very general argument type, in this case item()? which accepts any single item; supplying an inappropriate item (such as a function item) causes a dynamic error.

Some functions on numeric types include the type xs:numeric in their signature as an argument or result type. In this version of the specification, xs:numeric has been redefined as a built-in union type representing the union of xs:decimal, xs:float, xs:double (and thus automatically accepting types derived from these, including xs:integer).

Operators such as + may be overloaded: they map to different underlying functions depending on the dynamic types of the supplied operands.

It is possible for two functions to have the same name provided they have different arity (number of arguments). For the functions defined in this specification, where two functions have the same name and different arity, they also have closely related behavior, so they are defined in the same section of this document.

1.5 Function signatures and descriptions

Each function (or group of functions having the same name) is defined in this specification using a standard proforma.

The function name is a QName as defined in [XML Schema Part 2: Datatypes Second Edition] and must adhere to its syntactic conventions. Following the precedent set by [XML Path Language (XPath) Version 1.0], function names are generally composed of English words separated by hyphens (-). Abbreviations are used only where there is a strong precedent in other programming languages (as with math:sin and math:cos for sine and cosine). If a function name contains a [XML Schema Part 2: Datatypes Second Edition] datatype name, it may have intercapitalized spelling and is used in the function name as such. An example is fn:timezone-from-dateTime.

The first section in the proforma is a short summary of what the function does. This is intended to be informative rather than normative.

Each function is then defined by specifying its signature(s), which define the types of the parameters and of the result value.

Where functions take a variable number of arguments, two conventions are used:

Wherever possible, a single function signature is used giving default values for those parameters that can be omitted.
If this is not possible, because the effect of omitting a parameter cannot be specified by giving a default value, multiple signatures are given for the function.

Each function signature is presented in a form like this:

`fn:function-name`(
`$parameter-name`	`as` `parameter-type`,
`$...`	`as`
) `as` `return-type`

In this notation, function-name, in bold-face, is the local name of the function whose signature is being specified. The prefix fn indicates that the function is in the namespace http://www.w3.org/2005/xpath-functions: this is one of the conventional prefixes listed in 1.3 Namespaces and prefixes. If the function takes no parameters, then the name is followed by an empty parameter list: (); otherwise, the name is followed by a parenthesized list of parameter declarations. Each parameter declaration includes:

The name of the parameter (which in 4.0 is significant because it can be used as a keyword in a function call)
The static type of the parameter (in italics)
If the parameter is optional, then an expression giving the default value (preceded by the symbol :=).

The default value expression is evaluated using the static and dynamic context of the function caller (or of a named function reference). For example, if the default value is given as ., then it evaluates to the context value from the dynamic context of the function caller; if it is given as default-collation, then its value is the default collation from the static context of the function caller; if it is given as deep-equal#2, then the third argument supplied to deep-equal is the default collation from the static context of the caller.

If there are two or more parameter declarations, they are separated by a comma.

The return-type, also in italics, specifies the static type of the value returned by the function. The dynamic type of the value returned by the function is the same as its static type or derived from the static type. All parameter types and return types are specified using the SequenceType notation defined in Section 2.5.4 SequenceType Syntax ^XP31.

One function, fn:concat, has a variable number of arguments (zero or more). More strictly, there is an infinite set of functions having the name fn:concat, with arity ranging from 0 to infinity. For this special case, a single function signature is given, with an ellipsis indicating an indefinite number of arguments.

The next section in the proforma defines the semantics of the function as a set of rules. The order in which the rules appear is significant; they are to be applied in the order in which they are written. Error conditions, however, are generally listed in a separate section that follows the main rules, and take precedence over non-error rules except where otherwise stated. The principles outlined in Section 2.3.4 Errors and Optimization ^XP31 apply by default: to paraphrase, if the result of the function can be determined without evaluating all its arguments, then it is not necessary to evaluate the remaining arguments merely in order to determine whether any error conditions apply.

Where the proforma includes sections headed Notes or Examples, these are non-normative.

Rules for passing parameters to operators are described in the relevant sections of [XQuery 4.1: An XML Query Language] and [XML Path Language (XPath) 4.0]. For example, the rules for passing parameters to arithmetic operators are described in Section 3.5 Arithmetic Expressions ^XP31. Specifically, rules for parameters of type xs:untypedAtomic and the empty sequence are specified in this section.

As is customary, the parameter type name indicates that the function or operator accepts arguments of that type, or types derived from it, in that position. This is called subtype substitution (See Section 2.5.5 SequenceType Matching ^XP31). In addition, numeric type instances and instances of type xs:anyURI can be promoted to produce an argument of the required type. (See Section B.1 Type Promotion ^XP31).

Subtype Substitution: A derived type may substitute for its base type. In particular, xs:integer may be used where xs:decimal is expected.
Numeric Type Promotion: xs:decimal may be promoted to xs:float or xs:double. Promotion to xs:double should be done directly, not via xs:float, to avoid loss of precision.
anyURI Type Promotion: A value of type xs:anyURI can be promoted to the type xs:string.

Some functions accept a single value or the empty sequence as an argument and some may return a single value or the empty sequence. This is indicated in the function signature by following the parameter or return type name with a question mark: ?, indicating that either a single value or the empty sequence must appear. See below.

`fn:function-name`(
`$parameter-name`	`as` `parameter-type`
) `as` `return-type?`

Note that this function signature is different from a signature in which the parameter is omitted. See, for example, the two signatures for fn:string. In the first signature, the parameter is omitted and the argument defaults to the context value, referred to as .. In the second signature, the argument must be present but may be the empty sequence, written as ().

Some functions accept a sequence of zero or more values as an argument. This is indicated by following the name of the type of the items in the sequence with *. The sequence may contain zero or more items of the named type. For example, the function below accepts a sequence of xs:double and returns a xs:double or the empty sequence.

`fn:median`(
`$arg`	`as` `xs:double*`
) `as` `xs:double?`

In XPath 4.0, the arguments in a function call can be supplied by keyword as an alternative to supplying them positionally. For example the call resolve-uri(@href, static-base-uri()) can now be written resolve-uri(base: static-base-uri(), relative: @href). The order in which arguments are supplied can therefore differ from the order in which they are declared. The specification, however, continues to use phrases such as “the second argument” as a convenient shorthand for "the value of the argument that is bound to the second parameter declaration".

1.6 Options

As a matter of convention, a number of functions defined in this document take a parameter whose value is a map, defining options controlling the detail of how the function is evaluated. Maps are a new datatype introduced in XPath 3.1.

For example, the function fn:xml-to-json has an options parameter allowing specification of whether the output is to be indented. A call might be written:

xml-to-json($input, map{'indent':true()})

[Definition] Functions that take an options parameter adopt common conventions on how the options are used. These are referred to as the option parameter conventions. These rules apply only to functions that explicitly refer to them.

Where a function adopts the ·option parameter conventions·, the following rules apply:

The value of the relevant argument must be a map. The entries in the map are referred to as options: the key of the entry is called the option name, and the associated value is the option value. Option names defined in this specification are always strings (single xs:string values). Option values may be of any type.
The type of the options parameter in the function signature is always given as map(*).
Although option names are described above as strings, the actual key may be any value that compares equal to the required string (using the eq operator with Unicode codepoint collation; or equivalently, the fn:atomic-equal relation). For example, instances of xs:untypedAtomic or xs:anyURI are equally acceptable.

Note:

This means that the implementation of the function can check for the presence and value of particular options using the functions map:contains and/or map:get.
It is not an error if the options map contains options with names other than those described in this specification. Implementations may attach an ·implementation-defined· meaning to such entries, and may define errors that arise if such entries are present with invalid values. Implementations must ignore such entries unless they have a specific ·implementation-defined· meaning. Implementations that define additional options in this way should use values of type xs:QName as the option names, using an appropriate namespace.
All entries in the options map are optional, and supplying an empty map has the same effect as omitting the relevant argument in the function call, assuming this is permitted.
For each named option, the function specification defines a required type for the option value. The value that is actually supplied in the map is converted to this required type using the function conversion rules^XP31. This will result in an error (typically [err:XPTY0004]^XP or [err:FORG0001]^FO) if conversion of the supplied value to the required type is not possible. A type error also occurs if this conversion delivers a coerced function whose invocation fails with a type error. A dynamic error occurs if the supplied value after conversion is not one of the permitted values for the option in question: the error codes for this error are defined in the specification of each function.

Note:

It is the responsibility of each function implementation to invoke this conversion; it does not happen automatically as a consequence of the function-calling rules.
In cases where an option is list-valued, by convention the value may be supplied either as a sequence or as an array. Accepting a sequence is convenient if the value is generated programmatically using an XPath expression; while accepting an array allows the options to be held in an external file in JSON format, to be read using a call on the fn:json-doc function.
In cases where the value of an option is itself a map, the specification of the particular function must indicate whether or not these rules apply recursively to the contents of that map.

1.7 Type System

The diagrams in this section show how nodes, functions, primitive simple types, and user defined types fit together into a type system. This type system comprises two distinct subsystems that both include the primitive atomic types. In the diagrams, connecting lines represent relationships between derived types and the types from which they are derived; the former are always below and to the right of the latter.

The xs:IDREFS, xs:NMTOKENS, xs:ENTITIES types, and xs:numeric and both the user-defined list types and user-defined union types are special types in that these types are lists or unions rather than types derived by extension or restriction.

1.7.1 Item Types

The first diagram illustrates the relationship of various item types.

Item types are used to characterize the various types of item that can appear in a sequence (nodes, atomic values, and functions), and they are therefore used in declaring the types of variables or the argument types and result types of functions.

Item types in the data model form a directed graph, rather than a hierarchy or lattice: in the relationship defined by the derived-from(A, B) function, some types are derived from more than one other type. Examples include functions (function(xs:string) as xs:int is substitutable for function(xs:NCName) as xs:int and also for function(xs:string) as xs:decimal), and union types (A is substitutable for union(A, B) and also for union(A, C). In XDM, item types include node types, function types, and built-in atomic types. The diagram, which shows only hierarchic relationships, is therefore a simplification of the full model.

item (abstract)
- anyAtomicType (built-in atomic)
- node (node)
  - attribute (node)
    - user-defined attribute types (user-defined)
  - document (node)
    - user-defined document types (user-defined)
  - element (node)
    - user-defined element types (user-defined)
  - text (node)
  - comment (node)
  - processing-instruction (node)
  - namespace (node)
- function(*) (function item)
  - array(*) (function item)
  - map(*) (function item)

Legend:

Supertype
- subtype

Abstract types (abstract)
Built-in atomic types (built-in atomic)
Node types (node)
Function item types (function item)
User-defined types (user-defined)

1.7.2 Schema Type Hierarchy

The next diagram illustrate the schema type subsystem, in which all types are derived from xs:anyType.

Schema types include built-in types defined in the XML Schema specification, and user-defined types defined using mechanisms described in the XML Schema specification. Schema types define the permitted contents of nodes. The main categories are complex types, which define the permitted content of elements, and simple types, which can be used to constrain the values of both elements and attributes.

XML Schema types (abstract)
- anyType (built-in complex)
  - Simple types (abstract)
    - anySimpleType (built-inlist)
      - Atomic types (abstract)
        
        anyAtomicType (built-in atomic)
      - list types (abstract)
        
        ENTITIES (built-in list)
        
        IDREFS (built-in list)
        
        NMTOKENS (built-in list)
        
        user-defined list types (user-defined)
      - union types (abstract)
        
        numeric (built-in complex)
        
        user-defined union types (user-defined)
    - complex types (complex)
      - untyped (built-in complex)
      - user-defined complex types (user-defined)

Legend:

Supertype
- subtype

Abstract types (abstract)
Built-in atomic types (built-in atomic)
Built-in complex types (built-in complex)
Built-in list types (built-in list)
User-defined types (user-defined)

1.7.3 Atomic Type Hierarchy

The final diagram shows all of the atomic types, including the primitive simple types and the built-in types derived from the primitive simple types. This includes all the built-in datatypes defined in [XML Schema Part 2: Datatypes Second Edition].

Atomic types are both item types and schema types, so the root type xs:anyAtomicType may be found in both the previous diagrams.

anyAtomicType
- anyURI
- base64Binary
- boolean
- date
- dateTime
  - dateTimeStamp
- decimal
  - integer
    - long
      - int
        
        short
        
        byte
    - nonNegativeInteger
      - positiveInteger
      - unsignedLong
        
        unsignedInt
        
        unsignedShort
        
        unsignedByte
    - nonPositiveInteger
      - negativeInteger
- double
- duration
  - dayTimeDuration
  - yearMonthDuration
- float
- gDay
- gMonth
- gMonthDay
- gYear
- gYearMonth
- hexBinary
- NOTATION
- QName
- string
  - normalizedString
    - token
      - NMTOKEN
      - Name
        
        NCName
        
        ENTITY
        
        ID
        
        IDREF
      - language
- time

Legend:

Supertype
- subtype

Built-in atomic types

1.8 Terminology

The terminology used to describe the functions and operators on types defined in [XML Schema Part 2: Datatypes Second Edition] is defined in the body of this specification. The terms defined in this section are used in building those definitions.

Note:

Following in the tradition of [XML Schema Part 2: Datatypes Second Edition], the terms type and datatype are used interchangeably.

1.8.1 Strings, characters, and codepoints

This document uses the terms string, character, and codepoint with meanings that are normatively defined in [XQuery and XPath Data Model (XDM) 3.1], and which are paraphrased here for ease of reference:

[Definition] A character is an instance of the Char^XML production of [Extensible Markup Language (XML) 1.0 (Fifth Edition)].

Note:

This definition excludes Unicode characters in the surrogate blocks as well as xFFFE and xFFFF, while including characters with codepoints greater than xFFFF which some programming languages treat as two characters. The valid characters are defined by their codepoints, and include some whose codepoints have not been assigned by the Unicode consortium to any character.

[Definition] A string is a sequence of zero or more ·characters·, or equivalently, a value in the value space of the xs:string datatype.

[Definition] A codepoint is an integer assigned to a ·character· by the Unicode consortium, or reserved for future assignment to a character.

Note:

The set of codepoints is thus wider than the set of characters.

This specification spells “codepoint” as one word; the Unicode specification spells it as “code point”. Equivalent terms found in other specifications are “character number” or “code position”. See [Character Model for the World Wide Web 1.0: Fundamentals]

Because these terms appear so frequently, they are hyperlinked to the definition only when there is a particular desire to draw the reader’s attention to the definition; the absence of a hyperlink does not mean that the term is being used in some other sense.

It is ·implementation-defined· which version of [The Unicode Standard] is supported, but it is recommended that the most recent version of Unicode be used.

Unless explicitly stated, the functions in this document do not ensure that any returned xs:string values are normalized in the sense of [Character Model for the World Wide Web 1.0: Fundamentals].

Note:

In functions that involve character counting such as fn:substring, fn:string-length and fn:translate, what is counted is the number of XML ·characters· in the string (or equivalently, the number of Unicode codepoints). Some implementations may represent a codepoint above xFFFF using two 16-bit values known as a surrogate pair. A surrogate pair counts as one character, not two.

1.8.2 Namespaces and URIs

This document uses the phrase “namespace URI” to identify the concept identified in [Namespaces in XML] as “namespace name”, and the phrase “local name” to identify the concept identified in [Namespaces in XML] as “local part”.

It also uses the term “expanded-QName” defined below.

[Definition] An expanded-QName is a value in the value space of the xs:QName datatype as defined in the XDM data model (see [XQuery and XPath Data Model (XDM) 3.1]): that is, a triple containing namespace prefix (optional), namespace URI (optional), and local name. Two expanded QNames are equal if the namespace URIs are the same (or both absent) and the local names are the same. The prefix plays no part in the comparison, but is used only if the expanded QName needs to be converted back to a string.

The term URI is used as follows:

[Definition] Within this specification, the term URI refers to Universal Resource Identifiers as defined in [RFC 3986] and extended in [RFC 3987] with a new name IRI. The term URI Reference, unless otherwise stated, refers to a string in the lexical space of the xs:anyURI datatype as defined in [XML Schema Part 2: Datatypes Second Edition].

Note:

This means, in practice, that where this specification requires a “URI Reference”, an IRI as defined in [RFC 3987] will be accepted, provided that other relevant specifications also permit an IRI. The term URI has been retained in preference to IRI to avoid introducing new names for concepts such as “Base URI” that are defined or referenced across the whole family of XML specifications. Note also that the definition of xs:anyURI is a wider definition than the definition in [RFC 3987]; for example it does not require non-ASCII characters to be escaped.

1.8.3 Conformance terminology

In this specification:

The auxiliary verb must, when rendered in small capitals, indicates a precondition for conformance.
- When the sentence relates to an implementation of a function (for example "All implementations must recognize URIs of the form ...") then an implementation is not conformant unless it behaves as stated.
- When the sentence relates to the result of a function (for example "The result must have the same type as $arg") then the implementation is not conformant unless it delivers a result as stated.
- When the sentence relates to the arguments to a function (for example "The value of $arg must be a valid regular expression") then the implementation is not conformant unless it enforces the condition by raising a dynamic error whenever the condition is not satisfied.
The auxiliary verb may, when rendered in small capitals, indicates optional or discretionary behavior. The statement “An implementation may do X” implies that it is implementation-dependent whether or not it does X.
The auxiliary verb should, when rendered in small capitals, indicates desirable or recommended behavior. The statement “An implementation should do X” implies that it is desirable to do X, but implementations may choose to do otherwise if this is judged appropriate.

[Definition] Where behavior is described as implementation-defined, variations between processors are permitted, but a conformant implementation must document the choices it has made.

[Definition] Where behavior is described as implementation-dependent, variations between processors are permitted, and conformant implementations are not required to document the choices they have made.

Note:

Where this specification states that something is implementation-defined or implementation-dependent, it is open to host languages to place further constraints on the behavior.

1.8.4 Properties of functions

This section is concerned with the question of whether two calls on a function, with the same arguments, may produce different results.

In this section the term function, unless otherwise specified, applies equally to function definitions^XP40 (which can be the target of a static function call) and function items^DM40 (which can be the target of a dynamic function call).

[Definition] An execution scope is a sequence of calls to the function library during which certain aspects of the state are required to remain invariant. For example, two calls to fn:current-dateTime within the same execution scope will return the same result. The execution scope is defined by the host language that invokes the function library. In XSLT, for example, any two function calls executed during the same transformation are in the same execution scope (except that static expressions, such as those used in use-when attributes, are in a separate execution scope).

The following definition explains more precisely what it means for two function calls to return the same result:

[Definition] Two values $V1 and $V2 are defined to be identical if they contain the same number of items and the items are pairwise identical. Two items are identical if and only if one of the following conditions applies:

Both items are atomic values, of precisely the same type, and the values are equal as defined using the eq operator, using the Unicode codepoint collation when comparing strings.
Both items are nodes, and represent the same node.
Both items are maps, both maps have the same number of entries, and for every entry E₁ in the first map there is an entry E₂ in the second map such that the keys of E₁ and E₂ are ·the same key·, and the corresponding values V₁ and V₂ are ·identical·.
Both items are arrays, both arrays have the same number of members, and the members are pairwise ·identical·.
Both items are function items, neither item is a map or array, and the two function items have the same function identity. The concept of function identity is explained in Section 2.9.4 Function Items^DM40.

Some functions produce results that depend not only on their explicit arguments, but also on the static and dynamic context.

[Definition] A function definition^XP40 may have the property of being context-dependent: the result of such a function depends on the values of properties in the static and dynamic evaluation context of the caller as well as on the actual supplied arguments (if any). A function definition may be context-dependent for some arities in its arity range, and context-independent for others: for example fn:name#0 is context-dependent while fn:name#1 is context-independent.

[Definition] A function definition^XP40 that is not ·context-dependent· is called context-independent.

The main categories of context-dependent functions are:

Functions that explicitly deliver the value of a component of the static or dynamic context, for example fn:static-base-uri, fn:default-collation, fn:position, or fn:last.
Functions with an optional parameter whose default value is taken from the static or dynamic context of the caller, usually either the context value (for example, fn:node-name) or the default collation (for example, fn:index-of).
Functions that use the static context of the caller to expand or disambiguate the values of supplied arguments: for example fn:doc expands its first argument using the static base URI of the caller, and xs:QName expands its first argument using the in-scope namespaces of the caller.

[Definition] A function is focus-dependent if its result depends on the focus^XP31 (that is, the context item, position, or size) of the caller.

[Definition] A function that is not ·focus-dependent· is called focus-independent.

Notes:

Note:

Some functions depend on aspects of the dynamic context that remain invariant within an ·execution scope·, such as the implicit timezone. Formally this is treated in the same way as any other context dependency, but internally, the implementation may be able to take advantage of the fact that the value is invariant.

Note:

User-defined functions in XQuery and XSLT may depend on the static context of the function definition (for example, the in-scope namespaces) and also in a limited way on the dynamic context (for example, the values of global variables). However, the only way they can depend on the static or dynamic context of the caller — which is what concerns us here — is by defining optional parameters whose default values are context-dependent.

Note:

Because the focus is a specific part of the dynamic context, all ·focus-dependent· functions are also ·context-dependent·. A ·context-dependent· function, however, may be either ·focus-dependent· or ·focus-independent·.

A function definition that is context-dependent can be used as the target of a named function reference, can be partially applied, and can be found using fn:function-lookup. The principle in such cases is that the static context used for the function evaluation is taken from the static context of the named function reference, partial function application, or the call on fn:function-lookup; and the dynamic context for the function evaluation is taken from the dynamic context of the evaluation of the named function reference, partial function application, or the call of fn:function-lookup. These constructs all deliver a function item^DM40 having a captured context based on the static and dynamic context of the construct that created the function item. This captured context forms part of the closure of the function item.

The result of a dynamic call to a function item never depends on the static or dynamic context of the dynamic function call, only (where relevant) on the the captured context held within the function item itself.

Context-dependent functions fall into a number of categories:

The functions fn:current-date, fn:current-dateTime, fn:current-time, fn:default-language, fn:implicit-timezone, fn:adjust-date-to-timezone, fn:adjust-dateTime-to-timezone, and fn:adjust-time-to-timezone depend on properties of the dynamic context that are fixed within the ·execution scope·. The same applies to a number of functions in the op: namespace that manipulate dates and times and that make use of the implicit timezone. These functions will return the same result if called repeatedly during a single ·execution scope·.
A number of functions including fn:base-uri#0, fn:data#0, fn:document-uri#0, fn:element-with-id#1, fn:id#1, fn:idref#1, fn:lang#1, fn:last#0, fn:local-name#0, fn:name#0, fn:namespace-uri#0, fn:normalize-space#0, fn:number#0, fn:path#0, fn:position#0, fn:root#0, fn:string#0, and fn:string-length#0 depend on the focus^XP31. These functions will in general return different results on different calls if the focus is different.

A function is focus-dependent if its result depends on the focus^XP31 (that is, the context value, position, or size).

A function that is not ·focus-dependent· is called focus-independent
The function fn:default-collation and many string-handling operators and functions depend on the default collation and the in-scope collations, which are both properties of the static context. If a particular call of one of these functions is evaluated twice with the same arguments then it will return the same result each time (because the static context, by definition, does not change at run time). However, two distinct calls (that is, two calls on the function appearing in different places in the source code) may produce different results even if the explicit arguments are the same.
Functions such as fn:static-base-uri, fn:doc, and fn:collection depend on other aspects of the static context. As with functions that depend on collations, a single call will produce the same results on each call if the explicit arguments are the same, but two calls appearing in different places in the source code may produce different results.

The fn:function-lookup function is a special case because it is potentially dependent on everything in the static and dynamic context. This is because the static and dynamic context of the call to fn:function-lookup form the captured context of the function item that fn:function-lookup returns.

[Definition] For a ·context-dependent· function, the parts of the context on which it depends are referred to as implicit arguments.

[Definition] A function that is guaranteed to produce ·identical· results from repeated calls within a single ·execution scope· if the explicit and ·implicit· arguments are identical is referred to as deterministic.

[Definition] A function that is not ·deterministic· is referred to as nondeterministic.

All functions defined in this specification are ·deterministic· unless otherwise stated. Exceptions include the following:

[Definition] Some functions (such as fn:distinct-values, fn:unordered, map:keys, and map:for-each) produce results in an ·implementation-defined· or ·implementation-dependent· order. In such cases two calls with the same arguments are not guaranteed to produce the results in the same order. These functions are said to be nondeterministic with respect to ordering.
Some functions (such as fn:analyze-string, fn:parse-xml, fn:parse-xml-fragment, and fn:json-to-xml) construct a tree of nodes to represent their results. There is no guarantee that repeated calls with the same arguments will return the same identical node (in the sense of the is operator). However, if non-identical nodes are returned, their content will be the same in the sense of the fn:deep-equal function. Such a function is said to be nondeterministic with respect to node identity.
Some functions (such as fn:doc and fn:collection) create new nodes by reading external documents. Such functions are guaranteed to be ·deterministic· with the exception that an implementation is allowed to make them nondeterministic as a user option.

Where the results of a function are described as being (to a greater or lesser extent) ·implementation-defined· or ·implementation-dependent·, this does not by itself remove the requirement that the results should be deterministic: that is, that repeated calls with the same explicit and implicit arguments must return identical results.

2 Accessors

Accessors and their semantics are described in [XQuery and XPath Data Model (XDM) 3.1]. Some of these accessors are exposed to the user through the functions described below.

Each of these functions has an arity-zero signature which is equivalent to the arity-one form, with the context value supplied as the implicit first argument. In addition, each of the arity-one functions accepts an empty sequence as the argument, in which case it generally delivers an empty sequence as the result: the exception is fn:string, which delivers a zero-length string.

Function	Accessor	Accepts	Returns
`fn:node-name`	`node-name`	node (optional)	`xs:QName` (optional)
`fn:nilled`	`nilled`	node (optional)	`xs:boolean` (optional)
`fn:string`	`string-value`	item (optional)	`xs:string`
`fn:data`	`typed-value`	zero or more items	a sequence of atomic values
`fn:base-uri`	`base-uri`	node (optional)	`xs:anyURI` (optional)
`fn:document-uri`	`document-uri`	node (optional)	`xs:anyURI` (optional)

2.1 fn:node-name

Summary

Returns the name of a node, as an xs:QName.

Signature

`fn:node-name`(
`$node`	`as` `node()?`	`:=` `.`
) `as` `xs:QName?`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If the argument is omitted, it defaults to the context value (.). The behavior of the function if the argument is omitted is exactly the same as if the context value had been passed as the argument.

If $node is the empty sequence, the empty sequence is returned.

Otherwise, the function returns the result of the dm:node-name accessor as defined in [XQuery and XPath Data Model (XDM) 3.1] (see Section 4.10 node-name Accessor^DM40).

Error Conditions

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP.
If the context value is not a single node, type error [err:XPTY0004]^XP.

Notes

For element and attribute nodes, the name of the node is returned as an xs:QName, retaining the prefix, namespace URI, and local part.

For processing instructions, the name of the node is returned as an xs:QName in which the prefix and namespace URI are absent^DM40.

For a namespace node, the function returns an empty sequence if the node represents the default namespace; otherwise it returns an xs:QName in which prefix and namespace URI are absent^DM40 and the local part is the namespace prefix being bound.

For all other kinds of node, the function returns the empty sequence.

Examples

Variables
let $e := <doc> <p id="alpha" xml:id="beta">One</p> <p id="gamma" xmlns="http://example.com/ns">Two</p> <ex:p id="delta" xmlns:ex="http://example.com/ns">Three</ex:p> <?pi 3.14159?> </doc>

Expression	Result
`node-name($e//*[@id = 'alpha'])`	fn:QName("", "p")
`node-name($e//*[@id = 'gamma'])`	fn:QName("http://example.com/ns", "p")
`node-name($e//*[@id = 'delta'])`	fn:QName("http://example.com/ns", "ex:p")
`node-name($e//processing-instruction()[1])`	fn:QName("", "pi")
`node-name($e//*[@id = 'alpha']/text())`	()
`node-name($e//*[@id = 'alpha']/@id)`	fn:QName("", "id")
`node-name($e//*[@id = 'alpha']/@xml:id)`	fn:QName("http://www.w3.org/XML/1998/namespace", "xml:id")

2.2 fn:nilled

Summary

Returns true for an element that is nilled.

Signature

`fn:nilled`(
`$node`	`as` `node()?`	`:=` `.`
) `as` `xs:boolean?`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $node is the empty sequence, the function returns the empty sequence.

Otherwise the function returns the result of the dm:nilled accessor as defined in [XQuery and XPath Data Model (XDM) 3.1] (see Section 4.8 nilled Accessor^DM40).

Error Conditions

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Notes

If $node is not an element node, the function returns the empty sequence.

If $node is an untyped element node, the function returns false.

In practice, the function returns true only for an element node that has the attribute xsi:nil="true" and that is successfully validated against a schema that defines the element to be nillable; the detailed rules, however, are defined in [XQuery and XPath Data Model (XDM) 3.1].

2.3 fn:string

Summary

Returns the value of $value represented as an xs:string.

Signature

`fn:string`(
`$value`	`as` `item()?`	`:=` `.`
) `as` `xs:string`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

In the zero-argument version of the function, $value defaults to the context value. That is, calling fn:string() is equivalent to calling fn:string(.).

If $value is the empty sequence, the function returns the zero-length string.

If $value is a node, the function returns the string value of the node, as obtained using the dm:string-value accessor defined in [XQuery and XPath Data Model (XDM) 3.1] (see Section 4.12 string-value Accessor^DM40).

If $value is an atomic value, the function returns the result of the expression $value cast as xs:string (see 21 Casting).

In all other cases, a dynamic error occurs (see below).

Error Conditions

The following errors may be raised when $value is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP.
If the context value is not a single item, type error [err:XPTY0004]^XP.

A type error is raised [err:FOTY0014] if $value is a function item (this includes maps and arrays).

Notes

Every node has a string value, even an element with element-only content (which has no typed value). Moreover, casting an atomic value to a string always succeeds. Functions, maps, and arrays have no string value, so these are the only arguments that satisfy the type signature but cause failure.

Examples

Variables
let $para := <para>In a hole in the ground there lived a <term author="Tolkien">hobbit</term>.</para>

Expression	Result
`string(23)`	"23"
`string(false())`	"false"
`string("Paris")`	"Paris"
`string((1, 2, 3))`	Raises error XPTY0004.
`string([[1, 2], [3, 4]])`	Raises error FOTY0014.
`string(abs#1)`	Raises error FOTY0014.
`string($para)`	"In a hole in the ground there lived a hobbit."

2.4 fn:data

Summary

Returns the result of atomizing a sequence. This process flattens arrays, and replaces nodes by their typed values.

Signature

`fn:data`(
`$input`	`as` `item()*`	`:=` `.`
) `as` `xs:anyAtomicType*`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The result of fn:data is the sequence of atomic values produced by applying the following rules to each item in $input:

If the item is an atomic value, it is appended to the result sequence.
If the item is a node, the typed value of the node is appended to the result sequence. The typed value is a sequence of zero or more atomic values: specifically, the result of the dm:typed-value accessor as defined in [XQuery and XPath Data Model (XDM) 3.1] (See Section 4.14 typed-value Accessor^DM40).
If the item is an array, the result of applying fn:data to each member of the array, in order, is appended to the result sequence.

Error Conditions

A type error is raised [err:FOTY0012] if an item in the sequence $input is a node that does not have a typed value.

A type error is raised [err:FOTY0013] if an item in the sequence $input is a function item other than an array.

A type error is raised [err:XPDY0002]^XP if $input is omitted and the context value is absent^DM40.

Notes

The process of applying the fn:data function to a sequence is referred to as atomization. In many cases an explicit call on fn:data is not required, because atomization is invoked implicitly when a node or sequence of nodes is supplied in a context where an atomic value or sequence of atomic values is required.

The result of atomizing an empty sequence is an empty sequence.

The result of atomizing an empty array is an empty sequence.

Examples

Variables
let $para := <para>In a hole in the ground there lived a <term author="Tolkien">hobbit</term>.</para>

Expression	Result
`data(123)`	123
`data((123, 456))`	123, 456
`data([[1,2],[3,4]])`	1, 2, 3, 4
`data($para)`	xs:untypedAtomic("In a hole in the ground there lived a hobbit.")
`data($para/term/@author)`	xs:untypedAtomic("Tolkien")
`data(abs#1)`	Raises error FOTY0013.

2.5 fn:base-uri

Summary

Returns the base URI of a node.

Signature

`fn:base-uri`(
`$node`	`as` `node()?`	`:=` `.`
) `as` `xs:anyURI?`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The zero-argument version of the function returns the base URI of the context node: it is equivalent to calling fn:base-uri(.).

The single-argument version of the function behaves as follows:

If $node is the empty sequence, the function returns the empty sequence.
Otherwise, the function returns the value of the dm:base-uri accessor applied to the node $node. This accessor is defined, for each kind of node, in the XDM specification (See Section 4.2 base-uri Accessor^DM40).

Note:

As explained in XDM, document, element and processing-instruction nodes have a base-uri property which may be empty. The base-uri property for all other node kinds is the empty sequence. The dm:base-uri accessor returns the base-uri property of a node if it exists and is non-empty; otherwise it returns the result of applying the dm:base-uri accessor to its parent, recursively. If the node does not have a parent, or if the recursive ascent up the ancestor chain encounters a parentless node whose base-uri property is empty, the empty sequence is returned. In the case of namespace nodes, however, the result is always an empty sequence — it does not depend on the base URI of the parent element.

2.6 fn:document-uri

Summary

Returns the URI of a resource where a document can be found, if available.

Signature

`fn:document-uri`(
`$node`	`as` `node()?`	`:=` `.`
) `as` `xs:anyURI?`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $node is the empty sequence, the function returns the empty sequence.

If $node is not a document node, the function returns the empty sequence.

Otherwise, the function returns the value of the document-uri accessor applied to $node, as defined in [XQuery and XPath Data Model (XDM) 3.1] (See Section 5.1.2 Accessors^DM40).

Error Conditions

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Notes

In the case of a document node $D returned by the fn:doc function, it will generally be the case that fn:document-uri($D) returns a URI $U such that a call on fn:doc($U) in the same dynamic context will return the same document node $D. The URI $U will not necessarily be the same URI that was originally passed to the fn:doc function, since several URIs may identify the same resource.

This equivalence does not apply if the second call on fn:doc uses a different dynamic context. For example, in XSLT, a call on fn:doc in one stylesheet package might perform whitespace stripping or schema validation, while the same call in a different stylesheet package does not; the two calls might therefore return different documents both having the same fn:document-uri property.

It is recommended that implementations of fn:collection should follow the same principle: any documents included in the returned collection, if they have a non-empty fn:document-uri property, should be such that a call on fn:doc supplying this URI (in the same dynamic context) returns the same document node.

The same guarantees do not hold for document nodes obtained by other mechanisms, for example document nodes supplied as external parameters to a query or stylesheet. The fn:document-uri property of such documents is under user control; it is entirely possible for two such documents to have the same fn:document-uri property, in which case it is clearly impossible to use this property to retrieve the original document.

3 Errors and diagnostics

3.1 Raising errors

In this document, as well as in [XQuery 4.1: An XML Query Language] and [XML Path Language (XPath) 4.0], the phrase “an error is raised” is used. Raising an error is equivalent to calling the fn:error function defined in this section with the provided error code. Except where otherwise specified, errors defined in this specification are dynamic errors. Some errors, however, are classified as type errors. Type errors are typically used where the presence of the error can be inferred from knowledge of the type of the actual arguments to a function, for example with a call such as fn:string(fn:abs#1). Host languages may allow type errors to be reported statically if they are discovered during static analysis.

When function specifications indicate that an error is to be raised, the notation “[error code ]” is used to specify an error code. Each error defined in this document is identified by an xs:QName that is in the http://www.w3.org/2005/xqt-errors namespace, represented in this document by the err prefix. It is this xs:QName that is actually passed as an argument to the fn:error function. Calling this function raises an error. For a more detailed treatment of error handing, see Section 2.3.3 Handling Dynamic Errors ^XP31.

The fn:error function is a general function that may be called as above but may also be called from [XQuery 4.1: An XML Query Language] or [XML Path Language (XPath) 4.0] applications with, for example, an xs:QName argument.

3.1.1 fn:error

Summary

Calling the fn:error function raises an application-defined error.

Signature

`fn:error`(
`$code`	`as` `xs:QName?`	`:=` `()`,
`$description`	`as` `xs:string?`	`:=` `()`,
`$value`	`as` `item()*`	`:=` `.`
) `as` `none`

Properties

This function is ·nondeterministic·, ·context-independent·, and ·focus-independent·.

Rules

This function never returns a value. Instead it always raises an error. The effect of the error is identical to the effect of dynamic errors raised implicitly, for example when an incorrect argument is supplied to a function.

The parameters to the fn:error function supply information that is associated with the error condition and that is made available to a caller that asks for information about the error. The error may be caught either by the host language (using a try/catch construct in XSLT or XQuery, for example), or by the calling application or external processing environment. The way in which error information is returned to the external processing environment is ·implementation-dependent·.

There are three pieces of information that may be associated with an error.

The $code is an error code that distinguishes this error from others. It is an xs:QName; the namespace URI conventionally identifies the component, subsystem, or authority responsible for defining the meaning of the error code, while the local part identifies the specific error condition. The namespace URI http://www.w3.org/2005/xqt-errors is used for errors defined in this specification; other namespace URIs may be used for errors defined by the application.

If the external processing environment expects the error code to be returned as a URI or a string rather than as an xs:QName, then an error code with namespace URI NS and local part LP will be returned in the form NS#LP. The namespace URI part of the error code should therefore not include a fragment identifier.

If no value is supplied for the $code argument, or if the value supplied is an empty sequence, the effective value of the error code is fn:QName('http://www.w3.org/2005/xqt-errors', 'err:FOER0000').
The $description is a natural-language description of the error condition.

If no value is supplied for the $description argument, or if the value supplied is an empty sequence, then the effective value of the description is ·implementation-dependent·.
The $value is an arbitrary value used to convey additional information about the error, and may be used in any way the application chooses.

If no value is supplied for the $value argument or if the value supplied is an empty sequence, then the effective value of the error object is ·implementation-dependent·.

Error Conditions

This function always raises a dynamic error. By default, it raises [err:FOER0000]

Notes

The value of the $description parameter may need to be localized.

The type “none” is a special type defined in [XQuery 1.0 and XPath 2.0 Formal Semantics] and is not available to the user. It indicates that the function never returns and ensures that it has the correct static type.

Any QName may be used as an error code; there are no reserved names or namespaces. The error is always classified as a dynamic error, even if the error code used is one that is normally used for static errors or type errors.

Examples

Expression:	`error()`
Result:	Raises error FOER0000. (This returns the URI `http://www.w3.org/2005/xqt-errors#FOER0000` (or the corresponding `xs:QName`) to the external processing environment, unless the error is caught using a try/catch construct in the host language.)
Expression:	error( QName( 'http://www.example.com/HR', 'myerr:toohighsal' ), 'Salary is too high' )
Result:	Raises error myerr:toohighsal. (This returns `http://www.example.com/HR#toohighsal` and the `xs:string` `"Salary is too high"` (or the corresponding `xs:QName`) to the external processing environment, unless the error is caught using a try/catch construct in the host language.)

History

Changed in 4.0: All three arguments are now optional, and each argument can be set to an empty sequence. Previously if $description was supplied, it could not be empty.

3.2 Diagnostic tracing

3.2.1 fn:trace

Summary

Provides an execution trace intended to be used in debugging queries.

Signature

`fn:trace`(
`$input`	`as` `item()*`,
`$label`	`as` `xs:string?`	`:=` `()`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns $input, unchanged.

In addition, the values of $input, typically serialized and converted to an xs:string, and $label (if supplied and non-empty) may be output to an ·implementation-defined· destination.

Any serialization of the implementation's trace output must not raise an error. This can be achieved (for example) by using a serialization method that can handle arbitrary input, such as the adaptive output method (see Section 10 Adaptive Output Method ^SER31).

The format of the trace output and its order are ·implementation-dependent·. Therefore, the order in which the output appears is not predictable. This also means that if dynamic errors occur (whether or not they are caught using try/catch), it may be unpredictable whether any output is reported before the error occurs.

Notes

If the trace information is unrelated to a specific value, fn:message can be used instead.

Examples

Consider a situation in which a user wants to investigate the actual value passed to a function. Assume that in a particular execution, `$v` is an `xs:decimal` with value `124.84`. Writing `fn:trace($v, 'the value of $v is:')` will return `$v`. The processor may output `"124.84"` and `"the value of $v is:"` to an ·implementation-defined· destination.
The following two XPath expressions are identical, but only the second provides trace feedback to the user:
`//book[xs:decimal(@price) gt 100]` `//book[xs:decimal(@price) gt 100] => trace('books more expensive than €100:')`

History

Changed in 4.0: The $label argument can now be set to an empty sequence. Previously if $label was supplied, it could not be empty.

3.2.2 fn:message

Summary

Outputs trace information and discards the result.

Signature

`fn:message`(
`$input`	`as` `item()*`,
`$label`	`as` `xs:string?`	`:=` `()`
) `as` `empty-sequence()`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Similar to fn:trace, the values of $input, typically serialized and converted to an xs:string, and $label (if supplied and non-empty) may be output to an ·implementation-defined· destination.

In contrast to fn:trace, the function returns an empty sequence.

Any serialization of the implementation’s log output must not raise an error. This can e.g. be achieved by using a serialization method that can handle arbitrary input, such as the Section 10 Adaptive Output Method ^SER31.

The format of the log output and its order are ·implementation-dependent·. Therefore, the order in which the output appears is not predictable. This also means that if dynamic errors occur (whether or not they are caught using try/catch), it may be unpredictable whether any output is logged before the error occurs.

Notes

The function can be used for debugging. It can also be helpful in productive environments, e.g. to store dynamic input and evaluations to log files.

Examples

The following two XPath expressions are identical, but only the second logs any feedback:
`//book[xs:decimal(@price) lt 1000]` `//book[if (xs:decimal(@price) lt 1000) then true() else message(@price, @title \|\| ' is unexpectedly expensive: ')]`

History

New function.

3.2.3 fn:stack-trace

Summary

Returns implementation-dependent information about the current state of execution.

Signature

fn:stack-trace() as xs:string

Properties

This function is ·nondeterministic·, ·context-independent·, and ·focus-independent·.

Rules

The result of the function is an ·implementation-dependent· string containing diagnostic information about the current state of execution.

The function is nondeterministic: multiple calls will typically produce different results.

Notes

The function will typically be called to assist in diagnosing dynamic errors.

4 Functions and operators on numerics

This section specifies arithmetic operators on the numeric datatypes defined in [XML Schema Part 2: Datatypes Second Edition].

4.1 Numeric types

The operators described in this section are defined on the following atomic types.

- decimal
  - integer
- double
- float

Legend:

Supertype
- subtype

Built-in atomic types

They also apply to types derived by restriction from the above types.

The type xs:numeric is defined as a union type whose member types are (in order) xs:double, xs:float, and xs:decimal. This type is implicitly imported into the static context, so it can also be used in defining the signature of user-written functions. Apart from the fact that it is implicitly imported, it behaves exactly like a user-defined type with the same definition. This means, for example:

If the expected type of a function parameter is given as xs:numeric, the actual value supplied can be an instance of any of these three types, or any type derived from these three by restriction (this includes the built-in type xs:integer, which is derived from xs:decimal).
If the expected type of a function parameter is given as xs:numeric, and the actual value supplied is xs:untypedAtomic (or a node whose atomized value is xs:untypedAtomic), then it will be cast to the union type xs:numeric using the rules in 21.3.5 Casting to union types. Because the lexical space of xs:double subsumes the lexical space of the other member types, and xs:double is listed first, the effect is that if the untyped atomic value is in the lexical space of xs:double, it will be converted to an xs:double, and if not, a dynamic error occurs.
When the return type of a function is given as xs:numeric, the actual value returned will be an instance of one of the three member types (and perhaps also of types derived from these by restriction). The rules for the particular function will specify how the type of the result depends on the values supplied as arguments. In many cases, for the functions in this specification, the result is defined to be the same type as the first argument.

Note:

This specification uses [IEEE 754-2008] arithmetic for xs:float and xs:double values. One consequence of this is that some operations result in the value NaN (not a number), which has the unusual property that it is not equal to itself. Another consequence is that some operations return the value negative zero. This differs from [XML Schema Part 2: Datatypes Second Edition], which defines NaN as being equal to itself and defines only a single zero in the value space. The text accompanying several functions defines behavior for both positive and negative zero inputs and outputs in the interest of alignment with [IEEE 754-2008]. A conformant implementation must respect these semantics. In consequence, the expression -0.0e0 (which is actually a unary minus operator applied to an xs:double value) will always return negative zero: see 4.2.8 op:numeric-unary-minus. As a concession to implementations that rely on implementations of XSD 1.0, however, when casting from string to double the lexical form -0 may be converted to positive zero, though negative zero is recommended.

XML Schema 1.1 introduces support for positive and negative zero as distinct values, and also uses the [IEEE 754-2008] semantics for comparisons involving NaN.

4.2 Arithmetic operators on numeric values

The following functions define the semantics of arithmetic operators defined in [XQuery 4.1: An XML Query Language] and [XML Path Language (XPath) 4.0] on these numeric types.

Operator	Meaning
`op:numeric-add`	Addition
`op:numeric-subtract`	Subtraction
`op:numeric-multiply`	Multiplication
`op:numeric-divide`	Division
`op:numeric-integer-divide`	Integer division
`op:numeric-mod`	Modulus
`op:numeric-unary-plus`	Unary plus
`op:numeric-unary-minus`	Unary minus (negation)

The parameters and return types for the above operators are in most cases declared to be of type xs:numeric, which permits the basic numeric types: xs:integer, xs:decimal, xs:float and xs:double, and types derived from them. In general the two-argument functions require that both arguments are of the same primitive type, and they return a value of this same type. The exceptions are op:numeric-divide, which returns an xs:decimal if called with two xs:integer operands, and op:numeric-integer-divide which always returns an xs:integer.

If the two operands of an arithmetic expression are not of the same type, subtype substitution and numeric type promotion are used to obtain two operands of the same type. Section B.1 Type Promotion ^XP31 and Section B.2 Operator Mapping ^XP31 describe the semantics of these operations in detail.

The result type of operations depends on their argument datatypes and is defined in the following table:

Operator	Returns
`op:operation(xs:integer, xs:integer)`	`xs:integer` (except for `op:numeric-divide(integer, integer)`, which returns `xs:decimal`)
`op:operation(xs:decimal, xs:decimal)`	`xs:decimal`
`op:operation(xs:float, xs:float)`	`xs:float`
`op:operation(xs:double, xs:double)`	`xs:double`
`op:operation(xs:integer)`	`xs:integer`
`op:operation(xs:decimal)`	`xs:decimal`
`op:operation(xs:float)`	`xs:float`
`op:operation(xs:double)`	`xs:double`

These rules define any operation on any pair of arithmetic types. Consider the following example:

op:operation(xs:int, xs:double) => op:operation(xs:double, xs:double)

For this operation, xs:int must be converted to xs:double. This can be done, since by the rules above: xs:int can be substituted for xs:integer, xs:integer can be substituted for xs:decimal, xs:decimal can be promoted to xs:double. As far as possible, the promotions should be done in a single step. Specifically, when an xs:decimal is promoted to an xs:double, it should not be converted to an xs:float and then to xs:double, as this risks loss of precision.

As another example, a user may define height as a derived type of xs:integer with a minimum value of 20 and a maximum value of 100. They may then derive fenceHeight using an enumeration to restrict the permitted set of values to, say, 36, 48 and 60.

op:operation(fenceHeight, xs:integer) => op:operation(xs:integer, xs:integer)

fenceHeight can be substituted for its base type height and height can be substituted for its base type xs:integer.

The basic rules for addition, subtraction, and multiplication of ordinary numbers are not set out in this specification; they are taken as given. In the case of xs:double and xs:float the rules are as defined in [IEEE 754-2008]. The rules for handling division and modulus operations, as well as the rules for handling special values such as infinity and NaN, and exception conditions such as overflow and underflow, are described more explicitly since they are not necessarily obvious.

On overflow and underflow situations during arithmetic operations, conforming implementations must behave as follows:

For xs:float and xs:double operations, overflow behavior must be conformant with [IEEE 754-2008]. This specification allows the following options:
- Raising a dynamic error [err:FOAR0002] via an overflow trap.
- Returning INF or -INF.
- Returning the largest (positive or negative) non-infinite number.
For xs:float and xs:double operations, underflow behavior must be conformant with [IEEE 754-2008]. This specification allows the following options:
- Raising a dynamic error [err:FOAR0002] via an underflow trap.
- Returning 0.0E0 or +/- 2**Emin or a denormalized value; where Emin is the smallest possible xs:float or xs:double exponent.
For xs:decimal operations, overflow behavior must raise a dynamic error [err:FOAR0002]. On underflow, 0.0 must be returned.
For xs:integer operations, implementations that support limited-precision integer operations must select from the following options:
- They may choose to always raise a dynamic error [err:FOAR0002].
- They may provide an ·implementation-defined· mechanism that allows users to choose between raising an error and returning a result that is modulo the largest representable integer value. See [ISO 10967].

The functions op:numeric-add, op:numeric-subtract, op:numeric-multiply, op:numeric-divide, op:numeric-integer-divide and op:numeric-mod are each defined for pairs of numeric operands, each of which has the same type:xs:integer, xs:decimal, xs:float, or xs:double. The functions op:numeric-unary-plus and op:numeric-unary-minus are defined for a single operand whose type is one of those same numeric types.

For xs:float and xs:double arguments, if either argument is NaN, the result is NaN.

For xs:decimal values, let N be the number of digits of precision supported by the implementation, and let M (M <= N) be the minimum limit on the number of digits required for conformance (18 digits for XSD 1.0, 16 digits for XSD 1.1). Then for addition, subtraction, and multiplication operations, the returned result should be accurate to N digits of precision, and for division and modulus operations, the returned result should be accurate to at least M digits of precision. The actual precision is ·implementation-defined·. If the number of digits in the mathematical result exceeds the number of digits that the implementation retains for that operation, the result is truncated or rounded in an ·implementation-defined· manner.

Note:

This specification does not determine whether xs:decimal operations are fixed point or floating point. In an implementation using floating point it is possible for very simple operations to require more digits of precision than are available; for example, adding 1e100 to 1e-100 requires 200 digits of precision for an accurate representation of the result.

The [IEEE 754-2008] specification also describes handling of two exception conditions called divideByZero and invalidOperation. The IEEE divideByZero exception is raised not only by a direct attempt to divide by zero, but also by operations such as log(0). The IEEE invalidOperation exception is raised by attempts to call a function with an argument that is outside the function’s domain (for example, sqrt(-1) or log(-1)). Although IEEE defines these as exceptions, it also defines “default non-stop exception handling” in which the operation returns a defined result, typically positive or negative infinity, or NaN. With this function library, these IEEE exceptions do not cause a dynamic error at the application level; rather they result in the relevant function or operator returning the defined non-error result. The underlying IEEE exception may be notified to the application or to the user by some ·implementation-defined· warning condition, but the observable effect on an application using the functions and operators defined in this specification is simply to return the defined result (typically -INF, +INF, or NaN) with no error.

The [IEEE 754-2008] specification distinguishes two NaN values: a quiet NaN and a signaling NaN. These two values are not distinguishable in the XDM model: the value spaces of xs:float and xs:double each include only a single NaN value. This does not prevent the implementation distinguishing them internally, and triggering different ·implementation-defined· warning conditions, but such distinctions do not affect the observable behavior of an application using the functions and operators defined in this specification.

4.2.1 op:numeric-add

Summary

Returns the arithmetic sum of its operands: ($arg1 + $arg2).

Operator Mapping

Defines the semantics of the + operator when applied to two numeric values

Signature

`op:numeric-add`(
`$arg1`	`as` `xs:numeric`,
`$arg2`	`as` `xs:numeric`
) `as` `xs:numeric`

Rules

General rules: see 4.2 Arithmetic operators on numeric values.

Notes

For xs:float or xs:double values, if one of the operands is a zero or a finite number and the other is INF or -INF, INF or -INF is returned. If both operands are INF, INF is returned. If both operands are -INF, -INF is returned. If one of the operands is INF and the other is -INF, NaN is returned.

4.2.2 op:numeric-subtract

Summary

Returns the arithmetic difference of its operands: ($arg1 - $arg2).

Operator Mapping

Defines the semantics of the - operator when applied to two numeric values.

Signature

`op:numeric-subtract`(
`$arg1`	`as` `xs:numeric`,
`$arg2`	`as` `xs:numeric`
) `as` `xs:numeric`

Rules

General rules: see 4.2 Arithmetic operators on numeric values.

Notes

For xs:float or xs:double values, if one of the operands is a zero or a finite number and the other is INF or -INF, an infinity of the appropriate sign is returned. If both operands are INF or -INF, NaN is returned. If one of the operands is INF and the other is -INF, an infinity of the appropriate sign is returned.

4.2.3 op:numeric-multiply

Summary

Returns the arithmetic product of its operands: ($arg1 * $arg2).

Operator Mapping

Defines the semantics of the * operator when applied to two numeric values.

Signature

`op:numeric-multiply`(
`$arg1`	`as` `xs:numeric`,
`$arg2`	`as` `xs:numeric`
) `as` `xs:numeric`

Rules

General rules: see 4.2 Arithmetic operators on numeric values.

Notes

For xs:float or xs:double values, if one of the operands is a zero and the other is an infinity, NaN is returned. If one of the operands is a non-zero number and the other is an infinity, an infinity with the appropriate sign is returned.

4.2.4 op:numeric-divide

Summary

Returns the arithmetic quotient of its operands: ($arg1 div $arg2).

Operator Mapping

Defines the semantics of the div operator when applied to two numeric values.

Signature

`op:numeric-divide`(
`$arg1`	`as` `xs:numeric`,
`$arg2`	`as` `xs:numeric`
) `as` `xs:numeric`

Rules

General rules: see 4.2 Arithmetic operators on numeric values.

As a special case, if the types of both $arg1 and $arg2 are xs:integer, then the return type is xs:decimal.

Error Conditions

A dynamic error is raised [err:FOAR0001] for xs:decimal and xs:integer operands, if the divisor is (positive or negative) zero.

Notes

For xs:float and xs:double operands, floating point division is performed as specified in [IEEE 754-2008]. A positive number divided by positive zero returns INF. A negative number divided by positive zero returns -INF. Division by negative zero returns -INF and INF, respectively. Positive or negative zero divided by positive or negative zero returns NaN. Also, INF or -INF divided by INF or -INF returns NaN.

4.2.5 op:numeric-integer-divide

Summary

Performs an integer division.

Operator Mapping

Defines the semantics of the idiv operator when applied to two numeric values.

Signature

`op:numeric-integer-divide`(
`$arg1`	`as` `xs:numeric`,
`$arg2`	`as` `xs:numeric`
) `as` `xs:integer`

Rules

General rules: see 4.2 Arithmetic operators on numeric values.

If $arg2 is INF or -INF, and $arg1 is not INF or -INF, then the result is zero.

Otherwise, subject to limits of precision and overflow/underflow conditions, the result is the largest (furthest from zero) xs:integer value $N such that the following expression is true:

abs($N * $arg2) le abs($arg1) 
               and compare($N * $arg2, 0) eq compare($arg1, 0).

Note:

The second term in this condition ensures that the result has the correct sign.

The implementation may adopt a different algorithm provided that it is equivalent to this formulation in all cases where ·implementation-dependent· or ·implementation-defined· behavior does not affect the outcome, for example, the implementation-defined precision of the result of xs:decimal division.

Error Conditions

A dynamic error is raised [err:FOAR0001] if the divisor is (positive or negative) zero.

A dynamic error is raised [err:FOAR0002] if either operand is NaN or if $arg1 is INF or -INF.

Notes

Except in situations involving errors, loss of precision, or overflow/underflow, the result of $a idiv $b is the same as ($a div $b) cast as xs:integer.

The semantics of this function are different from integer division as defined in programming languages such as Java and C++.

Examples

Expression	Result
`op:numeric-integer-divide(10,3)`	3
`op:numeric-integer-divide(3,-2)`	-1
`op:numeric-integer-divide(-3,2)`	-1
`op:numeric-integer-divide(-3,-2)`	1
`op:numeric-integer-divide(9.0,3)`	3
`op:numeric-integer-divide(-3.5,3)`	-1
`op:numeric-integer-divide(3.0,4)`	0
`op:numeric-integer-divide(3.1E1,6)`	5
`op:numeric-integer-divide(3.1E1,7)`	4

4.2.6 op:numeric-mod

Summary

Returns the remainder resulting from dividing $arg1, the dividend, by $arg2, the divisor.

Operator Mapping

Defines the semantics of the mod operator when applied to two numeric values.

Signature

`op:numeric-mod`(
`$arg1`	`as` `xs:numeric`,
`$arg2`	`as` `xs:numeric`
) `as` `xs:numeric`

Rules

General rules: see 4.2 Arithmetic operators on numeric values.

The operation a mod b for operands that are xs:integer or xs:decimal, or types derived from them, produces a result such that (a idiv b)*b+(a mod b) is equal to a and the magnitude of the result is always less than the magnitude of b. This identity holds even in the special case that the dividend is the negative integer of largest possible magnitude for its type and the divisor is -1 (the remainder is 0). It follows from this rule that the sign of the result is the sign of the dividend.

For xs:float and xs:double operands the following rules apply:

If either operand is NaN, the result is NaN.
If the dividend is positive or negative infinity, or the divisor is positive or negative zero (0), or both, the result is NaN.
If the dividend is finite and the divisor is an infinity, the result equals the dividend.
If the dividend is positive or negative zero and the divisor is finite, the result is the same as the dividend.
In the remaining cases, where neither positive or negative infinity, nor positive or negative zero, nor NaN is involved, the result obeys (a idiv b)*b+(a mod b) = a. Division is truncating division, analogous to integer division, not [IEEE 754-2008] rounding division i.e. additional digits are truncated, not rounded to the required precision.

Error Conditions

A dynamic error is raised [err:FOAR0001] for xs:integer and xs:decimal operands, if $arg2 is zero.

Examples

Expression	Result
`op:numeric-mod(10,3)`	1
`op:numeric-mod(6,-2)`	0
`op:numeric-mod(4.5,1.2)`	0.9
`op:numeric-mod(1.23E2, 0.6E1)`	3.0E0

4.2.7 op:numeric-unary-plus

Summary

Returns its operand with the sign unchanged: (+ $arg).

Operator Mapping

Defines the semantics of the unary + operator applied to a numeric value.

Signature

`op:numeric-unary-plus`(
`$arg`	`as` `xs:numeric`
) `as` `xs:numeric`

Rules

General rules: see 4.2 Arithmetic operators on numeric values.

The returned value is equal to $arg, and is an instance of xs:integer, xs:decimal, xs:double, or xs:float depending on the type of $arg.

Notes

Because function conversion rules are applied in the normal way, the unary + operator can be used to force conversion of an untyped node to a number: the result of +@price is the same as xs:double(@price) if the type of @price is xs:untypedAtomic.

4.2.8 op:numeric-unary-minus

Summary

Returns its operand with the sign reversed: (- $arg).

Operator Mapping

Defines the semantics of the unary - operator when applied to a numeric value.

Signature

`op:numeric-unary-minus`(
`$arg`	`as` `xs:numeric`
) `as` `xs:numeric`

Rules

General rules: see 4.2 Arithmetic operators on numeric values.

The returned value is an instance of xs:integer, xs:decimal, xs:double, or xs:float depending on the type of $arg.

For xs:integer and xs:decimal arguments, 0 and 0.0 return 0 and 0.0, respectively. For xs:float and xs:double arguments, NaN returns NaN, 0.0E0 returns -0.0E0 and vice versa. INF returns -INF. -INF returns INF.

4.3 Comparison operators on numeric values

The six value comparison operators eq, ne, lt, le, gt, and ge are defined in terms of two underlying functions: op:numeric-equal and op:numeric-less-than. These functions are defined to operate on values of the same type.

If the arguments are of different types, one argument is promoted to the type of the other as described above in 4.2 Arithmetic operators on numeric values. Each comparison operator returns a boolean value. If either, or both, operands are NaN, false is returned.

Note:

For a description of the different ways of comparing numeric values using the operators = and eq and the functions fn:deep-equal and fn:atomic-equal, see Section H Atomic Comparisons: An Overview (Non-Normative)^XP40.

Note:

Function	Meaning
`op:numeric-equal`	Returns `true` if and only if the value of `$arg1` is equal to the value of `$arg2`.
`op:numeric-less-than`	Returns `true` if and only if `$arg1` is numerically less than `$arg2`.

4.3.1 op:numeric-equal

Summary

Returns true if and only if the value of $arg1 is equal to the value of $arg2.

Operator Mapping

Defines the semantics of the eq operator when applied to two numeric values, and is also used in defining the semantics of ne, le and ge.

Signature

`op:numeric-equal`(
`$arg1`	`as` `xs:numeric`,
`$arg2`	`as` `xs:numeric`
) `as` `xs:boolean`

Rules

General rules: see 4.2 Arithmetic operators on numeric values and 4.3 Comparison operators on numeric values.

Notes

For xs:float and xs:double values, positive zero and negative zero compare equal. INF equals INF and -INF equals -INF. If $arg1 or $arg2 is NaN, the function returns false.

4.3.2 op:numeric-less-than

Summary

Returns true if and only if $arg1 is numerically less than $arg2.

Operator Mapping

Defines the semantics of the lt operator when applied to two numeric values, and is also used in defining the semantics of le, gt, and ge.

Signature

`op:numeric-less-than`(
`$arg1`	`as` `xs:numeric`,
`$arg2`	`as` `xs:numeric`
) `as` `xs:boolean`

Rules

General rules: see 4.2 Arithmetic operators on numeric values and 4.3 Comparison operators on numeric values.

Notes

For xs:float and xs:double values, positive infinity is greater than all other non-NaN values; negative infinity is less than all other non-NaN values. Positive and negative zero compare equal. If $arg1 or $arg2 is NaN, the function returns false.

4.4 Functions on numeric values

The following functions are defined on numeric types. Each function returns a value of the same type as the type of its argument.

If the argument is the empty sequence, the empty sequence is returned.
For xs:float and xs:double arguments, if the argument is NaN, NaN is returned.
With the exception of fn:abs, functions with arguments of type xs:float and xs:double that are positive or negative infinity return positive or negative infinity.

Function	Meaning
`fn:abs`	Returns the absolute value of `$value`.
`fn:ceiling`	Rounds `$value` upwards to a whole number.
`fn:floor`	Rounds `$value` downwards to a whole number.
`fn:round`	Rounds a value to a specified number of decimal places, rounding upwards if two such values are equally near.
`fn:round-half-to-even`	Rounds a value to a specified number of decimal places, rounding to make the last digit even if two such values are equally near.
`fn:is-NaN`	Returns `true` if the argument is the `xs:float` or `xs:double` value `NaN`.

Note:

fn:round and fn:round-half-to-even produce the same result in all cases except when the argument is exactly midway between two values with the required precision.

Other ways of rounding midway values can be achieved as follows:

Towards negative infinity: -fn:round(-$x)
Away from zero: fn:round(fn:abs($x))*fn:compare($x,0)
Towards zero: fn:abs(fn:round(-$x))*-fn:compare($x,0)

4.4.1 fn:abs

Summary

Returns the absolute value of $value.

Signature

`fn:abs`(
`$value`	`as` `xs:numeric?`
) `as` `xs:numeric?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

General rules: see 4.4 Functions on numeric values.

If $value is negative the function returns -$value, otherwise it returns $value.

For the four types xs:float, xs:double, xs:decimal and xs:integer, it is guaranteed that if the type of $value is an instance of type T then the result will also be an instance of T. The result may also be an instance of a type derived from one of these four by restriction. For example, if $value is an instance of xs:positiveInteger then the value of $value may be returned unchanged.

For xs:float and xs:double arguments, if the argument is positive zero or negative zero, then positive zero is returned. If the argument is positive or negative infinity, positive infinity is returned.

Examples

Expression	Result
`abs(10.5)`	10.5
`abs(-10.5)`	10.5
`abs(-math:log(0))`	xs:double('INF')

4.4.2 fn:ceiling

Summary

Rounds $value upwards to a whole number.

Signature

`fn:ceiling`(
`$value`	`as` `xs:numeric?`
) `as` `xs:numeric?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

General rules: see 4.4 Functions on numeric values.

The function returns the smallest (closest to negative infinity) number with no fractional part that is not less than $value.

For the four types xs:float, xs:double, xs:decimal and xs:integer, it is guaranteed that if the type of $value is an instance of type T then the result will also be an instance of T. The result may also be an instance of a type derived from one of these four by restriction. For example, if $value is an instance of xs:decimal then the result may be an instance of xs:integer.

For xs:float and xs:double arguments, if the argument is positive zero, then positive zero is returned. If the argument is negative zero, then negative zero is returned. If the argument is less than zero and greater than -1, negative zero is returned. If the argument is positive or negative infinity, the value of the argument is returned.

Examples

Expression	Result
`ceiling(10.5)`	11
`ceiling(-10.5)`	-10
`ceiling(math:log(0))`	-xs:double('INF')

4.4.3 fn:floor

Summary

Rounds $value downwards to a whole number.

Signature

`fn:floor`(
`$value`	`as` `xs:numeric?`
) `as` `xs:numeric?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

General rules: see 4.4 Functions on numeric values.

The function returns the largest (closest to positive infinity) number with no fractional part that is not greater than $value.

For the four types xs:float, xs:double, xs:decimal and xs:integer, it is guaranteed that if the type of $value is an instance of type T then the result will also be an instance of T. The result may also be an instance of a type derived from one of these four by restriction. For example, if $value is an instance of xs:decimal then the result may be an instance of xs:integer.

For xs:float and xs:double arguments, if the argument is positive zero, then positive zero is returned. If the argument is negative zero, then negative zero is returned. If the argument is positive or negative infinity, the value of the argument is returned.

Examples

Expression	Result
`floor(10.5)`	10
`floor(-10.5)`	-11
`math:log(0) => floor()`	-xs:double('INF')

4.4.4 fn:round

Summary

Rounds a value to a specified number of decimal places, rounding upwards if two such values are equally near.

Signature

`fn:round`(
`$value`	`as` `xs:numeric?`,
`$precision`	`as` `xs:integer?`	`:=` `0`
) `as` `xs:numeric?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

General rules: see 4.4 Functions on numeric values.

The function returns the nearest (that is, numerically closest) value to $value that is a multiple of ten to the power of minus $precision. If two such values are equally near (for example, if the fractional part in $value is exactly .5), the function returns the one that is closest to positive infinity.

For the four types xs:float, xs:double, xs:decimal and xs:integer, it is guaranteed that if the type of $value is an instance of type T then the result will also be an instance of T. The result may also be an instance of a type derived from one of these four by restriction. For example, if $value is an instance of xs:decimal and $precision is less than one, then the result may be an instance of xs:integer.

If the second argument is omitted or an empty sequence, the function produces the same result as the two-argument version with $precision=0 (that is, it rounds to a whole number).

When $value is of type xs:float and xs:double:

If $value is NaN, positive or negative zero, or positive or negative infinity, then the result is the same as the argument.
For other values, the argument is cast to xs:decimal using an implementation of xs:decimal that imposes no limits on the number of digits that can be represented. The function is applied to this xs:decimal value, and the resulting xs:decimal is cast back to xs:float or xs:double as appropriate to form the function result. If the resulting xs:decimal value is zero, then positive or negative zero is returned according to the sign of $value.

Notes

This function is typically used with a non-zero $precision in financial applications where the argument is of type xs:decimal. For arguments of type xs:float and xs:double the results may be counter-intuitive. For example, consider round(35.425e0, 2). The result is not 35.43, as might be expected, but 35.42. This is because the xs:double written as 35.425e0 has an exact value equal to 35.42499999999..., which is closer to 35.42 than to 35.43.

Examples

Expression	Result
`round(2.5)`	3.0
`round(2.4999)`	2.0
`round(-2.5)`	-2.0 (Not the possible alternative, `-3`).
`round(1.125, 2)`	1.13
`round(8452, -2)`	8500
`round(3.1415e0, 2)`	3.14e0
`math:log(0) => round()`	-xs:double('INF')

4.4.5 fn:round-half-to-even

Summary

Rounds a value to a specified number of decimal places, rounding to make the last digit even if two such values are equally near.

Signature

`fn:round-half-to-even`(
`$value`	`as` `xs:numeric?`,
`$precision`	`as` `xs:integer?`	`:=` `0`
) `as` `xs:numeric?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

General rules: see 4.4 Functions on numeric values.

The function returns the nearest (that is, numerically closest) value to $value that is a multiple of ten to the power of minus $precision. If two such values are equally near (e.g. if the fractional part in $value is exactly .500...), the function returns the one whose least significant digit is even.

For the four types xs:float, xs:double, xs:decimal and xs:integer, it is guaranteed that if the type of $value is an instance of type T then the result will also be an instance of T. The result may also be an instance of a type derived from one of these four by restriction. For example, if $value is an instance of xs:decimal and $precision is less than one, then the result may be an instance of xs:integer.

If the second argument is omitted or an empty sequence, the function produces the same result as the two-argument version with $precision=0.

For arguments of type xs:float and xs:double:

If the argument is NaN, positive or negative zero, or positive or negative infinity, then the result is the same as the argument.
In all other cases, the argument is cast to xs:decimal using an implementation of xs:decimal that imposes no limits on the number of digits that can be represented. The function is applied to this xs:decimal value, and the resulting xs:decimal is cast back to xs:float or xs:double as appropriate to form the function result. If the resulting xs:decimal value is zero, then positive or negative zero is returned according to the sign of the original argument.

Notes

This function is typically used in financial applications where the argument is of type xs:decimal. For arguments of type xs:float and xs:double the results may be counter-intuitive. For example, consider round-half-to-even(xs:float(150.015), 2). The result is not 150.02 as might be expected, but 150.01. This is because the conversion of the xs:float value represented by the literal 150.015 to an xs:decimal produces the xs:decimal value 150.014999389..., which is closer to 150.01 than to 150.02.

Examples

Expression	Result
`round-half-to-even(0.5)`	0.0
`round-half-to-even(1.5)`	2.0
`round-half-to-even(2.5)`	2.0
`round-half-to-even(3.567812e+3, 2)`	3567.81e0
`round-half-to-even(4.7564e-3, 2)`	0.0e0
`round-half-to-even(35612.25, -2)`	35600
`math:log(0) => round-half-to-even()`	-xs:double('INF')

4.4.6 fn:is-NaN

Summary

Returns true if the argument is the xs:float or xs:double value NaN.

Signature

`fn:is-NaN`(
`$value`	`as` `xs:anyAtomicType`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns true if the argument is the xs:float or xs:double value NaN; otherwise it returns false.

Examples

Expression	Result
`is-NaN(23)`	false()
`is-NaN("NaN")`	false()
`is-NaN(number("twenty-three"))`	true()
`is-NaN(math:sqrt(-1))`	true()

History

New in 4.0. Accepted 2022-09-20.

4.5 Parsing numbers

It is possible to convert strings to values of type xs:integer, xs:float, xs:decimal, or xs:double using the constructor functions described in 20 Constructor functions or using cast expressions as described in 21 Casting.

In addition the fn:number function is available to convert strings to values of type xs:double. It differs from the xs:double constructor function in that any value outside the lexical space of the xs:double datatype is converted to the xs:double value NaN.

Function	Meaning
`fn:number`	Returns the value indicated by `$value` or, if `$value` is not specified, the context value after atomization, converted to an `xs:double`.
`fn:parse-integer`	Converts a string to an integer, recognizing any radix in the range 2 to 36.

4.5.1 fn:number

Summary

Returns the value indicated by $value or, if $value is not specified, the context value after atomization, converted to an xs:double.

Signature

`fn:number`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:double`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Calling the zero-argument version of the function is defined to give the same result as calling the single-argument version with the context value (.). That is, fn:number() is equivalent to fn:number(.), as defined by the rules that follow.

If $value is the empty sequence or if $value cannot be converted to an xs:double, the xs:double value NaN is returned.

Otherwise, $value is converted to an xs:double following the rules of 21.1.2.2 Casting to xs:double. If the conversion to xs:double fails, the xs:double value NaN is returned.

Error Conditions

A type error is raised [err:XPDY0002]^XP if $value is omitted and the context value is absent^DM40.

As a consequence of the rules given above, a type error is raised [err:XPTY0004]^XP if the context value cannot be atomized, or if the result of atomizing the context value is a sequence containing more than one atomic value.

Notes

XSD 1.1 allows the string +INF as a representation of positive infinity; XSD 1.0 does not. It is ·implementation-defined· whether XSD 1.1 is supported.

Generally fn:number returns NaN rather than raising a dynamic error if the argument cannot be converted to xs:double. However, a type error is raised in the usual way if the supplied argument cannot be atomized or if the result of atomization does not match the required argument type.

Examples

Variables
let $e := <e price="12.1" discount="NONE"/>

Expression	Result
`number(12)`	1.2e1
`number('12')`	1.2e1
`number('INF')`	xs:double('INF')
`number('NaN')`	xs:double('NaN')
`number('non-numeric')`	xs:double('NaN')
`number($e/@price)`	1.21e1
`number($e/@discount)`	xs:double('NaN')
`number($e/@misspelt)`	xs:double('NaN')
`("10", "11", "12")!number()`	1.0e1, 1.1e1, 1.2e1

4.5.2 fn:parse-integer

Summary

Converts a string to an integer, recognizing any radix in the range 2 to 36.

Signature

`fn:parse-integer`(
`$value`	`as` `xs:string`,
`$radix`	`as` `xs:integer?`	`:=` `10`
) `as` `xs:integer`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The supplied $radix must be in the range 2 to 36 inclusive.

The string $value is preprocessed by stripping all whitespace characters (including internal whitespace) and underscore characters.

After this process, the supplied value must consist of an optional sign (+ or -) followed by a sequence of one or more generalized digits drawn from the first $radix characters in the alphabet 0123456789abcdefghijklmnopqrstuvwxyz; upper-case alphabetics A-Z may be used in place of their lower-case equivalents.

The value of a generalized digit corresponds to its position in this alphabet. More formally, in non-error cases the result of the function is given by the XQuery expression:

let $alphabet := characters("0123456789abcdefghijklmnopqrstuvwxyz")
let $preprocessed-value := translate($value, "_ &#x9;&#xa;&#xd;", "")
let $digits := translate($preprocessed-value, "+-", "")
let $abs := sum(
  for $char at $p in reverse(characters($digits))
  return (index-of($alphabet, $char) - 1) * xs:integer(math:pow($radix, $p - 1)))
return if (starts-with($preprocessed-value, "-")) then -$abs else +$abs

Error Conditions

A dynamic error is raised [err:FORG0011] if $radix is not in the range 2 to 36.

A dynamic error is raised [err:FORG0012] if, after stripping whitespace and underscores and the optional leading sign, $value is a zero-length string, or if it contains a character that is not among the first $radix characters in the alphabet 0123456789abcdefghijklmnopqrstuvwxyz, or the upper-case equivalent of such a character.

A dynamic error is raised [err:FOCA0003] if the value of the resulting integer exceeds the implementation-dependent limit on the size of an xs:integer.

Notes

When $radix takes its default value of 10, the function delivers the same result as casting $value (after removal of whitespace and underscores) to xs:integer.

If underscores or whitespace in the input need to be rejected, then the string should first be validated, perhaps using fn:matches.

If other characters may legitimately appear in the input, for example a leading 0x, then this must first be removed by pre-processing the input.

If the input uses a different family of digits, then the value should first be converted to the required digits using fn:translate.

A string in the lexical space of xs:hexBinary will always be an acceptable input, provided it is not too long. So, for example, the expression "1DE=" => xs:base64Binary() => xs:hexBinary() => xs:string() => parse-integer(16) can be used to convert the Base 64 value 1DE= to the integer 54321, via the hexadecimal string D431.

Examples

Expression:	`parse-integer(" 200 ")`
Result:	200
Expression:	`parse-integer("-20")`
Result:	-20
Expression:	`parse-integer(" +100")`
Result:	100
Expression:	`parse-integer("ff", 16)`
Result:	255
Expression:	`parse-integer("FFFF FFFF", 16)`
Result:	4294967295
Expression:	`parse-integer("-FFFF_FFFF", 16)`
Result:	-4294967295
Expression:	`parse-integer("377", 8)`
Result:	255
Expression:	`parse-integer("101", 2)`
Result:	5
Expression:	`parse-integer("vv", 32)`
Result:	1023
Alphabetic base-26 numbering systems (hexavigesimal) can be parsed via translation. Note, enumerating systems that do not assign a symbol to zero (e.g., spreadsheet columns) must be preprocessed in a different fashion.
Expression:	lower-case("AAB") => translate("abcdefghijklmnopqrstuvwxyz", "0123456789abcdefghijklmnop") => parse-integer(26)
Result:	1
Digit-based numeration systems comparable to the Arabic numbers 0 through 9 can be parsed via translation.
Expression:	translate('٢٠٢٣', '٠١٢٣٤٥٦٧٨٩', '0123456789') => parse-integer()
Result:	2023

4.6 Formatting integers

Function	Meaning
`fn:format-integer`	Formats an integer according to a given picture string, using the conventions of a given natural language if specified.

4.6.1 fn:format-integer

Summary

Formats an integer according to a given picture string, using the conventions of a given natural language if specified.

Signature

`fn:format-integer`(
`$value`	`as` `xs:integer?`,
`$picture`	`as` `xs:string`,
`$language`	`as` `xs:string?`	`:=` `()`
) `as` `xs:string`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on default language.

The three-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is an empty sequence, the function returns a zero-length string.

In all other cases, the $picture argument describes the format in which $value is output.

The rules that follow describe how non-negative numbers are output. If the value of $value is negative, the rules below are applied to the absolute value of $value, and a minus sign is prepended to the result.

The value of $picture consists of the following, in order:

An optional radix, which is an integer in the range 2 to 36, written using ASCII digits (0-9) without any leading zero;
A circumflex (^), which is present if the radix is present, and absent otherwise.

A circumflex is recognized as marking the presence of a radix only if (a) it is immediately preceded by an integer in the range 2 to 36, and (b) it is followed (somewhere within the primary format token) by an "X" or "x". In other cases, the circumflex is treated as a grouping separator. For example, the picture 9^000 outputs the number 2345 as "2^345", whereas 9^XXX outputs "3185". This rule is to ensure backwards compatibility.
A primary format token. This is always present and must not be zero-length.
An optional format modifier.

If the string contains one or more semicolons then the last semicolon is taken as terminating the primary format token, and everything that follows is taken as the format modifier; if the string contains no semicolon then the format modifier is taken to be absent (which is equivalent to supplying a zero-length string).

If a radix is present, then the primary format token must follow the rules for a digit-pattern.

The primary format token is classified as one of the following:

A digit-pattern made up of optional-digit-signs, mandatory-digit-signs, and grouping-separator-signs.
- The optional-digit-sign is the character #.
- If the radix is absent, then a mandatory-digit-sign is a ·character· in Unicode category Nd. All mandatory-digit-signs within the format token must be from the same digit family, where a digit family is a sequence of ten consecutive characters in Unicode category Nd, having digit values 0 through 9. Within the format token, these digits are interchangeable: a three-digit number may thus be indicated equivalently by 000, 001, or 999.
  
  If the primary format token contains at least one Unicode digit, then the primary format token is taken as a decimal digit pattern, and in this case it must match the regular expression ^((\p{Nd}|#|[^\p{N}\p{L}])+?)$. If it contains a digit but does not match this pattern, a dynamic error is raised [err:FODF1310].
- If the radix (call it R) is present (including the case where an explicit radix of 10 is used), then the character used as the mandatory-digit-sign is either "x" or "X". If any mandatory-digit-sign is upper-case "X", then all mandatory-digit-signs must be upper-case "X". The digit family used in the output comprises the first R characters of the alphabet 0123456789abcdefghijklmnopqrstuvwxyz, but using upper-case letters in place of lower-case if an upper-case "X" is used as the mandatory-digit-sign.
  
  In this case the primary format token must match the regular expression ^(([Xx#]|[^\p{N}\p{L}])+?)$
- a grouping-separator-sign is a non-alphanumeric character, that is a ·character· whose Unicode category is other than Nd, Nl, No, Lu, Ll, Lt, Lm or Lo.
Note:

If a semicolon is to be used as a grouping separator, then the primary format token as a whole must be followed by another semicolon, to ensure that the grouping separator is not mistaken as a separator between the primary format token and the format modifier.

There must be at least one mandatory-digit-sign. There may be zero or more optional-digit-signs, and (if present) these must precede all mandatory-digit-signs. There may be zero or more grouping-separator-signs. A grouping-separator-sign must not appear at the start or end of the digit-pattern, nor adjacent to another grouping-separator-sign.

The corresponding output is a number in the specified radix, using this digit family, with at least as many digits as there are mandatory-digit-signs in the format token. Thus:
- A format token 1 generates the sequence 0 1 2 ... 10 11 12 ...
- A format token 01 (or equivalently, 00 or 99) generates the sequence 00 01 02 ... 09 10 11 12 ... 99 100 101
- A format token of ١ (Arabic-Indic digit one) generates the sequence ١ then ٢ then ٣ ...
- A format token of 16^xx generates the sequence 00 01 02 03 ... 08 09 0a 0b 0c 0d 0e 0f 10 11 ...
- A format token of 16^X generates the sequence 0 1 2 3 ... 8 9 A B C D E F 10 11 ...
The grouping-separator-signs are handled as follows:
1. The position of grouping separators within the format token, counting backwards from the last digit, indicates the position of grouping separators to appear within the formatted number, and the character used as the grouping-separator-sign within the format token indicates the character to be used as the corresponding grouping separator in the formatted number.
2. More specifically, the position of a grouping separator is the number of optional-digit-signs and mandatory-digit-signs appearing between the grouping separator and the right-hand end of the primary format token.
3. Grouping separators are defined to be regular if the following conditions apply:
  1. There is at least one grouping separator.
  2. Every grouping separator is the same character (call it C).
  3. There is a positive integer G (the grouping size) such that:
    1. The position of every grouping separator is an integer multiple of G, and
    2. Every positive integer multiple of G that is less than the number of optional-digit-signs and mandatory-digit-signs in the primary format token is the position of a grouping separator.
4. The grouping separator template is a (possibly infinite) set of (position, character) pairs.
5. If grouping separators are regular, then the grouping separator template contains one pair of the form (n×G, C) for every positive integer n where G is the grouping size and C is the grouping character.
6. Otherwise (when grouping separators are not regular), the grouping separator template contains one pair of the form (P, C) for every grouping separator found in the primary formatting token, where C is the grouping separator character and P is its position.
7. Note:
  
  If there are no grouping separators, then the grouping separator template is an empty set.
The number is formatted as follows:
1. Let S₁ be the result of formatting the supplied number in the appropriate radix: for radix 10 this will be the value obtained by casting it to xs:string.
2. Let S₂ be the result of padding S₁ on the left with as many leading zeroes as are needed to ensure that it contains at least as many digits as the number of mandatory-digit-signs in the primary format token.
3. Let S₃ be the result of replacing all decimal digits (0-9) in S₂ with the corresponding digits from the selected digit family. (This has no effect when the selected digit family uses ASCII digits (0-9), which will always be the case if a radix is specified.)
4. Let S₄ be the result of inserting grouping separators into S₃: for every (position P, character C) pair in the grouping separator template where P is less than the number of digits in S₃, insert character C into S₃ at position P, counting from the right-hand end.
5. Let S₅ be the result of converting S₄ into ordinal form, if an ordinal modifier is present, as described below.
6. The result of the function is then S₅.
The format token A, which generates the sequence A B C ... Z AA AB AC....
The format token a, which generates the sequence a b c ... z aa ab ac....
The format token i, which generates the sequence i ii iii iv v vi vii viii ix x ....
The format token I, which generates the sequence I II III IV V VI VII VIII IX X ....
The format token w, which generates numbers written as lower-case words, for example in English, one two three four ...
The format token W, which generates numbers written as upper-case words, for example in English, ONE TWO THREE FOUR ...
The format token Ww, which generates numbers written as title-case words, for example in English, One Two Three Four ...
Any other format token, which indicates a numbering sequence in which that token represents the number 1 (one) (but see the note below). It is ·implementation-defined· which numbering sequences, additional to those listed above, are supported. If an implementation does not support a numbering sequence represented by the given token, it must use a format token of 1.

Note:

In some traditional numbering sequences additional signs are added to denote that the letters should be interpreted as numbers, for example, in ancient Greek the dexia keraia (x0374, ʹ) and sometimes the aristeri keraia (x0375, ͵). These should not be included in the format token.

For all format tokens other than a digit-pattern, there may be ·implementation-defined· lower and upper bounds on the range of numbers that can be formatted using this format token; indeed, for some numbering sequences there may be intrinsic limits. For example, the format token ① (circled digit one, ①) has a range imposed by the Unicode character repertoire — zero to 20 in Unicode versions prior to 3.2, or zero to 50 in subsequent versions. For the numbering sequences described above any upper bound imposed by the implementation must not be less than 1000 (one thousand) and any lower bound must not be greater than 1. Numbers that fall outside this range must be formatted using the format token 1.

The above expansions of numbering sequences for format tokens such as a and i are indicative but not prescriptive. There are various conventions in use for how alphabetic sequences continue when the alphabet is exhausted, and differing conventions for how roman numerals are written (for example, IV versus IIII as the representation of the number 4). Sometimes alphabetic sequences are used that omit letters such as i and o. This specification does not prescribe the detail of any sequence other than those sequences consisting entirely of decimal digits.

Many numbering sequences are language-sensitive. This applies especially to the sequence selected by the tokens w, W and Ww. It also applies to other sequences, for example different languages using the Cyrillic alphabet use different sequences of characters, each starting with the letter #x410 (Cyrillic capital letter A). In such cases, the $language argument specifies which language conventions are to be used. If the argument is specified, the value should be either an empty sequence or a value that would be valid for the xml:lang attribute (see [Extensible Markup Language (XML) 1.0 (Fifth Edition)]). Note that this permits the identification of sublanguages based on country codes (from ISO 3166-1) as well as identification of dialects and regions within a country.

The set of languages for which numbering is supported is ·implementation-defined·. If the $language argument is absent, or is set to an empty sequence, or is invalid, or is not a language supported by the implementation, then the number is formatted using the default language from the dynamic context.

The format modifier must be a string that matches the regular expression ^([co]($.+$)?)?[at]?$. That is, if it is present it must consist of one or more of the following, in order:

either c or o, optionally followed by a sequence of characters enclosed between parentheses, to indicate cardinal or ordinal numbering respectively, the default being cardinal numbering
either a or t, to indicate alphabetic or traditional numbering respectively, the default being ·implementation-defined·.

If the o modifier is present, this indicates a request to output ordinal numbers rather than cardinal numbers. For example, in English, when used with the format token 1, this outputs the sequence 1st 2nd 3rd 4th ..., and when used with the format token w outputs the sequence first second third fourth ....

The string of characters between the parentheses, if present, is used to select between other possible variations of cardinal or ordinal numbering sequences. The interpretation of this string is ·implementation-defined·. No error occurs if the implementation does not define any interpretation for the defined string.

It is ·implementation-defined· what combinations of values of the format token, the language, and the cardinal/ordinal modifier are supported. If ordinal numbering is not supported for the combination of the format token, the language, and the string appearing in parentheses, the request is ignored and cardinal numbers are generated instead.

The use of the a or t modifier disambiguates between numbering sequences that use letters. In many languages there are two commonly used numbering sequences that use letters. One numbering sequence assigns numeric values to letters in alphabetic sequence, and the other assigns numeric values to each letter in some other manner traditional in that language. In English, these would correspond to the numbering sequences specified by the format tokens a and i. In some languages, the first member of each sequence is the same, and so the format token alone would be ambiguous. In the absence of the a or t modifier, the default is ·implementation-defined·.

Error Conditions

A dynamic error is raised [err:FODF1310] if the format token is invalid, that is, if it violates any mandatory rules (indicated by an emphasized must or required keyword in the above rules). For example, the error is raised if the primary format token contains a digit but does not match the required regular expression.

Notes

Note the careful distinction between conditions that are errors and conditions where fallback occurs. The principle is that an error in the syntax of the format picture will be reported by all processors, while a construct that is recognized by some implementations but not others will never result in an error, but will instead cause a fallback representation of the integer to be used.
The following notes apply when a digit-pattern is used:
1. If grouping-separator-signs appear at regular intervals within the format token, then the sequence is extrapolated to the left, so grouping separators will be used in the formatted number at every multiple of N. For example, if the format token is 0'000 then the number one million will be formatted as 1'000'000, while the number fifteen will be formatted as 0'015.
2. The only purpose of optional-digit-signs is to mark the position of grouping-separator-signs. For example, if the format token is #'##0 then the number one million will be formatted as 1'000'000, while the number fifteen will be formatted as 15. A grouping separator is included in the formatted number only if there is a digit to its left, which will only be the case if either (a) the number is large enough to require that digit, or (b) the number of mandatory-digit-signs in the format token requires insignificant leading zeros to be present.
3. Grouping separators are not designed for effects such as formatting a US telephone number as (365)123-9876. In general they are not suitable for such purposes because (a) only single characters are allowed, and (b) they cannot appear at the beginning or end of the number.
4. Numbers will never be truncated. Given the digit-pattern 01, the number three hundred will be output as 300, despite the absence of any optional-digit-sign.
The following notes apply when ordinal numbering is selected using the o modifier.

In some languages, the form of numbers (especially ordinal numbers) varies depending on the grammatical context: they may have different genders and may decline with the noun that they qualify. In such cases the string appearing in parentheses after the letter c or o may be used to indicate the variation of the cardinal or ordinal number required.

The way in which the variation is indicated will depend on the conventions of the language.

For inflected languages that vary the ending of the word, the approach recommended in the previous version of this specification was to indicate the required ending, preceded by a hyphen: for example in German, appropriate values might be o(-e), o(-er), o(-es), o(-en).

Another approach, which might usefully be adopted by an implementation based on the open-source ICU localization library [ICU], or any other library making use of the Unicode Common Locale Data Repository [Unicode CLDR], is to allow the value in parentheses to be the name of a registered numbering rule set for the language in question, conventionally prefixed with a percent sign: for example, o(%spellout-ordinal-masculine), or c(%spellout-cardinal-year).
The following notes apply when the primary format token is neither a digit-pattern nor one of the seven other defined format tokens (A, a, i, I, w, W, Ww), but is an arbitrary token representing the number 1:

Unexpected results may occur for traditional numbering. For example, in an implementation that supports traditional numbering system in Greek, the example format-integer(19, "α;t") might return δπιιιι or ιθ, depending upon whether the ancient acrophonic or late antique alphabetic system is supported.

Unexpected results may also occur for alphabetic numbering. For example, in an implementation that supports alphabetic numbering system in Greek, someone writing format-integer(19, "α;a") might expect the nineteenth Greek letter, #x3C4 τ, but the implementation might return the eighteenth one, #x3C3 σ, because the latter is the nineteenth item in the sequence of lowercase Greek letters in Unicode (the sequence is interrupted because of the final form of the sigma, #x3C2 ς). Because Greek never had a final capital sigma, Unicode has marked #x3A2, the eighteenth codepoint in the sequence of Greek capital letters, as reserved, to ensure that every Greek uppercase letter is always 32 codepoints less than its lowercase counterpart. Therefore, someone writing format-integer(18, "Α;a") might expect the eighteenth Greek capital letter, #x3A3 Σ, but an implementation might return #x3a2, the eighteenth position in the sequence of Greek capital letters, but unassigned to any character.

Examples

Expression:	`format-integer(123, '0000')`
Result:	"0123"
`format-integer(123, 'w')` might return `"one hundred and twenty-three"`
Ordinal numbering in Italian: The specification `"1;o(-º)"` with `$language` equal to `it`, if supported, should produce the sequence:
1º 2º 3º 4º ...
The specification `"Ww;o"` with `$language` equal to `it`, if supported, should produce the sequence:
Primo Secondo Terzo Quarto Quinto ...
Expression:	`format-integer(21, '1;o', 'en')`
Result:	"21st"
`format-integer(14, 'Ww;o(-e)', 'de')` might return `"Vierzehnte"`
Expression:	`format-integer(7, 'a')`
Result:	"g"
Expression:	`format-integer(27, 'a')`
Result:	"aa"
Expression:	`format-integer(57, 'I')`
Result:	"LVII"
Expression:	`format-integer(1234, '#;##0;')`
Result:	"1;234"
Expression:	`format-integer(1234, '16^xxxx')`
Result:	"04d2"
Expression:	`format-integer(1234, '16^X')`
Result:	"4D2"
Expression:	`format-integer(12345678, '16^xxxx_xxxx')`
Result:	"00bc_614e"
Expression:	`format-integer(12345678, '16^#_xxxx')`
Result:	"bc_614e"
Expression:	`format-integer(255, '2^xxxx xxxx')`
Result:	"1111 1111"
Expression:	`format-integer(1023, '32^XXXX')`
Result:	"00VV"
Expression:	`format-integer(1023, '10^XXXX')`
Result:	"1023"
Expression:	`format-integer(1023, '10^00')`
Result:	"10^23"

4.7 Formatting numbers

This section defines a function for formatting decimal and floating point numbers.

Function	Meaning
`fn:format-number`	Returns a string containing a number formatted according to a given picture string, taking account of decimal formats specified in the static context.

Note:

This function can be used to format any numeric quantity, including an integer. For integers, however, the fn:format-integer function offers additional possibilities. Note also that the picture strings used by the two functions are not 100% compatible, though they share some options in common.

4.7.1 Defining a decimal format

Decimal formats are defined in the static context, and the way they are defined is therefore outside the scope of this specification. XSLT and XQuery both provide custom syntax for creating a decimal format.

The static context provides a set of decimal formats. One of the decimal formats is unnamed, the others (if any) are identified by a QName. There is always an unnamed decimal format available, but its contents are ·implementation-defined·.

Each decimal format provides a set of named properties, described in the following table:

Name	Type	Usage (non-normative)
`decimal-separator`	A single ·character·	Defines the character used to represent the decimal point (typically `.`) both in the picture string and in the formatted number.
`grouping-separator`	A single ·character·	Defines the character used to separate groups of digits (typically `,`) both in the picture string and in the formatted number.
`exponent-separator`	A single ·character·	Defines the character used to separate the mantissa from the exponent in scientific notation (typically `e`) both in the picture string and in the formatted number.
`infinity`	A ·string·	Defines the string used to represent the value positive or negative infinity in the formatted number (typically `Infinity`)
`minus-sign`	A single ·character·	Defines the character used as a minus sign in the formatted number if there is no subpicture for formatting negative numbers (typically `-`, x2D)
`NaN`	A ·string·	Defines the string used to represent the value `NaN` in the formatted number
`percent`	A single ·character·	Defines the character used as a percent sign (typically `%`) both in the picture string and in the formatted number
`per-mille`	A single ·character·	Defines the character used as a per-mille sign (typically `‰`, x2030) both in the picture string and in the formatted number
`zero-digit`	A single ·character·, which must be a character in Unicode category Nd with decimal digit value 0 (zero)	Defines the characters used in the picture string to represent a mandatory digit: for example, if the zero-digit is `0` then any of the digits `0` to `9` may be used (interchangeably) in the picture string to represent a mandatory digit, and in the formatted number the characters `0` to `9` will be used to represent the digits zero to nine.
`digit`	A single ·character·	Defines the character used in the picture string to represent an optional digit (typically `#`)
`pattern-separator`	A single ·character·	Defines the character used in the picture string to separate the positive and negative subpictures (typically `;`)

Note:

A phrase such as "The minus-sign^XP31 character" is to be read as “the character assigned to the minus-sign^XP31 property in the relevant decimal format within the static context”.

[Definition] The decimal digit family of a decimal format is the sequence of ten digits with consecutive Unicode ·codepoints· starting with the character that is the value of the zero-digit^XP31 property.

[Definition] The optional digit character is the character that is the value of the digit^XP31 property.

For any named or unnamed decimal format, the properties representing characters used in a ·picture string· must have distinct values. These properties are decimal-separator^XP31 , grouping-separator^XP31, exponent-separator^XP31, percent^XP31, per-mille^XP31, digit^XP31, and pattern-separator^XP31. Furthermore, none of these properties may be equal to any ·character· in the ·decimal digit family·.

4.7.2 fn:format-number

Summary

Returns a string containing a number formatted according to a given picture string, taking account of decimal formats specified in the static context.

Signature

`fn:format-number`(
`$value`	`as` `xs:numeric?`,
`$picture`	`as` `xs:string`,
`$decimal-format-name`	`as` `union(xs:string, xs:QName)?`	`:=` `()`
) `as` `xs:string`

Properties

The two-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

The three-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on decimal formats, and namespaces.

Rules

The effect of the two-argument form of the function is equivalent to calling the three-argument form with an empty sequence as the value of the third argument.

The function formats $value as a string using the ·picture string· specified by the $picture argument and the decimal-format named by the $decimal-format-name argument, or the unnamed decimal-format, if there is no $decimal-format-name argument. The syntax of the picture string is described in 4.7.3 Syntax of the picture string.

The $value argument may be of any numeric data type (xs:double, xs:float, xs:decimal, or their subtypes including xs:integer). Note that if an xs:decimal is supplied, it is not automatically promoted to an xs:double, as such promotion can involve a loss of precision.

If the supplied value of the $value argument is an empty sequence, the function behaves as if the supplied value were the xs:double value NaN.

The value of $decimal-format-name, if present and non-empty, must be either an xs:QName, or a string which after removal of leading and trailing whitespace is in the form of an EQName as defined in the XPath 4.0 grammar, that is one of the following:

A lexical QName, which is expanded using the statically known namespaces. The default namespace is not used (no prefix means no namespace).
A URIQualifiedName using the syntax Q{uri}local, where the URI can be zero-length to indicate a name in no namespace.

The decimal format that is used is the decimal format in the static context whose name matches $decimal-format-name if supplied, or the unnamed decimal format in the static context otherwise.

The evaluation of the fn:format-number function takes place in two phases, an analysis phase described in 4.7.4 Analyzing the picture string and a formatting phase described in 4.7.5 Formatting the number.

The analysis phase takes as its inputs the ·picture string· and the variables derived from the relevant decimal format in the static context, and produces as its output a number of variables with defined values. The formatting phase takes as its inputs the number to be formatted and the variables produced by the analysis phase, and produces as its output a string containing a formatted representation of the number.

The result of the function is the formatted string representation of the supplied number.

Error Conditions

A dynamic error is raised [err:FODF1280] if the $decimal-format-name argument is supplied as an xs:string that is neither a valid lexical QName nor a valid URIQualifiedName, or if it uses a prefix that is not found in the statically known namespaces, or if the static context does not contain a declaration of a decimal-format with a matching expanded QName. If the processor is able to detect the error statically (for example, when the argument is supplied as a string literal), then the processor may optionally signal this as a static error.

Notes

A string is an ordered sequence of characters, and this specification uses terms such as “left” and “right”, “preceding” and “following” in relation to this ordering, irrespective of the position of the characters when visually rendered on some output medium. Both in the picture string and in the result string, digits with higher significance (that is, representing higher powers of ten) always precede digits with lower significance, even when the rendered text flow is from right to left.

The type of the third argument changes in version 4.0 from xs:string to union(xs:string, xs:QName). This introduces a minor incompatibility: for example, it is no longer possible to supply a value of type xs:anyURI.

Examples

Expression	Result
The following examples assume a default decimal format in which the chosen digits are the ASCII digits 0-9, the decimal separator is `.`, the grouping separator is `,`, the minus-sign is `-`, and the percent-sign is `%`.
`format-number(12345.6, '#,###.00')`	"12,345.60"
`format-number(12345678.9, '9,999.99')`	"12,345,678.90"
`format-number(123.9, '9999')`	"0124"
`format-number(0.14, '01%')`	"14%"
`format-number(-6, '000')`	"-006"
The following example assumes the existence of a decimal format named `ch` in which the grouping separator is `ʹ` and the decimal separator is `·`:
format-number( 1234.5678, '#ʹ##0·00', 'ch' )	"1ʹ234·57"
The following examples assume that the exponent separator in decimal format `fortran` is `E`:
`format-number(1234.5678, '00.000E0', 'fortran')`	"12.346E2"
`format-number(0.234, '0.0E0', 'fortran')`	"2.3E-1"
`format-number(0.234, '#.00E0', 'fortran')`	"0.23E0"
`format-number(0.234, '.00E0', 'fortran')`	".23E0"

History

Changed in 4.0: The decimal format name can now be supplied as a value of type xs:QName, as an alternative to supplying a lexical QName as an instance of xs:string.

4.7.3 Syntax of the picture string

Note:

This differs from the format-number function previously defined in XSLT 2.0 in that any digit can be used in the picture string to represent a mandatory digit: for example the picture strings "000", "001", and "999" are equivalent. The digits will all be from the same decimal digit family, specifically, the sequence of ten consecutive digits starting with the digit assigned to the zero-digit property. This change is to align format-number (which previously used "000") with format-dateTime (which used 001).

[Definition] The formatting of a number is controlled by a picture string. The picture string is a sequence of ·characters·, in which the characters assigned to the properties decimal-separator^XP31 , exponent-separator^XP31, grouping-separator^XP31, digit^XP31, and pattern-separator^XP31 and the members of the ·decimal digit family·, are classified as active characters, and all other characters (including the values of the properties percent^XP31 and per-mille^XP31) are classified as passive characters.

A dynamic error is raised [err:FODF1310] if the ·picture string· does not conform to the following rules. Note that in these rules the words "preceded" and "followed" refer to characters anywhere in the string; they are not to be read as "immediately preceded" and "immediately followed".

A picture-string consists either of a sub-picture, or of two sub-pictures separated by the pattern-separator^XP31 character. A picture-string must not contain more than one instance of the pattern-separator^XP31 character. If the picture-string contains two sub-pictures, the first is used for positive and unsigned zero values and the second for negative values.
A sub-picture must not contain more than one instance of the decimal-separator^XP31 character.
A sub-picture must not contain more than one instance of the percent^XP31 or per-mille^XP31 characters, and it must not contain one of each.
The mantissa part of a sub-picture (defined below) must contain at least one character that is either an ·optional digit character· or a member of the ·decimal digit family·.
A sub-picture must not contain a passive character that is preceded by an active character and that is followed by another active character.
A sub-picture must not contain a grouping-separator^XP31 character that appears adjacent to a decimal-separator^XP31 character, or in the absence of a decimal-separator^XP31 character, at the end of the integer part.
A sub-picture must not contain two adjacent instances of the grouping-separator^XP31 character.
The integer part of a sub-picture (defined below) must not contain a member of the ·decimal digit family· that is followed by an instance of the ·optional digit character·. The fractional part of a sub-picture (defined below) must not contain an instance of the ·optional digit character· that is followed by a member of the ·decimal digit family·.
A character that matches the exponent-separator^XP31 property is treated as an exponent-separator-sign if it is both preceded and followed within the sub-picture by an active character. Otherwise, it is treated as a passive character. A sub-picture must not contain more than one character that is treated as an exponent-separator-sign.
A sub-picture that contains a percent^XP31 or per-mille^XP31 character must not contain a character treated as an exponent-separator-sign.
If a sub-picture contains a character treated as an exponent-separator-sign then this must be followed by one or more characters that are members of the ·decimal digit family·, and it must not be followed by any active character that is not a member of the ·decimal digit family·.

The mantissa part of the sub-picture is defined as the part that appears to the left of the exponent-separator-sign if there is one, or the entire sub-picture otherwise. The exponent part of the subpicture is defined as the part that appears to the right of the exponent-separator-sign; if there is no exponent-separator-sign then the exponent part is absent.

The integer part of the sub-picture is defined as the part that appears to the left of the decimal-separator^XP31 character if there is one, or the entire mantissa part otherwise.

The fractional part of the sub-picture is defined as that part of the mantissa part that appears to the right of the decimal-separator^XP31 character if there is one, or the part that appears to the right of the rightmost active character otherwise. The fractional part may be zero-length.

4.7.4 Analyzing the picture string

This phase of the algorithm analyzes the ·picture string· and the properties from the selected decimal format in the static context, and it has the effect of setting the values of various variables, which are used in the subsequent formatting phase. These variables are listed below. Each is shown with its initial setting and its datatype.

Several variables are associated with each sub-picture. If there are two sub-pictures, then these rules are applied to one sub-picture to obtain the values that apply to positive and unsigned zero numbers, and to the other to obtain the values that apply to negative numbers. If there is only one sub-picture, then the values for both cases are derived from this sub-picture.

The variables are as follows:

The integer-part-grouping-positions is a sequence of integers representing the positions of grouping separators within the integer part of the sub-picture. For each grouping-separator^XP31 character that appears within the integer part of the sub-picture, this sequence contains an integer that is equal to the total number of ·optional digit character· and ·decimal digit family· characters that appear within the integer part of the sub-picture and to the right of the grouping-separator^XP31 character.

The grouping is defined to be regular if the following conditions apply:
1. There is an least one grouping-separator in the integer part of the sub-picture.
2. There is a positive integer G (the grouping size) such that the position of every grouping-separator in the integer part of the sub-picture is a positive integer multiple of G.
3. Every position in the integer part of the sub-picture that is a positive integer multiple of G is occupied by a grouping-separator.
If the grouping is regular, then the integer-part-grouping-positions sequence contains all integer multiples of G as far as necessary to accommodate the largest possible number.
The minimum-integer-part-size is an integer indicating the minimum number of digits that will appear to the left of the decimal-separator character. It is initially set to the number of ·decimal digit family· characters found in the integer part of the sub-picture, but may be adjusted as described below.

Note:

There is no maximum integer part size. All significant digits in the integer part of the number will be displayed, even if this exceeds the number of ·optional digit character· and ·decimal digit family· characters in the subpicture.
The scaling factor is a non-negative integer used to determine the scaling of the mantissa in exponential notation. It is set to the number of ·decimal digit family· characters found in the integer part of the sub-picture.
The prefix is set to contain all passive characters in the sub-picture to the left of the leftmost active character. If the picture string contains only one sub-picture, the prefix for the negative sub-picture is set by concatenating the minus-sign^XP31 character and the prefix for the positive sub-picture (if any), in that order.
The fractional-part-grouping-positions is a sequence of integers representing the positions of grouping separators within the fractional part of the sub-picture. For each grouping-separator^XP31 character that appears within the fractional part of the sub-picture, this sequence contains an integer that is equal to the total number of ·optional digit character· and ·decimal digit family· characters that appear within the fractional part of the sub-picture and to the left of the grouping-separator^XP31 character.

Note:

There is no need to extrapolate grouping positions on the fractional side, because the number of digits in the output will never exceed the number of ·optional digit character· and ·decimal digit family· characters in the fractional part of the sub-picture.
The minimum-fractional-part-size is set to the number of ·decimal digit family· characters found in the fractional part of the sub-picture.
The maximum-fractional-part-size is set to the total number of ·optional digit character· and ·decimal digit family· characters found in the fractional part of the sub-picture.
If the effect of the above rules is that minimum-integer-part-size and maximum-fractional-part-size are both zero, then an adjustment is applied as follows:
- If an exponent separator is present then:
  - minimum-fractional-part-size is changed to 1 (one).
  - maximum-fractional-part-size is changed to 1 (one).
  Note:
  
  This has the effect that with the picture #.e9, the value 0.123 is formatted as 0.1e0
- Otherwise:
  - minimum-integer-part-size is changed to 1 (one).
  Note:
  
  This has the effect that with the picture #, the value 0.23 is formatted as 0
If all the following conditions are true:
- An exponent separator is present
- The minimum-integer-part-size is zero
- There is at least one ·optional digit character· in the integer part of the sub-picture
then the minimum-integer-part-size is changed to 1 (one).

Note:

This has the effect that with the picture .9e9, the value 0.1 is formatted as .1e0, while with the picture #.9e9, it is formatted as 0.1e0
If (after making the above adjustments) the minimum-integer-part-size and the minimum-fractional-part-size are both zero, then the minimum-fractional-part-size is set to 1 (one).
The minimum-exponent-size is set to the number of ·decimal digit family· characters found in the exponent part of the sub-picture if present, or zero otherwise.

Note:

The rules for the syntax of the picture string ensure that if an exponent separator is present, then the minimum-exponent-size will always be greater than zero.
The suffix is set to contain all passive characters to the right of the rightmost active character in the sub-picture.

Note:

If there is only one sub-picture, then all variables for positive numbers and negative numbers will be the same, except for prefix: the prefix for negative numbers will be preceded by the minus-sign^XP31 character.

4.7.5 Formatting the number

This section describes the second phase of processing of the fn:format-number function. This phase takes as input a number to be formatted (referred to as the input number), and the variables set up by analyzing the decimal format in the static context and the ·picture string·, as described above. The result of this phase is a string, which forms the return value of the fn:format-number function.

The algorithm for this second stage of processing is as follows:

If the input number is NaN (not a number), the result is the value of the pattern separator^XP31 property (with no prefix or suffix).
In the rules below, the positive sub-picture and its associated variables are used if the input number is positive, and the negative sub-picture and its associated variables are used if it is negative. For xs:double and xs:float, negative zero is taken as negative, positive zero as positive. For xs:decimal and xs:integer, the positive sub-picture is used for zero.
The adjusted number is determined as follows:
- If the sub-picture contains a percent^XP31 character, the adjusted number is the input number multiplied by 100.
- If the sub-picture contains a per-mille^XP31 character, the adjusted number is the input number multiplied by 1000.
- Otherwise, the adjusted number is the input number.
If the multiplication causes numeric overflow, no error occurs, and the adjusted number is positive or negative infinity as appropriate.
If the adjusted number is positive or negative infinity, the result is the concatenation of the appropriate prefix, the value of the infinity^XP31 property, and the appropriate suffix.
If the minimum exponent size is non-zero, and the adjusted number is non-zero, then the adjusted number is scaled to establish a mantissa and an integer exponent. The mantissa and exponent are chosen such that all the following conditions are true:
- The primitive type of the mantissa is the same as the primitive type of the adjusted number (integer, decimal, float, or double).
- The mantissa multiplied by ten to the power of the exponent is equal to the adjusted number.
- The mantissa (unless it is zero) is less than 10^N, and at least 10^N-1, where N is the scaling factor.
If the minimum exponent size is zero, then the mantissa is the adjusted number and there is no exponent.

If the minimum exponent size is non-zero and the adjusted number is zero, then the mantissa is the adjusted number and the exponent is zero.
The mantissa is converted (if necessary) to an xs:decimal value, using an implementation of xs:decimal that imposes no limits on the totalDigits or fractionDigits facets. If there are several such values that are numerically equal to the mantissa (bearing in mind that if the mantissa is an xs:double or xs:float, the comparison will be done by converting the decimal value back to an xs:double or xs:float), the one that is chosen should be one with the smallest possible number of digits not counting leading or trailing zeroes (whether significant or insignificant). For example, 1.0 is preferred to 0.9999999999, and 100000000 is preferred to 100000001. This value is then rounded so that it uses no more than maximum-fractional-part-size digits in its fractional part. The rounded number is defined to be the result of converting the mantissa to an xs:decimal value, as described above, and then calling the function fn:round-half-to-even with this converted number as the first argument and the maximum-fractional-part-size as the second argument, again with no limits on the totalDigits or fractionDigits in the result.
The absolute value of the rounded number is converted to a string in decimal notation, using the digits in the ·decimal digit family· to represent the ten decimal digits, and the decimal-separator^XP31 character to separate the integer part and the fractional part. This string must always contain a decimal-separator^XP31, and it must contain no leading zeroes and no trailing zeroes. The value zero will at this stage be represented by a decimal-separator^XP31 on its own.
If the number of digits to the left of the decimal-separator^XP31 character is less than minimum-integer-part-size, leading zero digit^XP31 characters are added to pad out to that size.
If the number of digits to the right of the decimal-separator^XP31 character is less than minimum-fractional-part-size, trailing zero digit^XP31 characters are added to pad out to that size.
For each integer N in the integer-part-grouping-positions list, a grouping-separator^XP31 character is inserted into the string immediately after that digit that appears in the integer part of the number and has N digits between it and the decimal-separator^XP31 character, if there is such a digit.
For each integer N in the fractional-part-grouping-positions list, a grouping-separator^XP31 character is inserted into the string immediately before that digit that appears in the fractional part of the number and has N digits between it and the decimal-separator^XP31 character, if there is such a digit.
If there is no decimal-separator^XP31 character in the sub-picture, or if there are no digits to the right of the decimal-separator character in the string, then the decimal-separator character is removed from the string (it will be the rightmost character in the string).
If an exponent exists, then the string produced from the mantissa as described above is extended with the following, in order: (a) the exponent-separator^XP31 character; (b) if the exponent is negative, the minus-sign^XP31 character; (c) the value of the exponent represented as a decimal integer, extended if necessary with leading zeroes to make it up to the minimum exponent size, using digits taken from the ·decimal digit family·.
The result of the function is the concatenation of the appropriate prefix, the string conversion of the number as obtained above, and the appropriate suffix.

4.8 Trigonometric and exponential functions

The functions in this section perform trigonometric and other mathematical calculations on xs:double values. They are provided primarily for use in applications performing geometrical computation, for example when generating SVG graphics.

Functions are provided to support the six most commonly used trigonometric calculations: sine, cosine and tangent, and their inverses arc sine, arc cosine, and arc tangent. Other functions such as secant, cosecant, and cotangent are not provided because they are easily computed in terms of these six.

The functions in this section (with the exception of math:pi) are specified by reference to [IEEE 754-2008], where they appear as Recommended operations in section 9. IEEE defines these functions for a variety of floating point formats; this specification defines them only for xs:double values. The IEEE specification applies with the following caveats:

IEEE states that the preferred quantum is language-defined. In this specification, it is ·implementation-defined·.
IEEE states that certain functions should raise the inexact exception if the result is inexact. In this specification, this exception if it occurs does not result in an error. Any diagnostic information is outside the scope of this specification.
IEEE defines various rounding algorithms for inexact results, and states that the choice of rounding direction, and the mechanisms for influencing this choice, are language-defined. In this specification, the rounding direction and any mechanisms for influencing it are ·implementation-defined·.
Certain operations (such as taking the square root of a negative number) are defined in IEEE to signal the invalid operation exception and return a quiet NaN. In this specification, such operations return NaN and do not raise an error. The same policy applies to operations (such as taking the logarithm of zero) that raise a divide-by-zero exception. Any diagnostic information is outside the scope of this specification.
Operations whose mathematical result is greater than the largest finite xs:double value are defined in IEEE to signal the overflow exception; operations whose mathematical result is closer to zero than the smallest non-zero xs:double value are similarly defined in IEEE to signal the underflow exception. The treatment of these exceptions in this specification is defined in 4.2 Arithmetic operators on numeric values.

Function	Meaning
`math:pi`	Returns an approximation to the mathematical constant π.
`math:exp`	Returns the value of `e`^x where `x` is the argument value.
`math:exp10`	Returns the value of `10`^x, where `x` is the supplied argument value.
`math:log`	Returns the natural logarithm of the argument.
`math:log10`	Returns the base-ten logarithm of the argument.
`math:pow`	Returns the result of raising the first argument to the power of the second.
`math:sqrt`	Returns the non-negative square root of the argument.
`math:sin`	Returns the sine of the argument. The argument is an angle in radians.
`math:cos`	Returns the cosine of the argument. The argument is an angle in radians.
`math:tan`	Returns the tangent of the argument. The argument is an angle in radians.
`math:asin`	Returns the arc sine of the argument.
`math:acos`	Returns the arc cosine of the argument.
`math:atan`	Returns the arc tangent of the argument.
`math:atan2`	Returns the angle in radians subtended at the origin by the point on a plane with coordinates (x, y) and the positive x-axis.

4.8.1 math:pi

Summary

Returns an approximation to the mathematical constant π.

Signature

math:pi() as xs:double

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

This function returns the xs:double value whose lexical representation is 3.141592653589793e0

Examples

Expression	Result
`2*math:pi()`	6.283185307179586e0
The expression `60 * (math:pi() div 180)` converts an angle of 60 degrees to radians.

4.8.2 math:exp

Summary

Returns the value of e^x where x is the argument value.

Signature

`math:exp`(
`$value`	`as` `xs:double?`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise the result is the mathematical constant e raised to the power of $value, as defined in the [IEEE 754-2008] specification of the exp function applied to 64-bit binary floating point values.

Notes

The treatment of overflow and underflow is defined in 4.2 Arithmetic operators on numeric values.

Examples

Expression	Result
`math:exp(())`	()
`math:exp(0)`	1.0e0
`math:exp(1)`	2.7182818284590455e0 (approximately)
`math:exp(2)`	7.38905609893065e0
`math:exp(-1)`	0.36787944117144233e0
`math:exp(math:pi())`	23.140692632779267e0
`math:exp(xs:double('NaN'))`	xs:double('NaN')
`math:exp(xs:double('INF'))`	xs:double('INF')
`math:exp(xs:double('-INF'))`	0.0e0

4.8.3 math:exp10

Summary

Returns the value of 10^x, where x is the supplied argument value.

Signature

`math:exp10`(
`$value`	`as` `xs:double?`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise the result is ten raised to the power of $value, as defined in the [IEEE 754-2008] specification of the exp10 function applied to 64-bit binary floating point values.

Notes

The treatment of overflow and underflow is defined in 4.2 Arithmetic operators on numeric values.

Examples

Expression	Result
`math:exp10(())`	()
`math:exp10(0)`	1.0e0
`math:exp10(1)`	1.0e1
`math:exp10(0.5)`	3.1622776601683795e0
`math:exp10(-1)`	1.0e-1
`math:exp10(xs:double('NaN'))`	xs:double('NaN')
`math:exp10(xs:double('INF'))`	xs:double('INF')
`math:exp10(xs:double('-INF'))`	0.0e0

4.8.4 math:log

Summary

Returns the natural logarithm of the argument.

Signature

`math:log`(
`$value`	`as` `xs:double?`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise the result is the natural logarithm of $value, as defined in the [IEEE 754-2008] specification of the log function applied to 64-bit binary floating point values.

Notes

The treatment of divideByZero and invalidOperation exceptions is defined in 4.2 Arithmetic operators on numeric values. The effect is that if the argument is zero, the result is -INF, and if it is negative, the result is NaN.

Examples

Expression	Result
`math:log(())`	()
`math:log(0)`	xs:double('-INF')
`math:log(math:exp(1))`	1.0e0
`math:log(1.0e-3)`	-6.907755278982137e0
`math:log(2)`	0.6931471805599453e0
`math:log(-1)`	xs:double('NaN')
`math:log(xs:double('NaN'))`	xs:double('NaN')
`math:log(xs:double('INF'))`	xs:double('INF')
`math:log(xs:double('-INF'))`	xs:double('NaN')

4.8.5 math:log10

Summary

Returns the base-ten logarithm of the argument.

Signature

`math:log10`(
`$value`	`as` `xs:double?`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise the result is the base-10 logarithm of $value, as defined in the [IEEE 754-2008] specification of the log10 function applied to 64-bit binary floating point values.

Notes

Examples

Expression	Result
`math:log10(())`	()
`math:log10(0)`	xs:double('-INF')
`math:log10(1.0e3)`	3.0e0
`math:log10(1.0e-3)`	-3.0e0
`math:log10(2)`	0.3010299956639812e0
`math:log10(-1)`	xs:double('NaN')
`math:log10(xs:double('NaN'))`	xs:double('NaN')
`math:log10(xs:double('INF'))`	xs:double('INF')
`math:log10(xs:double('-INF'))`	xs:double('NaN')

4.8.6 math:pow

Summary

Returns the result of raising the first argument to the power of the second.

Signature

`math:pow`(
`$x`	`as` `xs:double?`,
`$y`	`as` `xs:numeric`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $x is the empty sequence, the function returns the empty sequence.

If $y is an instance of xs:integer, the result is $x raised to the power of $y as defined in the [IEEE 754-2008] specification of the pown function applied to a 64-bit binary floating point value and an integer.

Otherwise $y is converted to an xs:double by numeric promotion, and the result is $x raised to the power of $y as defined in the [IEEE 754-2008] specification of the pow function applied to two 64-bit binary floating point values.

Notes

The treatment of the divideByZero and invalidOperation exceptions is defined in 4.2 Arithmetic operators on numeric values. Some of the consequences are illustrated in the examples below.

Examples

Expression	Result
`math:pow((), 93.7)`	()
`math:pow(2, 3)`	8.0e0
`math:pow(-2, 3)`	-8.0e0
`math:pow(2, -3)`	0.125e0
`math:pow(-2, -3)`	-0.125e0
`math:pow(2, 0)`	1.0e0
`math:pow(0, 0)`	1.0e0
`math:pow(xs:double('INF'), 0)`	1.0e0
`math:pow(xs:double('NaN'), 0)`	1.0e0
`math:pow(-math:pi(), 0)`	1.0e0
`math:pow(0e0, 3)`	0.0e0
`math:pow(0e0, 4)`	0.0e0
`math:pow(-0e0, 3)`	-0.0e0
`math:pow(0, 4)`	0.0e0
`math:pow(0e0, -3)`	xs:double('INF')
`math:pow(0e0, -4)`	xs:double('INF')
`math:pow(-0e0, -3)`	xs:double('-INF')
`math:pow(0, -4)`	xs:double('INF')
`math:pow(16, 0.5e0)`	4.0e0
`math:pow(16, 0.25e0)`	2.0e0
`math:pow(0e0, -3.0e0)`	xs:double('INF')
`math:pow(-0e0, -3.0e0)`	xs:double('-INF') (Odd-valued whole numbers are treated specially).
`math:pow(0e0, -3.1e0)`	xs:double('INF')
`math:pow(-0e0, -3.1e0)`	xs:double('INF')
`math:pow(0e0, 3.0e0)`	0.0e0
`math:pow(-0e0, 3.0e0)`	-0.0e0 (Odd-valued whole numbers are treated specially).
`math:pow(0e0, 3.1e0)`	0.0e0
`math:pow(-0e0, 3.1e0)`	0.0e0
`math:pow(-1, xs:double('INF'))`	1.0e0
`math:pow(-1, xs:double('-INF'))`	1.0e0
`math:pow(1, xs:double('INF'))`	1.0e0
`math:pow(1, xs:double('-INF'))`	1.0e0
`math:pow(1, xs:double('NaN'))`	1.0e0
`math:pow(-2.5e0, 2.0e0)`	6.25e0
`math:pow(-2.5e0, 2.00000001e0)`	xs:double('NaN')

4.8.7 math:sqrt

Summary

Returns the non-negative square root of the argument.

Signature

`math:sqrt`(
`$value`	`as` `xs:double?`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise the result is the mathematical non-negative square root of $value as defined in the [IEEE 754-2008] specification of the squareRoot function applied to 64-bit binary floating point values.

Notes

The treatment of the invalidOperation exception is defined in 4.2 Arithmetic operators on numeric values. The effect is that if the argument is less than zero, the result is NaN.

If $value is positive or negative zero, positive infinity, or NaN, then the result is $value. (Negative zero is the only case where the result can have negative sign)

Examples

Expression	Result
`math:sqrt(())`	()
`math:sqrt(0.0e0)`	0.0e0
`math:sqrt(-0.0e0)`	-0.0e0
`math:sqrt(1.0e6)`	1.0e3
`math:sqrt(2.0e0)`	1.4142135623730951e0
`math:sqrt(-2.0e0)`	xs:double('NaN')
`math:sqrt(xs:double('NaN'))`	xs:double('NaN')
`math:sqrt(xs:double('INF'))`	xs:double('INF')
`math:sqrt(xs:double('-INF'))`	xs:double('NaN')

4.8.8 math:sin

Summary

Returns the sine of the argument. The argument is an angle in radians.

Signature

`math:sin`(
`$radians`	`as` `xs:double?`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $radians is the empty sequence, the function returns the empty sequence.

Otherwise the result is the sine of $radians (which is treated as an angle in radians) as defined in the [IEEE 754-2008] specification of the sin function applied to 64-bit binary floating point values.

Notes

The treatment of the invalidOperation and underflow exceptions is defined in 4.2 Arithmetic operators on numeric values.

If $radians is positive or negative zero, the result is $radians.

If $radians is positive or negative infinity, or NaN, then the result is NaN.

Otherwise the result is always in the range -1.0e0 to +1.0e0

Examples

Expression	Result
`math:sin(())`	()
`math:sin(0)`	0.0e0
`math:sin(-0.0e0)`	-0.0e0
`math:sin(math:pi() div 2)`	1.0e0 (approximately)
`math:sin(-math:pi() div 2)`	-1.0e0 (approximately)
`math:sin(math:pi())`	0.0e0 (approximately)
`math:sin(xs:double('NaN'))`	xs:double('NaN')
`math:sin(xs:double('INF'))`	xs:double('NaN')
`math:sin(xs:double('-INF'))`	xs:double('NaN')

4.8.9 math:cos

Summary

Returns the cosine of the argument. The argument is an angle in radians.

Signature

`math:cos`(
`$radians`	`as` `xs:double?`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $radians is the empty sequence, the function returns the empty sequence.

If $radians is positive or negative infinity, or NaN, then the result is NaN.

Otherwise the result is the cosine of $radians (which is treated as an angle in radians) as defined in the [IEEE 754-2008] specification of the cos function applied to 64-bit binary floating point values.

Notes

The treatment of the invalidOperation exception is defined in 4.2 Arithmetic operators on numeric values.

If $radians is positive or negative zero, the result is $radians.

If $radiansis positive or negative infinity, or NaN, then the result is NaN.

Otherwise the result is always in the range -1.0e0 to +1.0e0

Examples

Expression	Result
`math:cos(())`	()
`math:cos(0)`	1.0e0
`math:cos(-0.0e0)`	1.0e0
`math:cos(math:pi() div 2)`	0.0e0 (approximately)
`math:cos(-math:pi() div 2)`	0.0e0 (approximately)
`math:cos(math:pi())`	-1.0e0 (approximately)
`math:cos(xs:double('NaN'))`	xs:double('NaN')
`math:cos(xs:double('INF'))`	xs:double('NaN')
`math:cos(xs:double('-INF'))`	xs:double('NaN')

4.8.10 math:tan

Summary

Returns the tangent of the argument. The argument is an angle in radians.

Signature

`math:tan`(
`$radians`	`as` `xs:double?`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $radians is the empty sequence, the function returns the empty sequence.

Otherwise the result is the tangent of $radians (which is treated as an angle in radians) as defined in the [IEEE 754-2008] specification of the tan function applied to 64-bit binary floating point values.

Notes

The treatment of the invalidOperation and underflow exceptions is defined in 4.2 Arithmetic operators on numeric values.

If $radians is positive or negative infinity, or NaN, then the result is NaN.

Examples

Expression	Result
`math:tan(())`	()
`math:tan(0)`	0.0e0
`math:tan(-0.0e0)`	-0.0e0
`math:tan(math:pi() div 4)`	1.0e0 (approximately)
`math:tan(-math:pi() div 4)`	-1.0e0 (approximately)
`1 div math:tan(math:pi() div 2)`	0.0e0 (approximately) (Mathematically, tan(π/2) is positive infinity. But because `math:pi() div 2` returns an approximation, the result of `math:tan(math:pi() div 2)` will be a large but finite number.)
`1 div math:tan(-math:pi() div 2)`	-0.0e0 (approximately) (Mathematically, tan(-π/2) is negative infinity. But because `-math:pi() div 2` returns an approximation, the result of `math:tan(-math:pi() div 2)` will be a large but finite negative number.)
`math:tan(math:pi())`	0.0e0 (approximately)
`math:tan(xs:double('NaN'))`	xs:double('NaN')
`math:tan(xs:double('INF'))`	xs:double('NaN')
`math:tan(xs:double('-INF'))`	xs:double('NaN')

4.8.11 math:asin

Summary

Returns the arc sine of the argument.

Signature

`math:asin`(
`$value`	`as` `xs:double?`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise the result is the arc sine of $value as defined in the [IEEE 754-2008] specification of the asin function applied to 64-bit binary floating point values. The result is in the range -π/2 to +π/2 radians.

Notes

The treatment of the invalidOperation and underflow exceptions is defined in 4.2 Arithmetic operators on numeric values.

If $value is positive or negative zero, the result is $value.

If $value is NaN, or if its absolute value is greater than one, then the result is NaN.

In other cases the result is an xs:double value representing an angle θ in radians in the range -π/2 <=θ <= +π/2.

Examples

Expression	Result
`math:asin(())`	()
`math:asin(0)`	0.0e0
`math:asin(-0.0e0)`	-0.0e0
`math:asin(1.0e0)`	1.5707963267948966e0 (approximately)
`math:asin(-1.0e0)`	-1.5707963267948966e0 (approximately)
`math:asin(2.0e0)`	xs:double('NaN')
`math:asin(xs:double('NaN'))`	xs:double('NaN')
`math:asin(xs:double('INF'))`	xs:double('NaN')
`math:asin(xs:double('-INF'))`	xs:double('NaN')

4.8.12 math:acos

Summary

Returns the arc cosine of the argument.

Signature

`math:acos`(
`$value`	`as` `xs:double?`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise the result is the arc cosine of $value, as defined in the [IEEE 754-2008] specification of the acos function applied to 64-bit binary floating point values. The result is in the range zero to +π radians.

Notes

The treatment of the invalidOperation exception is defined in 4.2 Arithmetic operators on numeric values.

If $value is NaN, or if its absolute value is greater than one, then the result is NaN.

In other cases the result is an xs:double value representing an angle θ in radians in the range 0 <= θ<= +π.

Examples

Expression	Result
`math:acos(())`	()
`math:acos(0)`	1.5707963267948966e0 (approximately)
`math:acos(-0.0e0)`	1.5707963267948966e0 (approximately)
`math:acos(1.0e0)`	0.0e0
`math:acos(-1.0e0)`	3.141592653589793e0 (approximately)
`math:acos(2.0e0)`	xs:double('NaN')
`math:acos(xs:double('NaN'))`	xs:double('NaN')
`math:acos(xs:double('INF'))`	xs:double('NaN')
`math:acos(xs:double('-INF'))`	xs:double('NaN')

4.8.13 math:atan

Summary

Returns the arc tangent of the argument.

Signature

`math:atan`(
`$value`	`as` `xs:double?`
) `as` `xs:double?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise the result is the arc tangent of $value, as defined in the [IEEE 754-2008] specification of the atan function applied to 64-bit binary floating point values. The result is in the range -π/2 to +π/2 radians.

Notes

The treatment of the underflow exception is defined in 4.2 Arithmetic operators on numeric values.

If $value is positive or negative zero, the result is $value.

If $value is NaN then the result is NaN.

In other cases the result is an xs:double value representing an angle θ in radians in the range -π/2 <=θ <= +π/2.

Examples

Expression	Result
`math:atan(())`	()
`math:atan(0)`	0.0e0
`math:atan(-0.0e0)`	-0.0e0
`math:atan(1.0e0)`	0.7853981633974483e0 (approximately)
`math:atan(-1.0e0)`	-0.7853981633974483e0 (approximately)
`math:atan(xs:double('NaN'))`	xs:double('NaN')
`math:atan(xs:double('INF'))`	1.5707963267948966e0 (approximately)
`math:atan(xs:double('-INF'))`	-1.5707963267948966e0 (approximately)

4.8.14 math:atan2

Summary

Returns the angle in radians subtended at the origin by the point on a plane with coordinates (x, y) and the positive x-axis.

Signature

`math:atan2`(
`$y`	`as` `xs:double`,
`$x`	`as` `xs:double`
) `as` `xs:double`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The result is the value of atan2(y, x) as defined in the [IEEE 754-2008] specification of the atan2 function applied to 64-bit binary floating point values. The result is in the range -π to +π radians.

Notes

The treatment of the underflow exception is defined in 4.2 Arithmetic operators on numeric values. The following rules apply when the values are finite and non-zero, (subject to rules for overflow, underflow and approximation).

If either argument is NaN then the result is NaN.

If $x is positive, then the value of atan2($y, $x) is atan($y div $x).

If $x is negative, then:

If $y is positive, then the value of atan2($y, $x) is atan($y div $x) + π.
If $y is negative, then the value of atan2($y, $x) is atan($y div $x) - π.

Some results for special values of the arguments are shown in the examples below.

Examples

Expression	Result
`math:atan2(+0.0e0, 0.0e0)`	0.0e0
`math:atan2(-0.0e0, 0.0e0)`	-0.0e0
`math:atan2(+0.0e0, -0.0e0)`	3.141592653589793e0
`math:atan2(-0.0e0, -0.0e0)`	-3.141592653589793e0
`math:atan2(-1, 0.0e0)`	-1.5707963267948966e0
`math:atan2(+1, 0.0e0)`	1.5707963267948966e0
`math:atan2(-0.0e0, -1)`	-3.141592653589793e0
`math:atan2(+0.0e0, -1)`	3.141592653589793e0
`math:atan2(-0.0e0, +1)`	-0.0e0
`math:atan2(+0.0e0, +1)`	+0.0e0

4.9 Random Numbers

Function	Meaning
`fn:random-number-generator`	Returns a random number generator, which can be used to generate sequences of random numbers.

4.9.1 fn:random-number-generator

Summary

Returns a random number generator, which can be used to generate sequences of random numbers.

Signature

`fn:random-number-generator`(
`$seed`	`as` `xs:anyAtomicType?`	`:=` `()`
) `as` `random-number-generator-record`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns a random number generator. A random number generator is represented as a value of type random-number-generator-record, defined as follows:

`random-number-generator-record`:
`record(`
`number`	`as` `xs:double`,
`next`	`as` `function() as random-number-generator-record`,
`permute`	`as` `function(item()) as item()`,
`*`
`)`

That is, the result of the function is a map containing three entries. The keys of each entry are strings:

The entry with key "number" holds a random number; it is an xs:double greater than or equal to zero (0.0e0), and less than one (1.0e0).
The entry with key "next" is a zero-arity function that can be called to return another random number generator.

The properties of this function are as follows:
- name: absent
- parameter names: ()
- signature: () => map(xs:string, item())
- non-local variable bindings: none
- implementation: implementation-dependent
The entry with key "permute" is a function with arity 1 (one), which takes an arbitrary sequence as its argument, and returns a random permutation of that sequence.

The properties of this function are as follows:
- name: absent
- parameter names: "arg"
- signature: (item()*) => item()*
- non-local variable bindings: none
- implementation: implementation-dependent

Calling the fn:random-number-generator function with no arguments is equivalent to calling the single-argument form of the function with an implementation-dependent seed.

Calling the fn:random-number-generator function with an empty sequence as $seed is equivalent to calling the single-argument form of the function with an implementation-dependent seed.

If a $seed is supplied, it may be an atomic value of any type.

Both forms of the function are ·deterministic·: calling the function twice with the same arguments, within a single ·execution scope·, produces the same results.

The value of the number entry should be such that all eligible xs:double values are equally likely to be chosen the distribution of numbers is uniform: for example, the probability of the number being in the range 0.1e0 to 0.2e0 is the same as the probability of its being in the range 0.8e0 to 0.9e0.

The function returned in the permute entry should be such that all permutations of the supplied sequence are equally likely to be chosen.

The map returned by the fn:random-number-generator function may contain additional entries beyond those specified here, but it must match the record type defined above. The meaning of any additional entries is ·implementation-defined·. To avoid conflict with any future version of this specification, the keys of any such entries should start with an underscore character.

Notes

It is not meaningful to ask whether the functions returned in the next and permute functions resulting from two separate calls with the same seed are “the same function”, but the functions must be equivalent in the sense that calling them produces the same sequence of random numbers.

The repeatability of the results of function calls in different execution scopes is outside the scope of this specification. It is recommended that when the same seed is provided explicitly, the same random number sequence should be delivered even in different execution scopes; while if no seed is provided, the processor should choose a seed that is likely to be different from one execution scope to another. (The same effect can be achieved explicitly by using fn:current-dateTime() as a seed.)

The specification does not place strong conformance requirements on the actual randomness of the result; this is left to the implementation. It is desirable, for example, when generating a sequence of random numbers that the sequence should not get into a repeating loop; but the specification does not attempt to dictate this.

Examples

The following example returns a random permutation of the integers in the range `1` to `100`:
`fn:random-number-generator()?permute(1 to 100)`
The following example returns a 10% sample of the items in an input sequence `$seq`, chosen at random:
`fn:random-number-generator()?permute($seq)[position() = 1 to (count($seq) idiv 10)]`
The following XQuery code defines a function that can be called to produce a random sequence of `xs:double` values in the range zero to one, of specified length:
declare %public function r:random-sequence($length as xs:integer) as xs:double* { r:random-sequence($length, random-number-generator()) }; declare %private function r:random-sequence( $length as xs:integer, $record as record(number as xs:double, next as function(), ) ) { if ($length eq 0) then () else ($record?number, r:random-sequence($length - 1, $record?next())) }; r:random-sequence(200);

5 Functions on strings

This section specifies functions and operators on the [XML Schema Part 2: Datatypes Second Edition] xs:string datatype and the datatypes derived from it.

5.1 String types

The operators described in this section are defined on the following types.

- string
  - normalizedString
    - token
      - language
      - NMTOKEN
      - Name
        
        NCName
        
        ENTITY
        
        ID
        
        IDREF

Legend:

Supertype
- subtype

Built-in atomic types

They also apply to user-defined types derived by restriction from the above types.

5.2 Functions to assemble and disassemble strings

Function	Meaning
`fn:codepoints-to-string`	Returns an `xs:string` whose characters have supplied ·codepoints·.
`fn:string-to-codepoints`	Returns the sequence of ·codepoints· that constitute an `xs:string` value.

5.2.1 fn:codepoints-to-string

Summary

Returns an xs:string whose characters have supplied ·codepoints·.

Signature

`fn:codepoints-to-string`(
`$values`	`as` `xs:integer*`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the string made up from the ·characters· whose Unicode ·codepoints· are supplied in $values. This will be the zero-length string if $values is the empty sequence.

Error Conditions

A dynamic error is raised [err:FOCH0001] if any of the codepoints in $values is not a ·permitted character·.

Examples

Expression	Result
`codepoints-to-string((66, 65, 67, 72))`	"BACH"
`codepoints-to-string((2309, 2358, 2378, 2325))`	"अशॊक"
`codepoints-to-string(())`	""
`codepoints-to-string(0)`	Raises error FOCH0001.

5.2.2 fn:string-to-codepoints

Summary

Returns the sequence of ·codepoints· that constitute an xs:string value.

Signature

`fn:string-to-codepoints`(
`$value`	`as` `xs:string?`
) `as` `xs:integer*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns a sequence of integers, each integer being the Unicode ·codepoint· of the corresponding ·character· in $value.

If $value is a zero-length string or the empty sequence, the function returns the empty sequence.

Examples

Expression	Result
`string-to-codepoints("Thérèse")`	(84, 104, 233, 114, 232, 115, 101)

5.3 Comparison of strings

Function	Meaning
`fn:codepoint-equal`	Returns `true` if two strings are equal, considered codepoint-by-codepoint.
`fn:collation-key`	Given a string value and a collation, generates an internal value called a collation key, with the property that the matching and ordering of collation keys reflects the matching and ordering of strings under the specified collation.
`fn:contains-token`	Determines whether or not any of the supplied strings, when tokenized at whitespace boundaries, contains the supplied token, under the rules of the supplied collation.

5.3.1 Collations

A collation is a specification of the manner in which ·strings· are compared and, by extension, ordered. When values whose type is xs:string or a type derived from xs:string are compared (or, equivalently, sorted), the comparisons are inherently performed according to some collation (even if that collation is defined entirely on codepoint values). The [Character Model for the World Wide Web 1.0: Fundamentals] observes that some applications may require different comparison and ordering behaviors than other applications. Similarly, some users having particular linguistic expectations may require different behaviors than other users. Consequently, the collation must be taken into account when comparing strings in any context. Several functions in this and the following section make use of a collation.

Collations can indicate that two different codepoints are, in fact, equal for comparison purposes (e.g., “v” and “w” are considered equivalent in some Swedish collations). Strings can be compared codepoint-by-codepoint or in a linguistically appropriate manner, as defined by the collation.

Some collations, especially those based on the Unicode Collation Algorithm (see [UTS #10]) can be “tailored” for various purposes. This document does not discuss such tailoring, nor does it provide a mechanism to perform tailoring. Instead, it assumes that the collation argument to the various functions below is a tailored and named collation.

The ·Unicode codepoint collation· is a collation available in every implementation, which sorts based on codepoint values. For further details see 5.3.2 The Unicode Codepoint Collation.

Collations may or may not perform Unicode normalization on strings before comparing them.

This specification assumes that collations are named and that the collation name may be provided as an argument to string functions. Functions that allow specification of a collation do so with an argument whose type is xs:string but whose lexical form must conform to an xs:anyURI. This specification also defines the manner in which a default collation is determined if the collation argument is not specified in calls of functions that use a collation but allow it to be omitted.

If the collation is specified using a relative URI reference, it is resolved relative to an ·implementation-defined· base URI.

Note:

Previous versions of this specification stated that it must be resolved against the Static Base URI^XP40, but this is not always operationally convenient. It is recommended that processors should provide a means of setting the base URI for resolving collation URIs independently of the Static Base URI^XP40, though for backwards compatibility, the Static Base URI^XP40 or Executable Base URI^XP40 should be used as a default.

This specification does not define whether or not the collation URI is dereferenced. The collation URI may be an abstract identifier, or it may refer to an actual resource describing the collation. If it refers to a resource, this specification does not define the nature of that resource. One possible candidate is that the resource is a locale description expressed using the Locale Data Markup Language: see [UTS #35].

Functions such as fn:compare and fn:max that compare xs:string values use a single collation URI to identify all aspects of the collation rules. This means that any parameters such as the strength of the collation must be specified as part of the collation URI. For example, suppose there is a collation http://www.example.com/collations/French that refers to a French collation that compares on the basis of base characters. Collations that use the same basic rules, but with higher strengths, for example, base characters and accents, or base characters, accents and case, would need to be given different names, say http://www.example.com/collations/French1 and http://www.example.com/collations/French2. Note that some specifications use the term collation to refer to an algorithm that can be parameterized, but in this specification, each possible parameterization is considered to be a distinct collation.

The XQuery/XPath static context includes a provision for a default collation that can be used for string comparisons and ordering operations. See the description of the static context in Section 2.1.1 Static Context ^XP31. If the default collation is not specified by the user or the system, the default collation is the ·Unicode codepoint collation·.

Note:

XML allows elements to specify the xml:lang attribute to indicate the language associated with the content of such an element. This specification does not use xml:lang to identify the default collation because using xml:lang does not produce desired effects when the two strings to be compared have different xml:lang values or when a string is multilingual.

5.3.2 The Unicode Codepoint Collation

[Definition] The collation URI http://www.w3.org/2005/xpath-functions/collation/codepoint identifies a collation which must be recognized by every implementation: it is referred to as the Unicode codepoint collation (not to be confused with the Unicode collation algorithm).

The Unicode codepoint collation does not perform any normalization on the supplied strings.

The collation is defined as follows. Each of the two strings is converted to a sequence of integers using the fn:string-to-codepoints function. These two sequences $A and $B are then compared as follows:

If both sequences are empty, the strings are equal.
If one sequence is empty and the other is not, then the string corresponding to the empty sequence is less than the other string.
If the first integer in $A is less than the first integer in $B, then the string corresponding to $A is less than the string corresponding to $B.
If the first integer in $A is greater than the first integer in $B, then the string corresponding to $A is greater than the string corresponding to $B.
Otherwise (the first pair of integers are equal), the result is obtained by applying the same rules recursively to fn:tail($A) and fn:tail($B)

Note:

While the Unicode codepoint collation does not produce results suitable for quality publishing of printed indexes or directories, it is adequate for many purposes where a restricted alphabet is used, such as sorting of vehicle registrations.

5.3.3 The Unicode Collation Algorithm

This specification defines a family of collation URIs representing tailorings of the Unicode Collation Algorithm (UCA) as defined in [UTS #10]. The parameters used for tailoring the UCA are based on the parameters defined in the Locale Data Markup Language (LDML), defined in [UTS #35].

This family of URIs use the scheme and path http://www.w3.org/2013/collation/UCA followed by an optional query part. The query part, if present, consists of a question mark followed by a sequence of zero or more semicolon-separated parameters. Each parameter is a keyword-value pair, the keyword and value being separated by an equals sign.

All implementations must recognize URIs in this family in the collation argument of functions that take a collation argument.

If the fallback parameter is present with the value no, then the implementation must either use a collation that conforms with the rules in the Unicode specifications for the requested tailoring, or fail with a static or dynamic error indicating that it does not provide the collation (the error code should be the same as if the collation URI were not recognized). If the fallback parameter is omitted or takes the value yes, and if the collation URI is well-formed according to the rules in this section, then the implementation must accept the collation URI, and should use the available collation that most closely reflects the user’s intentions. For example, if the collation URI requested is http://www.w3.org/2013/collation/UCA?lang=se;fallback=yes and the implementation does not include a fully conformant version of the UCA tailored for Swedish, then it may choose to use a Swedish collation that is known to differ from the UCA definition, or one whose conformance has not been established. It might even, as a last resort, fall back to using codepoint collation.

If two query parameters use the same keyword then the last one wins. If a query parameter uses a keyword or value which is not defined in this specification then the meaning is ·implementation-defined·. If the implementation recognizes the meaning of the keyword and value then it should interpret it accordingly; if it does not recognize the keyword or value then if the fallback parameter is present with the value no it should reject the collation as unsupported, otherwise it should ignore the unrecognized parameter.

The following query parameters are defined. If any parameter is absent, the default is ·implementation-defined· except where otherwise stated. The meaning given for each parameter is non-normative; the normative specification is found in [UTS #35].

Keyword	Values	Meaning
fallback	yes \| no (default yes)	Determines whether the processor uses a fallback collation if a conformant collation is not available.
lang	language code: a string in the lexical space of `xs:language`.	The language whose collation conventions are to be used.
version	string	The version number of the UCA to be used.
strength	primary \| secondary \| tertiary \| quaternary \| identical, or 1\|2\|3\|4\|5 as synonyms (default tertiary / 3)	The collation strength as defined in UCA. Primary strength takes only the base form of the character into account (so A=a=Ä=ä); secondary strength ignores case but considers accents and diacritics as significant (so A=a and Ä=ä but ä≠a); tertiary considers case as significant (A≠a≠Ä≠ä); quaternary strength always considers as significant spaces and punctuation (data-base≠database; if `maxVariable` is `punct` or higher and `alternate` is not `non-ignorable`, lower strengths will treat data-base=database).
maxVariable	space \| punct \| symbol \| currency (default punct)	Given the sequence `space`, `punct`, `symbol`, `currency`, all characters in the specified group and earlier groups are treated as “noise” characters to be handled as defined by the `alternate` parameter. For example, `maxVariable=punct` indicates that characters classified as whitespace or punctuation get this treatment.
alternate	non-ignorable \| shifted \| blanked (default non-ignorable)	Controls the handling of characters such as spaces and hyphens; specifically, the "noise" characters in the groups selected by the `maxVariable` parameter. The value `non-ignorable` indicates that such characters are treated as distinct at the primary level (so `data base` sorts before `database`); `shifted` indicates that they are used to differentiate two strings only at the `quaternary` level, and `blanked` indicates that they are taken into account only at the `identical` level.
backwards	yes \| no (default no)	The value `backwards=yes` indicates that the last accent in the string is the most significant.
normalization	yes \| no (default no)	Indicates whether strings are converted to normalization form D.
caseLevel	yes \| no (default no)	When used with primary strength, setting `caseLevel=yes` has the effect of ignoring accents while taking account of case.
caseFirst	upper \| lower (default lower)	Indicates whether upper-case precedes lower-case or vice versa.
numeric	yes \| no (default no)	When `numeric=yes` is specified, a sequence of consecutive digits is interpreted as a number, for example `chap2` sorts before `chap12`.
reorder	a comma-separated sequence of reorder codes, where a reorder code is one of `space`, `punct`, `symbol`, `currency`, `digit`, or a four-letter script code defined in [ISO 15924 Register], the register of scripts maintained by the Unicode Consortium in its capacity as registration authority for [ISO 15924].	Determines the relative ordering of text in different scripts; for example the value `digit,Grek,Latn` indicates that digits precede Greek letters, which precede Latin letters.

Note:

This list excludes parameters that are inconvenient to express in a URI, or that are applicable only to substring matching.

5.3.4 The HTML ASCII Case-Insensitive Collation

The collation URI http://www.w3.org/2005/xpath-functions/collation/html-ascii-case-insensitive must be recognized by every implementation. It is designed to be compatible with the HTML ASCII case-insensitive collation as defined in [HTML: Living Standard] (section 4.6, Strings), which is used, for example, when matching HTML class attribute values.

The collation is defined as follows:

Let $HACI be the collation URI "http://www.w3.org/2005/xpath-functions/collation/html-ascii-case-insensitive".
Let $UCC be the Unicode Codepoint Collation URI http://www.w3.org/2005/xpath-functions/collation/codepoint.
Let $lc be the function fn:translate(?, "ABCDEFGHIJKLMNOPQRSTUVWXYZ", "abcdefghijklmnopqrstuvwxyz").
Then for any two strings $A and $B, the result of the comparison fn:compare($A, $B, $HACI) is defined to be the same as the result of fn:compare($lc($A), $lc($B), $UCC).

Note:

HTML5 defines the semantics of equality matching using this collation; this specification additionally defines ordering rules. The collation supports collation units and can therefore be used with functions such as fn:contains; each Unicode codepoint is a single collation unit.

The corresponding HTML5 definition is: A string A is an ASCII case-insensitive match for a string B, if the ASCII lowercase of A is the ASCII lowercase of B.

5.3.5 Choosing a collation

Many functions have a signature that includes a $collation argument, which is generally optional and takes default-collation() as its default value.

The collation to use for these functions is determined by the following rules:

If the function specifies an explicit collation, CollationA (e.g., if the optional collation argument is specified in a call of the fn:compare function), then:
- If CollationA is supported by the implementation, then CollationA is used.
- Otherwise, a dynamic error is raised [err:FOCH0002].
If no collation is explicitly specified for the function (that is, if the $collation argument is omitted or is set to an empty sequence), and the default collation in the XQuery/XPath static context is CollationB, then:
- If CollationB is supported by the implementation, then CollationB is used.
- Otherwise, a dynamic error is raised [err:FOCH0002].

Note:

Because the set of collations that are supported is ·implementation-defined·, an implementation has the option to support all collation URIs, in which case it will never raise this error.

If the value of the collation argument is a relative URI reference, it is resolved against the base-URI from the static context. If it is a relative URI reference and cannot be resolved, perhaps because the base-URI property in the static context is absent, a dynamic error is raised [err:FOCH0002].

Note:

There is no explicit requirement that the string used as a collation URI be a valid URI. Implementations will in many cases reject such strings on the grounds that do not identify a supported collation; they may also cause an error if they cannot be resolved against the relevant base URI.

5.3.6 fn:codepoint-equal

Summary

Returns true if two strings are equal, considered codepoint-by-codepoint.

Signature

`fn:codepoint-equal`(
`$value1`	`as` `xs:string?`,
`$value2`	`as` `xs:string?`
) `as` `xs:boolean?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If either argument is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns true or false depending on whether $value1 is equal to $value2, according to the Unicode codepoint collation (http://www.w3.org/2005/xpath-functions/collation/codepoint).

Notes

This function allows xs:anyURI values to be compared without having to specify the Unicode codepoint collation.

Examples

Expression	Result
`codepoint-equal("abcd", "abcd")`	true()
`codepoint-equal("abcd", "abcd ")`	false()
`codepoint-equal("", "")`	true()
`codepoint-equal("", ())`	()
`codepoint-equal((), ())`	()

5.3.7 fn:collation-key

Summary

Given a string value and a collation, generates an internal value called a collation key, with the property that the matching and ordering of collation keys reflects the matching and ordering of strings under the specified collation.

Signature

`fn:collation-key`(
`$value`	`as` `xs:string`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:base64Binary`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

Rules

Calling the one-argument version of this function is equivalent to calling the two-argument version supplying the default collation as the second argument.

The function returns an ·implementation-dependent· value with the property that, for any two strings $K1 and $K2:

collation-key($K1, $C) eq collation-key($K2, $C) if and only if compare($K1, $K2, $C) eq 0
collation-key($K1, $C) lt collation-key($K2, $C) if and only if compare($K1, $K2, $C) lt 0

The collation used by this function is determined according to the rules in 5.3.5 Choosing a collation. Collation keys are defined as xs:base64Binary values to ensure unambiguous and context-free comparison semantics.

An implementation is free to generate a collation key in any convenient way provided that it always generates the same collation key for two strings that are equal under the collation, and different collation keys for strings that are not equal. This holds only within a single ·execution scope·; an implementation is under no obligation to generate the same collation keys during a subsequent unrelated query or transformation.

It is possible to define collations that do not have the ability to generate collation keys. Supplying such a collation will cause the function to fail. The ability to generate collation keys is an ·implementation-defined· property of the collation.

Error Conditions

An error is raised [err:FOCH0004] if the specified collation does not support the generation of collation keys.

Notes

The function is provided primarily for use with maps. If a map is required where codepoint equality is inappropriate for comparing keys, then a common technique is to normalize the key so that equality matching becomes feasible. There are many ways keys can be normalized, for example by use of functions such as fn:upper-case, fn:lower-case, fn:normalize-space, or fn:normalize-unicode, but this function provides a way of normalizing them according to the rules of a specified collation. For example, if the collation ignores accents, then the function will generate the same collation key for two input strings that differ only in their use of accents.

The result of the function is defined to be an xs:base64Binary value. Binary values are chosen because they have unambiguous and context-free comparison semantics, because the value space is unbounded, and because the ordering rules are such that between any two values in the ordered value space, an arbitrary number of further values can be interpolated. The choice between xs:base64Binary and xs:hexBinary is arbitrary; the only operation that behaves differently between the two binary data types is conversion to/from a string, and this operation is not one that is normally required for effective use of collation keys.

For collations based on the Unicode Collation Algorithm, an algorithm for computing collation keys is provided in [UTS #10]. Implementations are not required to use this algorithm.

The fact that collation keys are ordered can be exploited in XQuery, whose order by clause does not allow the collation to be selected dynamically. This restriction can be circumvented by rewriting the clause order by $e/@key collation "URI" as order by fn:collation-key($e/@key, $collation), where $collation allows the collation to be chosen dynamically.

Note that xs:base64Binary becomes an ordered type in XPath 3.1, making binary collation keys possible.

Examples

Variables
let $C := 'http://www.w3.org/2013/collation/UCA?strength=primary'

Expression:	map:merge( (map { collation-key("A", $C): 1 }, map { collation-key("a", $C): 2 }), map { "duplicates": "use-last" } )(collation-key("A", $C))
Result:	2 (Given that the keys of the two entries are equal under the rules of the chosen collation, only one of the entries can appear in the result; the one that is chosen is the one from the last map in the input sequence.)
Expression:	let $M := map { collation-key("A", $C): 1, collation-key("B", $C): 2 } return $M(collation-key("a", $C))
Result:	1 (The strings `"A"` and `"a"` have the same collation key under this collation.)
As the above examples illustrate, it is important that when the `collation-key` function is used to add entries to a map, then it must also be used when retrieving entries from the map. This process can be made less error-prone by encapsulating the map within a function: `function($k) {$M(collation-key($k, $collation)}`.

5.3.8 fn:contains-token

Summary

Determines whether or not any of the supplied strings, when tokenized at whitespace boundaries, contains the supplied token, under the rules of the supplied collation.

Signature

`fn:contains-token`(
`$value`	`as` `xs:string*`,
`$token`	`as` `xs:string`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:boolean`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

The three-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI.

Rules

If $value is the empty sequence, the function returns false.

Leading and trailing whitespace is trimmed from $token. If the trimmed value of $token is a zero-length string, the function returns false.

The collation used by this function is determined according to the rules in 5.3.5 Choosing a collation.

The function returns true if and only if there is string in $value which, after tokenizing at whitespace boundaries, contains a token that is equal to the trimmed value of $token under the rules of the selected collation.

More formally, the function returns the value of the expression:

some $t in $input ! tokenize(.) satisfies 
  compare($t, replace($token, '^\s*|\s*$', ''), $collation) eq 0)

Notes

Interior whitespace within $token will cause the function to return false, unless such whitespace is ignored by the selected collation.

This function can be used for processing space-separated attribute values (for example, the XHTML and DITA class attribute), where one often needs to test for the presence of a single token in a space-separated list. The function is designed to work both when the attribute has been validated against an XSD list type, and when it appears as a single untyped string. It differs from the HTML 5 definition in that HTML 5 recognizes form feed (x0C) as a separator. To reproduce the HTML token matching behavior, the HTML ASCII case-insensitive collation should be used: see 5.3.4 The HTML ASCII Case-Insensitive Collation.

Examples

Expression:	`contains-token("red green blue ", "red")`
Result:	true()
Expression:	`contains-token(("red", "green", "blue"), " red ")`
Result:	true()
Expression:	`contains-token("red, green, blue", "red")`
Result:	false()
Expression:	contains-token( "red green blue", "RED", "http://www.w3.org/2005/xpath-functions/collation/html-ascii-case-insensitive" )
Result:	true()

5.4 Functions on string values

The following functions are defined on values of type xs:string and types derived from it.

Function	Meaning
`fn:char`	Returns a string containing a particular character or glyph.
`fn:characters`	Splits the supplied string into a sequence of single-character strings.
`fn:concat`	Returns the concatenation of the string values of the arguments.
`fn:string-join`	Returns a string created by concatenating the items in a sequence, with a defined separator between adjacent items.
`fn:substring`	Returns the part of `$value` beginning at the position indicated by `$start` and continuing for the number of ·characters· indicated by `$length`.
`fn:string-length`	Returns the number of ·characters· in a string.
`fn:normalize-space`	Returns `$value` with leading and trailing whitespace removed, and sequences of internal whitespace reduced to a single space character.
`fn:normalize-unicode`	Returns `$value` after applying Unicode normalization.
`fn:upper-case`	Converts a string to upper case.
`fn:lower-case`	Converts a string to lower case.
`fn:translate`	Returns `$value` modified by replacing or removing individual characters.
`fn:hash`	Returns a string representation of the results from a specified hash, checksum, or cyclic redundancy check function upon the input.

Notes:

When the above operators and functions are applied to datatypes derived from xs:string, they are guaranteed to return values that are instances of xs:string, but the value might or might not be an instance of the particular subtype of xs:string to which they were applied.

The strings returned by fn:concat and fn:string-join are not guaranteed to be normalized. But see note in fn:concat.

5.4.1 fn:char

Summary

Returns a string containing a particular character or glyph.

Signature

`fn:char`(
`$value`	`as` `union(xs:string, xs:positiveInteger)`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns a string, generally containing a single ·character· or glyph, identified by $value.

The supplied value of $value must be one of the following:

A Unicode codepoint, supplied as an integer. For example fn:char(9) returns the tab character.
An HTML5 character reference name (often referred to as an entity name) as defined at https://html.spec.whatwg.org/multipage/named-characters.html. The name is written with no leading ampersand and no trailing semicolon. For example fn:char("pi") represents the character π (x3C0) and fn:char("nbsp") returns the non-breaking space character, xA0.

A processor may recognize additional character reference names defined in other versions of HTML. Character reference names are case-sensitive.

In the event that the HTML5 character reference name identifies a string comprising multiple codepoints, that string is returned.

[TODO: add a proper bibliographic reference.]
A backslash-escape sequence from the set \n (newline, x0A), \r (carriage return, x0D), or \t (tab, x09).

The result must consist of ·permitted characters·. For example fn:char(0xDEAD) is invalid because it is in the surrogate range.

Error Conditions

The function fails with a dynamic error [err:FOCH0005] if $value is not a valid representation of a ·permitted character· or sequence of permitted characters.

Notes

Although all Unicode characters can appear in string literals (the delimiting quotation marks can be escaped by doubling them), some characters are not visually distinctive, so representing them by name may make code more readable. In addition, there may be contexts where it is necessary or prudent to write XPath expressions using ASCII characters only, for example where an expression is used in the query part of a URI.

A few HTML5 character reference names identify glyphs whose Unicode representation uses multiple codepoints. For example, the name NotEqualTilde refers to the glyph ≂̸ which is expressed using the two codepoints #x2242 #x0338. In such cases the string length of the result of the function will exceed one.

Examples

Expression	Result
`char("aacute")`	"á"
`char("eth")`	"ð"
`char(9)`	codepoints-to-string(9) (The character tab).
`char("\t")`	codepoints-to-string(9) (The character tab).
`char(0x20)`	" "
`char(0x1D1CA)`	"𝇊" (The character MUSICAL SYMBOL TEMPUS IMPERFECTUM CUM PROLATIONE PERFECTA).
`char("NotEqualTilde")`	codepoints-to-string((8770, 824)) (This HTML5 character reference name expands to multiple codepoints.)

History

Accepted for 4.0 on 2023-01-10; with actions on the editor for revision. See issue #121.

5.4.2 fn:characters

Summary

Splits the supplied string into a sequence of single-character strings.

Signature

`fn:characters`(
`$value`	`as` `xs:string?`
) `as` `xs:string*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns a sequence of strings, each string having length 1, containing the corresponding ·character· in $value.

If $value is a zero-length string or the empty sequence, the function returns the empty sequence.

More formally, the function returns the result of the expression fn:string-to-codepoints($value) ! fn:codepoints-to-string(.)

Examples

Expression	Result
`characters("Thérèse")`	("T", "h", "é", "r", "è", "s", "e")
`characters("")`	()
`characters(())`	()
`characters("Banana") => index-of("a")`	(2, 4, 6)
`characters("stretch") => string-join("-")`	"s-t-r-e-t-c-h"
"Banana" => characters() => reverse() => string-join()	"ananaB"

History

New in 4.0. Accepted 2022-09-20, subject to improving the description.

5.4.3 fn:concat

Summary

Returns the concatenation of the string values of the arguments.

Operator Mapping

The two-argument form of this function defines the semantics of the || operator.

Signature

`fn:concat`(
`$...`	`as` `xs:anyAtomicType*`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

This function accepts zero or more arguments, each declared with the required type xs:anyAtomicType*. The value $v supplied for each argument is first reduced to a single string as follows:

If XPath 1.0 compatibility mode is set to true in the static context of the function call, then the result of xs:string($v[1]).
Otherwise, the result of fn:string-join($v).

The resulting sequence of strings (one for each supplied argument) is then reduced to a single string by applying fn:string-join#1 to the sequence.

The fn:concat function is specified to allow zero or more arguments, which are concatenated together. This is the only function specified in this document that allows a variable number of arguments. This capability is retained for compatibility with [XML Path Language (XPath) Version 1.0].

Notes

As mentioned in 5.1 String types Unicode normalization is not automatically applied to the result of fn:concat. If a normalized result is required, fn:normalize-unicode can be applied to the xs:string returned by fn:concat. The following XQuery:

let $v1 := "I plan to go to Mu"
let $v2 := "?nchen in September"
return concat($v1, $v2)

where the ? represents either the actual Unicode character COMBINING DIARESIS (Unicode codepoint U+0308) or ̈, will return:

"I plan to go to Mu?nchen in September"

where the ? represents either the actual Unicode character COMBINING DIARESIS (Unicode codepoint U+0308) or ̈. It is worth noting that the returned value is not normalized in NFC; however, it is normalized in NFD.

However, the following XQuery:

let $v1 := "I plan to go to Mu"
let $v2 := "?nchen in September"
return normalize-unicode(concat($v1, $v2))

where ? represents either the actual Unicode character COMBINING DIARESIS (Unicode codepoint U+0308) or ̈, will return:

"I plan to go to München in September"

This returned result is normalized in NFC.

Examples

Expression:	`concat('un', 'grateful')`
Result:	"ungrateful"
Expression:	concat( 'Thy ', (), 'old ', "groans", "", ' ring', ' yet', ' in', ' my', ' ancient',' ears.' )
Result:	"Thy old groans ring yet in my ancient ears."
Expression:	`concat('Ciao!', ())`
Result:	"Ciao!"
Expression:	concat('Ingratitude, ', 'thou ', ('marble-hearted', ' fiend!'))
Result:	"Ingratitude, thou marble-hearted fiend!"
Expression:	`concat(01, 02, 03, 04, true())`
Result:	"1234true"
Expression:	`concat()`
Result:	""
Expression:	`10 \|\| '/' \|\| 6`
Result:	"10/6"

5.4.4 fn:string-join

Summary

Returns a string created by concatenating the items in a sequence, with a defined separator between adjacent items.

Signature

`fn:string-join`(
`$values`	`as` `xs:anyAtomicType*`,
`$separator`	`as` `xs:string?`	`:=` `""`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If the second argument is omitted or an empty sequence, the effect is the same as calling the two-argument version with $separator set to a zero-length string.

The function returns an xs:string created by casting each item in the sequence $values to an xs:string, and then concatenating the result strings in order, using the value of $separator as a separator between adjacent strings. If $separator is the zero-length string, then the items in $values are concatenated without a separator.

Notes

If $values is the empty sequence, the function returns the zero-length string.

Examples

Variables
let $doc := <doc> <chap> <section xml:id="xyz"/> </chap> </doc>

Expression:	`string-join(1 to 9)`
Result:	"123456789"
Expression:	`string-join(('Now', 'is', 'the', 'time', '...'), ' ')`
Result:	"Now is the time ..."
Expression:	string-join( ('Blow, ', 'blow, ', 'thou ', 'winter ', 'wind!'), '' )
Result:	"Blow, blow, thou winter wind!"
Expression:	`string-join((), 'separator')`
Result:	""
Expression:	`string-join(1 to 5, ', ')`
Result:	"1, 2, 3, 4, 5"
Expression:	$doc//@xml:id ! string-join((node-name(), '="', ., '"'))
Result:	'xml:id="xyz"'
Expression:	$doc//section ! string-join(ancestor-or-self::*/name(), '/')
Result:	"doc/chap/section"

5.4.5 fn:substring

Summary

Returns the part of $value beginning at the position indicated by $start and continuing for the number of ·characters· indicated by $length.

Signature

`fn:substring`(
`$value`	`as` `xs:string?`,
`$start`	`as` `xs:double`,
`$length`	`as` `xs:double?`	`:=` `()`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the zero-length string.

Otherwise, the function returns a string comprising those ·characters· of $value whose index position (counting from one) is greater than or equal to $start (rounded to an integer), and (if $length is specified and non-empty) less than the sum of $start and $length (both rounded to integers).

The characters returned do not extend beyond $value. If $start is zero or negative, only those characters in positions greater than zero are returned.

More specifically, the three argument version of the function returns the characters in $value whose position $p satisfies:

fn:round($start) <= $p and $p < fn:round($start) + fn:round($length)

The two argument version of the function assumes that $length is infinite and thus returns the ·characters· in $value whose position $p satisfies:

fn:round($start) <= $p

In the above computations, the rules for op:numeric-less-than and op:numeric-greater-than apply.

Notes

The first character of a string is located at position 1, not position 0.

The second and third arguments allow xs:double values (rather than requiring xs:integer) in order to achieve compatibility with XPath 1.0.

A surrogate pair counts as one character, not two.

The consequences of supplying values such as NaN or positive or negative infinity for the $start or $length arguments follow from the above rules, and are not always intuitive.

Examples

Expression	Result
`substring("motor car", 6)`	" car" (Characters starting at position 6 to the end of `$sourceString` are selected.)

`substring("metadata", 4, 3)`	"ada" (Characters at positions greater than or equal to 4 and less than 7 are selected.)
`substring("12345", 1.5, 2.6)`	"234" (Characters at positions greater than or equal to 2 and less than 5 are selected.)
`substring("12345", 0, 3)`	"12" (Characters at positions greater than or equal to 0 and less than 3 are selected. Since the first position is 1, these are the characters at positions 1 and 2.)
`substring("12345", 5, -3)`	"" (Characters at positions greater than or equal to 5 and less than 2 are selected.)
`substring("12345", -3, 5)`	"1" (Characters at positions greater than or equal to -3 and less than 2 are selected. Since the first position is 1, this is the character at position 1.)
`substring("12345", 0 div 0E0, 3)`	"" (Since `0 div 0E0` returns `NaN`, and `NaN` compared to any other number returns `false`, no characters are selected.)
`substring("12345", 1, 0 div 0E0)`	"" (As above.)
`substring((), 1, 3)`	""
`substring("12345", -42, 1 div 0E0)`	"12345" (Characters at positions greater than or equal to -42 and less than `INF` are selected.)
`substring("12345", -1 div 0E0, 1 div 0E0)`	"" (Since the value of `-INF + INF` is `NaN`, no characters are selected.)

History

Changed in 4.0: The third argument can now be supplied as an empty sequence.

5.4.6 fn:string-length

Summary

Returns the number of ·characters· in a string.

Signature

`fn:string-length`(
`$value`	`as` `xs:string?`	`:=` `fn:string(.)`
) `as` `xs:integer`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns an xs:integer equal to the length in ·characters· of $value.

Calling the zero-argument version of the function is equivalent to calling fn:string-length(fn:string(.)).

If $value is the empty sequence, the function returns the xs:integer value 0.

Error Conditions

If $value is not specified and the context value is absent^DM40, a type error is raised: [err:XPDY0002]^XP.

Notes

Unlike some programming languages, a ·codepoint· greater than 65535 counts as one character, not two.

There are situations where fn:string-length() has a different effect from fn:string-length(.). For example, if the context value is an attribute node typed as an xs:integer with the string value 000001, then fn:string-length() returns 6 (the length of the string value of the node), while fn:string-length(.) raises a type error (because the result of atomization is not an xs:string).

Examples

Expression:	string-length( "Harp not on that string, madam; that is past." )
Result:	45
Expression:	"ᾧ" => string-length()
Result:	1
Expression:	"ᾧ" => normalize-unicode("NFD") => string-length()
Result:	4 (For strings that consist of a base character with combining characters, each combining character is length 1.)
Expression:	`string-length(())`
Result:	0

5.4.7 fn:normalize-space

Summary

Returns $value with leading and trailing whitespace removed, and sequences of internal whitespace reduced to a single space character.

Signature

`fn:normalize-space`(
`$value`	`as` `xs:string?`	`:=` `fn:string(.)`
) `as` `xs:string`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the zero-length string.

The function returns a string constructed by stripping leading and trailing whitespace from $value, and replacing sequences of one or more adjacent whitespace characters with a single space, #x20.

The whitespace characters are defined in the metasymbol S (Production 3) of [Extensible Markup Language (XML) 1.0 (Fifth Edition)].

If no argument is supplied, then $value defaults to the string value (calculated using fn:string) of the context value (.).

Error Conditions

If no argument is supplied and the context value is absent^DM40, a type error is raised [err:XPDY0002]^XP.

Notes

The definition of whitespace is unchanged in [Extensible Markup Language (XML) 1.1 Recommendation]. It is repeated here for convenience:

S ::= (#x20 | #x9 | #xD | #xA)+

Examples

Expression:	normalize-space(" The wealthy curled darlings of our nation. ")
Result:	"The wealthy curled darlings of our nation."
Expression:	`normalize-space(())`
Result:	""

5.4.8 fn:normalize-unicode

Summary

Returns $value after applying Unicode normalization.

Signature

`fn:normalize-unicode`(
`$value`	`as` `xs:string?`,
`$form`	`as` `xs:string?`	`:=` `"NFC"`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the zero-length string.

If the second argument is omitted or an empty sequence, the result is the same as calling the two-argument version with $form set to the string "NFC".

Otherwise, the function returns $value normalized according to the rules of the normalization form identified by the value of $form.

The effective value of $form is the value of the expression fn:upper-case(fn:normalize-space($form)).

If the effective value of $form is “NFC”, then the function returns $value converted to Unicode Normalization Form C (NFC).
If the effective value of $form is “NFD”, then the function returns $value converted to Unicode Normalization Form D (NFD).
If the effective value of $form is “NFKC”, then the function returns $value in Unicode Normalization Form KC (NFKC).
If the effective value of $form is “NFKD”, then the function returns $value converted to Unicode Normalization Form KD (NFKD).
If the effective value of $form is “FULLY-NORMALIZED”, then the function returns $value converted to fully normalized form.
If the effective value of $form is the zero-length string, no normalization is performed and $value is returned.

Normalization forms NFC, NFD, NFKC, and NFKD, and the algorithms to be used for converting a string to each of these forms, are defined in [UAX #15].

The motivation for normalization form FULLY-NORMALIZED is explained in [Character Model for the World Wide Web 1.0: Normalization]. However, as that specification did not progress beyond working draft status, the normative specification is as follows:

A string is fully-normalized if (a) it is in normalization form NFC as defined in [UAX #15], and (b) it does not start with a composing character.
A composing character is a character that is one or both of the following:
- the second character in the canonical decomposition mapping of some character that is not listed in the Composition Exclusion Table defined in [UAX #15];
- of non-zero canonical combining class (as defined in [The Unicode Standard]).
A string is converted to FULLY-NORMALIZED form as follows:
- if the first character in the string is a composing character, prepend a single space (x20);
- convert the resulting string to normalization form NFC.

Conforming implementations must support normalization form NFC and may support normalization forms NFD, NFKC, NFKD, and FULLY-NORMALIZED. They may also support other normalization forms with ·implementation-defined· semantics.

It is ·implementation-defined· which version of Unicode (and therefore, of the normalization algorithms and their underlying data) is supported by the implementation. See [UAX #15] for details of the stability policy regarding changes to the normalization rules in future versions of Unicode. If the input string contains codepoints that are unassigned in the relevant version of Unicode, or for which no normalization rules are defined, the fn:normalize-unicode function leaves such codepoints unchanged. If the implementation supports the requested normalization form then it must be able to handle every input string without raising an error.

Error Conditions

A dynamic error is raised [err:FOCH0003] if the effective value of the $form argument is not one of the values supported by the implementation.

5.4.9 fn:upper-case

Summary

Converts a string to upper case.

Signature

`fn:upper-case`(
`$value`	`as` `xs:string?`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the zero-length string is returned.

Otherwise, the function returns $value after translating every ·character· to its upper-case correspondent as defined in the appropriate case mappings section in the Unicode standard [The Unicode Standard]. For versions of Unicode beginning with the 2.1.8 update, only locale-insensitive case mappings should be applied. Beginning with version 3.2.0 (and likely future versions) of Unicode, precise mappings are described in default case operations, which are full case mappings in the absence of tailoring for particular languages and environments. Every lower-case character that does not have an upper-case correspondent, as well as every upper-case character, is included in the returned value in its original form.

Notes

Case mappings may change the length of a string. In general, the fn:upper-case and fn:lower-case functions are not inverses of each other: fn:lower-case(fn:upper-case($s)) is not guaranteed to return $s, nor is fn:upper-case(fn:lower-case($s)). The Latin small letter dotless i (ı, U+0131, used in Turkish) is perhaps the most prominent lower-case letter which will not round-trip. The Latin capital letter i with dot above (İ, U+0130) is the most prominent upper-case letter which will not round trip; there are others, such as Latin capital letter sharp S (ẞ, U+1E9E), which was introduced in Unicode 5.1.

These functions may not always be linguistically appropriate (e.g. Turkish i without dot) or appropriate for the application (e.g. titlecase). In cases such as Turkish, a simple translation should be used first.

Because the function is not sensitive to locale, results will not always match user expectations. In Quebec, for example, the standard uppercase equivalent of è is È, while in metropolitan France it is more commonly E; only one of these is supported by the functions as defined.

Many characters of class Ll lack uppercase equivalents in the Unicode case mapping tables; many characters of class Lu lack lowercase equivalents.

Examples

Expression	Result
`upper-case("abCd0")`	"ABCD0"

5.4.10 fn:lower-case

Summary

Converts a string to lower case.

Signature

`fn:lower-case`(
`$value`	`as` `xs:string?`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If t$value is the empty sequence, the zero-length string is returned.

Otherwise, the function returns $value after translating every ·character· to its lower-case correspondent as defined in the appropriate case mappings section in the Unicode standard [The Unicode Standard]. For versions of Unicode beginning with the 2.1.8 update, only locale-insensitive case mappings should be applied. Beginning with version 3.2.0 (and likely future versions) of Unicode, precise mappings are described in default case operations, which are full case mappings in the absence of tailoring for particular languages and environments. Every upper-case character that does not have a lower-case correspondent, as well as every lower-case character, is included in the returned value in its original form.

Notes

Many characters of class Ll lack uppercase equivalents in the Unicode case mapping tables; many characters of class Lu lack lowercase equivalents.

Examples

Expression	Result
`lower-case("ABc!D")`	"abc!d"

5.4.11 fn:translate

Summary

Returns $value modified by replacing or removing individual characters.

Signature

`fn:translate`(
`$value`	`as` `xs:string?`,
`$replace`	`as` `xs:string`,
`$with`	`as` `xs:string`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the zero-length string.

Otherwise, the function returns a result string constructed by processing each ·character· in $value, in order, according to the following rules:

If the character does not appear in $replace then it is added to the result string unchanged.
If the character first appears in $replace at some position M, where the value of $with is M or more characters in length, then the character at position M in $with is added to the result string.
If the character first appears in $replace at some position M, where $with is less than M characters in length, then the character is omitted from the result string.

Notes

If $replace is the zero-length string then the function returns $value unchanged.

If a character occurs more than once in $replace, then the first occurrence determines the action taken.

If $with is longer than $replace, the excess characters are ignored.

Examples

Expression	Result
`translate("bar","abc","ABC")`	"BAr"
`translate("--aaa--","abc-","ABC")`	"AAA"
`translate("abcdabc", "abc", "AB")`	"ABdAB"

5.4.12 fn:hash

Summary

Returns a string representation of the results from a specified hash, checksum, or cyclic redundancy check function upon the input.

Signature

`fn:hash`(
`$value`	`as` `union(xs:string, xs:hexBinary, xs:base64Binary)?`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `xs:hexBinary?`

Properties

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

The two-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The $options argument, if present, defines additional parameters controlling how the process is conducted. The ·option parameter conventions· apply.

If the one-argument version of the function is used, the result is the same as calling the two-argument version, with the default $options settings.

If $value is the empty sequence, the function returns the empty sequence.

If $value is an instance of xs:string, it is converted to a sequence of octets on the basis of UTF-8 encoding. If $value is an instance of xs:base64Binary or xs:hexBinary, it is converted to a sequence of octets.

The function returns as xs:hexBinary the octets returned by passing $value as an octet sequence through the hash, checksum, or cyclical redundancy check function specified by the options map. The process is followed even if the input octet sequence is empty.

The entries that may appear in the $options map are as follows. The detailed rules for the interpretation of each option appear later.

Key Meaning

algorithm

Determines the algorithm to be used to calculate a checksum, hash, or cyclic redundancy check. The effective value is determined by first passing the value through fn:upper-case(fn:normalize-space()).

Conforming implementations must support the following options and the functions referred to by them:

MD5: the MD5 Message-Digest algorithm defined by [RFC 6151] (update to [RFC 1321]).
SHA-1: the SHA-1 algorithm, defined by [FIPS 180-4].
SHA-256: the SHA-256 algorithm, defined by [FIPS 180-4].

Conforming implementations may support other checksum and hash functions with implementation-defined semantics.

Type: xs:string
Default: MD5

Error Conditions

A dynamic error is raised ([TODO: error code]) if the effective value of the option algorithm is not one of the values supported by the implementation.

Notes

It is common for secure algorithms to be cryptographically broken, as has happened to the algorithms MD5 and SHA-1. Developers are responsible for ensuring that the algorithm chosen meets any expected security protocols, if relevant.

Additional security practices, such as salting, may be applied as a preprocessing step, or fn:hash() can be incorporated into more complex functions.

In most cases, the xs:hexBinary output of the function will be sought in string form. Because of serialization rules, casting to a string renders the hash in uppercase, and rendering in lowercase (as adopted by [RFC 1321] and [FIPS 180-4]) requires further adjustment.

Examples

Variables
let $doc := <doc>abc</doc>
let $salt := "D;%yL9TS:5PalS/d"

Expression	Result
`hash("abc") => string()`	"900150983CD24FB0D6963F7D28E17F72"
`hash("ABC") => string() => lower-case()`	"902fbdd2b1df0c4f70b4a5d23525e932"
`hash("") => string()`	"D41D8CD98F00B204E9800998ECF8427Eo"
`hash("ABC", map{"algorithm": "SHA-1"}) => string()`	"3C01BDBB26F358BAB27F267924AA2C9A03FCFDB8"
`hash("ABC", map{"algorithm": "sha-256")} => string()`	"B5D4045C3F466FA91FE2CC6ABE79232A1A57CDF104F7A26E716E0A1E2789DF78"
`hash($doc) => string()`	"900150983CD24FB0D6963F7D28E17F72"
`hash(serialize($doc), map{"algorithm": "sha-1"}) => xs:base64Binary() => string()`	"nJuRPrG2JU9HN86Ufv0W8W6Rb51u5cEQKiAC5I1MiL0="
`hash("password123" \|\| $salt, map{"algorithm": "SHA-256"}) => string()`	"9C9B913EB1B6254F4737CE947EFD16F16E916F9D6EE5C1102A2002E48D4C88BD"

History

New in 4.0.

5.5 Functions based on substring matching

The functions described in this section examine a string $arg1 to see whether it contains another string $arg2 as a substring. The result depends on whether $arg2 is a substring of $arg1, and if so, on the range of ·characters· in $arg1 which $arg2 matches.

When the ·Unicode codepoint collation· is used, this simply involves determining whether $arg1 contains a contiguous sequence of characters whose ·codepoints· are the same, one for one, with the codepoints of the characters in $arg2.

When a collation is specified, the rules are more complex.

All collations support the capability of deciding whether two ·strings· are considered equal, and if not, which of the strings should be regarded as preceding the other. For functions such as fn:compare, this is all that is required. For other functions, such as fn:contains, the collation needs to support an additional property: it must be able to decompose the string into a sequence of collation units, each unit consisting of one or more characters, such that two strings can be compared by pairwise comparison of these units. (“collation unit” is equivalent to "collation element" as defined in [UTS #10].) The string $arg1 is then considered to contain $arg2 as a substring if the sequence of collation units corresponding to $arg2 is a subsequence of the sequence of the collation units corresponding to $arg1. The characters in $arg1 that match are the characters corresponding to these collation units.

This rule may occasionally lead to surprises. For example, consider a collation that treats "Jaeger" and "Jäger" as equal. It might do this by treating "ä" as representing two collation units, in which case the expression fn:contains("Jäger", "eg") will return true. Alternatively, a collation might treat "ae" as a single collation unit, in which case the expression fn:contains("Jaeger", "eg") will return false. The results of these functions thus depend strongly on the properties of the collation that is used.

In addition, collations may specify that some collation units should be ignored during matching. If hyphen is an ignored collation unit, then fn:contains("code-point", "codepoint") will be true, and fn:contains("codepoint", "-") will also be true.

In the definitions below, we refer to the terms match and minimal match as defined in definitions DS2 and DS4 of [UTS #10]. In applying these definitions:

C is the collation; that is, the value of the $collation argument if specified, otherwise the default collation.
P is the (candidate) substring $arg2
Q is the (candidate) containing string $arg1
The boundary condition B is satisfied at the start and end of a string, and between any two characters that belong to different collation units (“collation elements” in the language of [UTS #10]). It is not satisfied between two characters that belong to the same collation unit.

It is possible to define collations that do not have the ability to decompose a string into units suitable for substring matching. An argument to a function defined in this section may be a URI that identifies a collation that is able to compare two strings, but that does not have the capability to split the string into collation units. Such a collation may cause the function to fail, or to give unexpected results, or it may be rejected as an unsuitable argument. The ability to decompose strings into collation units is an ·implementation-defined· property of the collation.

Function	Meaning
`fn:contains`	Returns `true` if the string `$value` contains `$substring` as a substring, taking collations into account.
`fn:starts-with`	Returns `true` if the string `$value` contains `$substring` as a leading substring, taking collations into account.
`fn:ends-with`	Returns `true` if the string `$value` contains `$substring` as a trailing substring, taking collations into account.
`fn:substring-before`	Returns the part of `$value` that precedes the first occurrence of `$substring`, taking collations into account.
`fn:substring-after`	Returns the part of `$value` that follows the first occurrence of `$substring`, taking collations into account.

5.5.1 fn:contains

Summary

Returns true if the string $value contains $substring as a substring, taking collations into account.

Signature

`fn:contains`(
`$value`	`as` `xs:string?`,
`$substring`	`as` `xs:string?`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:boolean`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

The three-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI.

Rules

If $value or $substring is the empty sequence, or contains only ignorable collation units, it is interpreted as the zero-length string.

If $substring is the zero-length string, then the function returns true.

If $value is the zero-length string, the function returns false.

The collation used by this function is determined according to the rules in 5.3.5 Choosing a collation.

The function returns an xs:boolean indicating whether or not $value contains (at the beginning, at the end, or anywhere within) at least one sequence of collation units that provides a minimal match to the collation units in $substring, according to the collation that is used.

Note:

Minimal match is defined in [UTS #10].

Error Conditions

A dynamic error may be raised [err:FOCH0004] if the specified collation does not support collation units.

Examples

Variables
let $coll := "http://www.w3.org/2013/collation/UCA?lang=en;alternate=blanked;strength=primary"

Expression	Result
The collation used in some of these examples, `$coll`, is a collation in which both `-` and `*` are ignorable collation units.
“Ignorable collation unit” is equivalent to “ignorable collation element” in [UTS #10].
`contains("tattoo", "t")`	true()
`contains("tattoo", "ttt")`	false()
`contains("", ())`	true() (The first rule is applied, followed by the second rule.)
contains( "abcdefghi", "-d-e-f-", $coll )	true()
contains( "abcdefghi*", "d-ef-", $coll )	true()
contains( "abcd**e---f--*ghi", "def", $coll )	true()
contains( (), "--**----", $coll )	true() (The second argument contains only ignorable collation units and is equivalent to the zero-length string.)

5.5.2 fn:starts-with

Summary

Returns true if the string $value contains $substring as a leading substring, taking collations into account.

Signature

`fn:starts-with`(
`$value`	`as` `xs:string?`,
`$substring`	`as` `xs:string?`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:boolean`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

The three-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI.

Rules

If $value or $substring is the empty sequence, or contains only ignorable collation units, it is interpreted as the zero-length string.

If $substring is the zero-length string, then the function returns true. If $value is the zero-length string and $substring is not the zero-length string, then the function returns false.

The collation used by this function is determined according to the rules in 5.3.5 Choosing a collation.

The function returns an xs:boolean indicating whether or not $value starts with a sequence of collation units that provides a match to the collation units of $substring according to the collation that is used.

Note:

Match is defined in [UTS #10].

Error Conditions

A dynamic error may be raised [err:FOCH0004] if the specified collation does not support collation units.

Examples

Variables
let $coll := "http://www.w3.org/2013/collation/UCA?lang=en;alternate=blanked;strength=primary"

Expression	Result
The collation used in some of these examples, `$coll`, is a collation in which both `-` and `*` are ignorable collation units.
“Ignorable collation unit” is equivalent to “ignorable collation element” in [UTS #10].
`starts-with("tattoo", "tat")`	true()
`starts-with("tattoo", "att")`	false()
`starts-with((), ())`	true()
starts-with( "abcdefghi", "-a-b-c-", $coll )	true()
starts-with( "abcdefghi*", "a-bc-", $coll )	true()
starts-with( "abcd**e---f--*ghi", "abcdef", $coll )	true()
starts-with( (), "--**----", $coll )	true() (The second argument contains only ignorable collation units and is equivalent to the zero-length string.)
starts-with( "-abcdefghi", "-abc", $coll )	true()

5.5.3 fn:ends-with

Summary

Returns true if the string $value contains $substring as a trailing substring, taking collations into account.

Signature

`fn:ends-with`(
`$value`	`as` `xs:string?`,
`$substring`	`as` `xs:string?`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:boolean`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

The three-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI.

Rules

If $value or $substring is the empty sequence, or contains only ignorable collation units, it is interpreted as the zero-length string.

If $substring is the zero-length string, then the function returns true. If $value is the zero-length string and the value of $substring is not the zero-length string, then the function returns false.

The collation used by this function is determined according to the rules in 5.3.5 Choosing a collation.

The function returns an xs:boolean indicating whether or not $value ends with a sequence of collation units that provides a match to the collation units of $substring according to the collation that is used.

Note:

Match is defined in [UTS #10].

Error Conditions

A dynamic error may be raised [err:FOCH0004] if the specified collation does not support collation units.

Examples

Variables
let $coll := "http://www.w3.org/2013/collation/UCA?lang=en;alternate=blanked;strength=primary"

Expression	Result
The collation used in some of these examples, `$coll`, is a collation in which both `-` and `*` are ignorable collation units.
“Ignorable collation unit” is equivalent to “ignorable collation element” in [UTS #10].
`ends-with("tattoo", "tattoo")`	true()
`ends-with("tattoo", "atto")`	false()
`ends-with((), ())`	true()
ends-with( "abcdefghi", "-g-h-i-", $coll )	true()
ends-with( "abcd**e---f--*ghi", "defghi", $coll )	true()
ends-with( "abcd**e---f--*ghi", "defghi", $coll )	true()
ends-with( (), "--**----", $coll )	true() (The second argument contains only ignorable collation units and is equivalent to the zero-length string.)
ends-with( "abcdefghi", "ghi-", $coll )	true()

5.5.4 fn:substring-before

Summary

Returns the part of $value that precedes the first occurrence of $substring, taking collations into account.

Signature

`fn:substring-before`(
`$value`	`as` `xs:string?`,
`$substring`	`as` `xs:string?`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:string`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

The three-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI.

Rules

If $value or $substring is the empty sequence, or contains only ignorable collation units, it is interpreted as the zero-length string.

If $substring is the zero-length string, then the function returns the zero-length string.

If $value does not contain a string that is equal to $substring, then the function returns the zero-length string.

The collation used by this function is determined according to the rules in 5.3.5 Choosing a collation.

The function returns the substring of $value that precedes in $value the first occurrence of a sequence of collation units that provides a minimal match to the collation units of $substring according to the collation that is used.

Note:

Minimal match is defined in [UTS #10].

Error Conditions

A dynamic error may be raised [err:FOCH0004] if the specified collation does not support collation units.

Examples

Variables
let $coll := "http://www.w3.org/2013/collation/UCA?lang=en;alternate=blanked;strength=primary"

Expression	Result
The collation used in some of these examples, `$coll`, is a collation in which both `-` and `*` are ignorable collation units.
“Ignorable collation unit” is equivalent to “ignorable collation element” in [UTS #10].
`substring-before("tattoo", "attoo")`	"t"
`substring-before("tattoo", "tatto")`	""
`substring-before((), ())`	""
substring-before( "abcdefghi", "--d-e-", $coll )	"abc"
substring-before( "abc--d-e-fghi", "--d-e-", $coll )	"abc--"
substring-before( "abcdefghi", "**cde", $coll )	"ab"
substring-before( "Eureka!", "--**----", $coll )	"" (The second argument contains only ignorable collation units and is equivalent to the zero-length string.)

5.5.5 fn:substring-after

Summary

Returns the part of $value that follows the first occurrence of $substring, taking collations into account.

Signature

`fn:substring-after`(
`$value`	`as` `xs:string?`,
`$substring`	`as` `xs:string?`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:string`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

The three-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI.

Rules

If $value or $substring is the empty sequence, or contains only ignorable collation units, it is interpreted as the zero-length string.

If $substring is the zero-length string, then the function returns the value of $value.

If $value does not contain a string that is equal to $substring, then the function returns the zero-length string.

The collation used by this function is determined according to the rules in 5.3.5 Choosing a collation.

The function returns the substring of $value that follows in $value the first occurrence of a sequence of collation units that provides a minimal match to the collation units of $substring according to the collation that is used.

Note:

Minimal match is defined in [UTS #10].

Error Conditions

A dynamic error may be raised [err:FOCH0004] if the specified collation does not support collation units.

Examples

Variables
let $coll := "http://www.w3.org/2013/collation/UCA?lang=en;alternate=blanked;strength=primary"

Expression	Result
The collation used in some of these examples, `$coll`, is a collation in which both `-` and `*` are ignorable collation units.
“Ignorable collation unit” is equivalent to “ignorable collation element” in [UTS #10].
`substring-after("tattoo", "tat")`	"too"
`substring-after("tattoo", "tattoo")`	""
`substring-after((), ())`	""
substring-after( "abcdefghi", "--d-e-", $coll )	"fghi"
substring-after( "abc--d-e-fghi", "--d-e-", $coll )	"-fghi"
substring-after( "abcdefghi", "cde*", $coll )	"fghi*"
substring-after( "Eureka!", "--**----", $coll )	"Eureka!" (The second argument contains only ignorable collation units and is equivalent to the zero-length string.)

5.6 String functions that use regular expressions

The four functions described in this section make use of a regular expression syntax for pattern matching, described below.

Function	Meaning
`fn:matches`	Returns `true` if the supplied string matches a given regular expression.
`fn:replace`	Returns a string produced from the input string by replacing any substrings that match a given regular expression with a supplied replacement string, provided either literally, or by invoking a supplied function.
`fn:tokenize`	Returns a sequence of strings constructed by splitting the input wherever a separator is found; the separator is any substring that matches a given regular expression.
`fn:analyze-string`	Analyzes a string using a regular expression, returning an XML structure that identifies which parts of the input string matched or failed to match the regular expression, and in the case of matched substrings, which substrings matched each capturing group in the regular expression.

5.6.1 Regular expression syntax

The regular expression syntax used by these functions is defined in terms of the regular expression syntax specified in XML Schema (see [XML Schema Part 2: Datatypes Second Edition]), which in turn is based on the established conventions of languages such as Perl. However, because XML Schema uses regular expressions only for validity checking, it omits some facilities that are widely used with languages such as Perl. This section, therefore, describes extensions to the XML Schema regular expressions syntax that reinstate these capabilities.

Note:

It is recommended that implementers consult [UTS #18] for information on using regular expression processing on Unicode characters.

The regular expression syntax and semantics are identical to those defined in [XML Schema Part 2: Datatypes Second Edition] with the additions described in the following subsections.

Note:

In [Schema 1.1 Part 2] there are no substantive technical changes to the syntax or semantics of regular expressions relative to XSD 1.0, but a number of errors and ambiguities have been resolved. For example, the rules for the interpretation of hyphens within square brackets in a regular expression have been clarified; and the semantics of regular expressions are no longer tied to a specific version of Unicode.

Implementers, even in cases where XSD 1.1 is not supported, are advised to consult the XSD 1.1 regular expression specification for guidance on how to handle cases where the XSD 1.0 specification is unclear or inconsistent.

5.6.1.1 Matching the Start and End of the String

Two meta-characters, ^ and $ are added. By default, the meta-character ^ matches the start of the entire string, while $ matches the end of the entire string. In multi-line mode, ^ matches the start of any line (that is, the start of the entire string, and the position immediately after a newline character), while $ matches the end of any line (that is, the end of the entire string, and the position immediately before a newline character). Newline here means the character #x0A only.

This means that the production in [XML Schema Part 2: Datatypes Second Edition]:

[10] Char ::= [^.\?*+()|#x5B#x5D]

is modified to read:

[10] Char ::= [^.\?*+{}()|^$#x5B#x5D]

The XSD 1.1 grammar for regular expressions uses the same production rule, but renumbered and renamed [73] NormalChar; it is affected in the same way.

The characters #x5B and #x5D correspond to [ and ] respectively.

Note:

The definition of Char (production [10]) in [XML Schema Part 2: Datatypes Second Edition] has a known error in which it omits the left brace ({) and right brace (}). That error is corrected here.

The following production:

[11] charClass ::= charClassEsc | charClassExpr | WildCardEsc

is modified to read:

[11] charClass ::= charClassEsc | charClassExpr | WildCardEsc | "^" | "$"

Using XSD 1.1 as the baseline the equivalent is to change the production:

[74] charClass ::= SingleCharEsc | charClassEsc | charClassExpr | WildCardEsc

to read:

Single character escapes are extended to allow the $ character to be escaped. Furthermore, the # character may be escaped: see 5.6.1.6 Comments. The following production is changed:

[24]SingleCharEsc ::= '\' [nrt\|.?*+(){}#x2D#x5B#x5D#x5E]

[24]SingleCharEsc ::= '\' [nrt\|.?*+(){}$#x2D#x5B#x5D#x5E\#]

(In the XSD 1.1 version of the regular expression grammar, the production rule for SingleCharEsc is unchanged from 1.0, but is renumbered [84])

5.6.1.2 Reluctant Quantifiers

Reluctant quantifiers are supported. They are indicated by a ? following a quantifier. Specifically:

X?? matches X, once or not at all
X*? matches X, zero or more times
X+? matches X, one or more times
X{n}? matches X, exactly n times
X{n,}? matches X, at least n times
X{n,m}? matches X, at least n times, but not more than m times

The effect of these quantifiers is that the regular expression matches the shortest possible substring consistent with the match as a whole succeeding. Without the ? , the regular expression matches the longest possible substring.

To achieve this, the production in [XML Schema Part 2: Datatypes Second Edition]:

[4] quantifier ::= [?*+] | ( '{' quantity '}' )

is changed to:

[4] quantifier ::= ( [?*+] | ( '{' quantity '}' ) ) '?'?

(In the XSD 1.1 version of the regular expression grammar, this rule is unchanged from 1.0, but is renumbered [67])

Note:

Reluctant quantifiers have no effect on the results of the boolean fn:matches function, since this function is only interested in discovering whether a match exists, and not where it exists.

5.6.1.3 Captured Sub-Expressions

Sub-expressions (groups) within the regular expression are recognized. The regular expression syntax defined by [XML Schema Part 2: Datatypes Second Edition] allows a regular expression to contain parenthesized sub-expressions, but attaches no special significance to them. Some operations associated with regular expressions (for example, back-references, and the fn:replace function) allow access to the parts of the input string that matched a sub-expression (called captured substrings).

[Definition] A left parenthesis is recognized as a capturing left parenthesis provided it is not immediately followed by ?: (see below), is not within a character group (square brackets), and is not escaped with a backslash. The sub-expression enclosed by a capturing left parenthesis and its matching right parenthesis is referred to as a capturing sub-expression.

More specifically, the ·capturing sub-expression· enclosed by the Nth capturing left parenthesis within the regular expression (determined by its character position in left-to-right order, and counting from one) is referred to as the Nth capturing sub-expression.

For example, in the regular expression A(BC(?:D(EF(GH[()])))), the string matched by the sub-expression BC(?:D(EF(GH[()]))) is capturing sub-expression 1, the string matched by EF(GH[()]) is capturing sub-expression 2, and the string matched by GH[()] is capturing sub-expression 3.

When, in the course of evaluating a regular expression, a particular substring of the input matches a capturing sub-expression, that substring becomes available as a captured substring. The string matched by the Nth capturing sub-expression is referred to as the Nth captured substring. By convention, the substring captured by the entire regular expression is treated as captured substring 0 (zero).

When a ·capturing sub-expression· is matched more than once (because it is within a construct that allows repetition), then only the last substring that it matched will be captured. Note that this rule is not sufficient in all cases to ensure an unambiguous result, especially in cases where (a) the regular expression contains nested repeating constructs, and/or (b) the repeating construct matches a zero-length string. In such cases it is implementation-dependent which substring is captured. For example given the regular expression (a*)+ and the input string "aaaa", an implementation might legitimately capture either "aaaa" or a zero length string as the content of the captured subgroup.

Parentheses that are required to group terms within the regular expression, but which are not required for capturing of substrings, can be represented using the syntax (?:xxxx). To achieve this, the production rule for atom in [XML Schema Part 2: Datatypes Second Edition] is changed to replace the alternative:

( '(' regExp ')' )

with:

( '(' '?:'? regExp ')' )

(For the new versions of the XSD 1.0 and XSD 1.1 production rules for atom, see below.)

In the absence of back-references (see below), the presence of the optional ?: has no effect on the set of strings that match the regular expression, but causes the left parenthesis not to be counted by operations (such as fn:replace and back-references) that number the capturing sub-expressions within a regular expression.

5.6.1.4 Back-References

Back-references are allowed outside a character class expression. A back-reference is an additional kind of atom. The construct \N where N is a single digit is always recognized as a back-reference; if this is followed by further digits, these digits are taken to be part of the back-reference if and only if the resulting number NN is such that the back-reference is preceded by the opening parenthesis of the NNth capturing left parenthesis. The regular expression is invalid if a back-reference refers to a capturing sub-expression that does not exist or whose closing right parenthesis occurs after the back-reference.

A back-reference with number N matches a string that is the same as the value of the Nth captured substring.

For example, the regular expression ('|").*\1 matches a sequence of characters delimited either by an apostrophe at the start and end, or by a quotation mark at the start and end.

If no string has been matched by the Nth capturing sub-expression, the back-reference is interpreted as matching a zero-length string.

Combining this change with the introduction of non-capturing groups (see above), back-references change the following production:

[9] atom ::= Char | charClass | ( '(' regExp ')' )

[9] atom ::= Char | charClass | ( '(' '?:'? regExp ')' ) | backReference

[9a] backReference ::= "\" [1-9][0-9]*

With respect to the XSD 1.1 version of the regular expression grammar, the effect is to change:

[72] atom ::= NormalChar | charClass | ( '(' regExp ')' )

[72] atom ::= NormalChar | charClass | ( '(' '?:'? regExp ')' ) | backReference

[72a] backReference ::= "\" [1-9][0-9]*

Note:

Within a character class expression, \ followed by a digit is invalid. Some other regular expression languages interpret this as an octal character reference.

5.6.1.5 Unicode Block Names

A regular expression that uses a Unicode block name that is not defined in the version(s) of Unicode supported by the processor (for example \p{IsBadBlockName}) is deemed to be invalid [err:FORX0002].

Note:

XSD 1.0 does not say how this situation should be handled; XSD 1.1 says that it should be handled by treating all characters as matching.

5.6.1.6 Comments

Comments are enabled in regular expressions if the c flag is present.

A comment starts with a # character that is not escaped with an immediately preceding backslash, and that is not contained in a CharClassExpr (that is, in square brackets). It ends with the following # character, or with the end of the string containing the regular expression.

Whether or not the c flag is present, the production for SingleCharEsc is extended to allow the # character to be escaped.

5.6.2 Flags

All these functions provide an optional parameter, $flags, to set options for the interpretation of the regular expression. The parameter accepts a xs:string, in which individual letters are used to set options. The presence of a letter within the string indicates that the option is on; its absence indicates that the option is off. Letters may appear in any order and may be repeated. They are case-sensitive. If there are characters present that are not defined here as flags, then a dynamic error is raised [err:FORX0001].

The following options are defined:

s: If present, the match operates in “dot-all” mode. (Perl calls this the single-line mode.) If the s flag is not specified, the meta-character . matches any character except a newline (#x0A) or carriage return (#x0D) character. In dot-all mode, the meta-character . matches any character whatsoever. Suppose the input contains the strings "hello" and "world" on two lines. This will not be matched by the regular expression "hello.*world" unless dot-all mode is enabled.
m: If present, the match operates in multi-line mode. By default, the meta-character ^ matches the start of the entire string, while $ matches the end of the entire string. In multi-line mode, ^ matches the start of any line (that is, the start of the entire string, and the position immediately after a newline character other than a newline that appears as the last character in the string), while $ matches the end of any line (that is, the position immediately before a newline character, and the end of the entire string if there is no newline character at the end of the string). Newline here means the character #x0A only.
i: If present, the match operates in case-insensitive mode. The detailed rules are as follows. In these rules, a character C2 is considered to be a case-variant of another character C1 if the following XPath expression returns true when the two characters are considered as strings of length one, and the ·Unicode codepoint collation· is used:

fn:lower-case(C1) eq fn:lower-case(C2) or fn:upper-case(C1) eq fn:upper-case(C2)

Note that the case-variants of a character under this definition are always single characters.
1. When a normal character (Char) is used as an atom, it represents the set containing that character and all its case-variants. For example, the regular expression "z" will match both "z" and "Z".
2. A character range (production charRange in the XSD 1.0 grammar, replaced by productions charRange and singleChar in XSD 1.1) represents the set containing all the characters that it would match in the absence of the i flag, together with their case-variants. For example, the regular expression "[A-Z]" will match all the letters A to Z and all the letters a to z. It will also match certain other characters such as #x212A (KELVIN SIGN), since fn:lower-case("#x212A") is k.
  
  This rule applies also to a character range used in a character class subtraction (charClassSub): thus [A-Z-[IO]] will match characters such as A, B, a, and b, but will not match I, O, i, or o.
  
  The rule also applies to a character range used as part of a negative character group: thus "[^Q]" will match every character except Q and q (these being the only case-variants of Q in Unicode).
3. A back-reference is compared using case-blind comparison: that is, each character must either be the same as the corresponding character of the previously matched string, or must be a case-variant of that character. For example, the strings "Mum", "mom", "Dad", and "DUD" all match the regular expression "([md])[aeiou]\1" when the i flag is used.
4. All other constructs are unaffected by the i flag. For example, "\p{Lu}" continues to match upper-case letters only.
x: If present, whitespace characters (#x9, #xA, #xD and #x20) in the regular expression are removed prior to matching with one exception: whitespace characters within character class expressions (charClassExpr) are not removed. This flag can be used, for example, to break up long regular expressions into readable lines.

Examples:

fn:matches("helloworld", "hello world", "x") returns true()

fn:matches("helloworld", "hello[ ]world", "x") returns false()

fn:matches("hello world", "hello\ sworld", "x") returns true()

fn:matches("hello world", "hello world", "x") returns false()

Note:

Whitespace is treated as a lexical construct to be removed before the regular expression is parsed; it is therefore not explicit in the regular expression grammar.
q: if present, all characters in the regular expression are treated as representing themselves, not as metacharacters. In effect, every character that would normally have a special meaning in a regular expression is implicitly escaped by preceding it with a backslash.

Furthermore, when this flag is present, the characters $ and \ have no special significance when used in the replacement string supplied to the fn:replace function.

This flag can be used in conjunction with the i flag. If it is used together with the m, s, x, or c flag, that flag has no effect.

Examples:

fn:tokenize("12.3.5.6", ".", "q") returns ("12", "3", "5", "6")

fn:replace("a\b\c", "\", "\\", "q") returns "a\\b\\c"

fn:replace("a/b/c", "/", "$", "q") returns "a$b$c"

fn:matches("abcd", ".*", "q") returns false()

fn:matches("Mr. B. Obama", "B. OBAMA", "iq") returns true()
c: if present, comments are enabled in the regular expression. This flag has no effect if the q flag is present. A comment is recognized by the presence of a # character that is not escaped by a backslash or contained in a character class expression (charClassExpr), and it is terminated by the following # character or by the end of the regular expression string.

For example:

fn:replace("03/24/2025", "(..#month#)/(..#day#)/(....#year#)", "$3-$1-$2", "c")

Note:

Comments are treated as a lexical construct to be removed before the regular expression is parsed; they are therefore not explicit in the regular expression grammar.

5.6.3 fn:matches

Summary

Returns true if the supplied string matches a given regular expression.

Signature

`fn:matches`(
`$value`	`as` `xs:string?`,
`$pattern`	`as` `xs:string`,
`$flags`	`as` `xs:string?`	`:=` `""`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, it is interpreted as the zero-length string.

If the $flags argument is omitted or if it is an empty sequence, the effect is the same as setting $flags to a zero-length string. Flags are defined in 5.6.2 Flags.

The function returns true if $value or some substring of $value matches the regular expression supplied as $pattern, and the associated $flags. Otherwise, the function returns false.

Error Conditions

A dynamic error is raised [err:FORX0002] if $pattern is invalid according to the rules described in 5.6.1 Regular expression syntax.

A dynamic error is raised [err:FORX0001] if $flags is invalid according to the rules described in 5.6.2 Flags.

Notes

Unless the metacharacters ^ and $ are used as anchors, the string is considered to match the pattern if any substring matches the pattern. But if anchors are used, the anchors must match the start/end of the string (in string mode), or the start/end of a line (in multi-line mode).

This is different from the behavior of patterns in [XML Schema Part 2: Datatypes Second Edition], where regular expressions are implicitly anchored.

Regular expression matching is defined on the basis of Unicode code points; it takes no account of collations.

Examples

Variables
let $poem := <poem author="Wilhelm Busch"> Kaum hat dies der Hahn gesehen, Fängt er auch schon an zu krähen: Kikeriki! Kikikerikih!! Tak, tak, tak! - da kommen sie. </poem>

Expression	Result
`matches("abracadabra", "bra")`	true()
`matches("abracadabra", "^a.*a$")`	true()
`matches("abracadabra", "^bra")`	false()
Given the source document:
the following function calls produce the following results, with the `poem` element as the context node:
`matches($poem, "Kaum.*krähen")`	false()
`matches($poem, "Kaum.*krähen", "s")`	true()
`matches($poem, "^Kaum.*gesehen,$", "m")`	true()
`matches($poem, "^Kaum.*gesehen,$")`	false()
`matches($poem, "kiki", "i")`	true()

5.6.4 fn:replace

Summary

Returns a string produced from the input string by replacing any substrings that match a given regular expression with a supplied replacement string, provided either literally, or by invoking a supplied function.

Signature

`fn:replace`(
`$value`	`as` `xs:string?`,
`$pattern`	`as` `xs:string`,
`$replacement`	`as` `xs:string?`	`:=` `()`,
`$flags`	`as` `xs:string?`	`:=` `''`,
`$action`	`as` `(function(xs:untypedAtomic, xs:untypedAtomic*) as item()?)?`	`:=` `()`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, it is interpreted as the zero-length string.

The replacement string is determined by the values of the $replacement and/or $action arguments:

If the $action argument is present and is not an empty sequence, the string is obtained by calling the $action function.

The first argument to the $action function is the string to be replaced, provided as xs:untypedAtomic.

The second argument to the $action function provides the captured substrings as an xs:untypedAtomic sequence. The Nth item in this sequence is the substring captured by the Nth parenthesized sub-expression. If the Nth parenthesized sub-expression was not matched, the Nth item will be the zero-length string.

Note that the rules for function coercion mean that the function actually supplied for the $action parameter may be an arity-1 function: the second argument does not need to be declared if it is not used.

The replacement string is obtained by invoking fn:string for the result of the function call.
Otherwise, if the $replacement argument is present and is not an empty sequence, the replacement string is the value of $replacement.
Otherwise, the replacement string is the zero-length string.

If the $flags argument is omitted or if it is an empty sequence, the effect is the same as setting $flags to a zero-length string. Flags are defined in 5.6.2 Flags.

The function returns the xs:string that is obtained by replacing each non-overlapping substring of $value that matches the given $pattern with a replacement string.

If two overlapping substrings of $value both match the $pattern, then only the first one (that is, the one whose first ·character· comes first in the $value string) is replaced.

If the q flag is present, or if the replacement string was obtained by calling the $action function, then the replacement string is used as is.

Otherwise, within the replacement string, a variable $N may be used to refer to the substring captured by the Nth parenthesized sub-expression in the regular expression. For each match of the pattern, these variables are assigned the value of the content matched by the relevant sub-expression, and the modified replacement string is then substituted for the ·characters· in $value that matched the pattern. $0 refers to the substring captured by the regular expression as a whole.

More specifically, the rules are as follows, where S is the number of parenthesized sub-expressions in the regular expression, and N is the decimal number formed by taking all the digits that consecutively follow the $ character:

If N=0, then the variable is replaced by the substring matched by the regular expression as a whole.
If 1<=N<=S, then the variable is replaced by the substring captured by the Nth parenthesized sub-expression. If the Nth parenthesized sub-expression was not matched, then the variable is replaced by the zero-length string.
If S<N<=9, then the variable is replaced by the zero-length string.
Otherwise (if N>S and N>9), the last digit of N is taken to be a literal character to be included “as is” in the replacement string, and the rules are reapplied using the number N formed by stripping off this last digit.

For example, if the replacement string is "$23" and there are 5 substrings, the result contains the value of the substring that matches the second sub-expression, followed by the digit 3.

Unless the q flag is used, a literal $ character within the replacement string must be written as \$, and a literal \ character must be written as \\.

If two alternatives within the pattern both match at the same position in the $input, then the match that is chosen is the one matched by the first alternative. For example:

 replace("abcd", "(ab)|(a)", "[1=$1][2=$2]") returns "[1=ab][2=]cd"

Error Conditions

A dynamic error is raised [err:FORX0002] if the value of $pattern is invalid according to the rules described in section 5.6.1 Regular expression syntax.

A dynamic error is raised [err:FORX0001] if the value of $flags is invalid according to the rules described in section 5.6.2 Flags.

A dynamic error is raised [err:FORX0003] if the pattern matches a zero-length string, that is, if the expression fn:matches("", $pattern, $flags) returns true. It is not an error, however, if a captured substring is zero-length.

In the absence of the q flag, a dynamic error is raised [err:FORX0004] if the value of $replacement contains a dollar sign ($) character that is not immediately followed by a digit 0-9 and not immediately preceded by a backslash (\).

In the absence of the q flag, a dynamic error is raised [err:FORX0004] if the value of $replacement contains a backslash (\) character that is not part of a \\ pair, unless it is immediately followed by a dollar sign ($) character.

A dynamic error is raised [err:FORX0005] if both the $replacement and $action arguments are supplied, and neither is an empty sequence.

Notes

If the input string contains no substring that matches the regular expression, the result of the function is a single string identical to the input string.

Examples

Expression:	`replace("abracadabra", "bra", "*")`
Result:	"acada"
Expression:	`replace("abracadabra", "a.a", "")`
Result:	"*"
Expression:	`replace("abracadabra", "a.?a", "")`
Result:	"cbra"
Expression:	`replace("abracadabra", "a", "")`
Result:	"brcdbr"
Expression:	`replace("abracadabra", "a(.)", "a$1$1")`
Result:	"abbraccaddabbra"
Expression:	`replace("AAAA", "A+", "b")`
Result:	"b"
Expression:	`replace("AAAA", "A+?", "b")`
Result:	"bbbb"
Expression:	`replace("darted", "^(.?)d(.)$", "$1c$2")`
Result:	"carted" (The first `d` is replaced.)
Expression:	replace("abracadabra", "bra", action := fn { "*" })
Result:	"acada"
Expression:	replace( "abracadabra", "bra", action := upper-case#1 )
Result:	"aBRAcadaBRA"
Expression:	replace("Chapter 9", "[0-9]+", action := fn { . + 1 })
Result:	"Chapter 10"
Expression:	replace( "LHR to LAX", "[A-Z]{3}", action := map { 'LAX': 'Los Angeles', 'LHR': 'London' } )
Result:	"London to Los Angeles"
Expression:	replace( "57°43′30″", "([0-9]+)°([0-9]+)′([0-9]+)″", action := function($s, $groups) { string($groups[1] + $groups[2] ÷ 60 + $groups[3] ÷ 3600) \|\| '°' } )
Result:	"57.725°"
The expression `fn:replace("abracadabra", ".*?", "$1")` raises an error, because the pattern matches the zero-length string

History

Changed in 4.0: $action argument new in 4.0. Accepted 2023-07-18.

5.6.5 fn:tokenize

Summary

Returns a sequence of strings constructed by splitting the input wherever a separator is found; the separator is any substring that matches a given regular expression.

Signature

`fn:tokenize`(
`$value`	`as` `xs:string?`,
`$pattern`	`as` `xs:string?`	`:=` `()`,
`$flags`	`as` `xs:string?`	`:=` `""`
) `as` `xs:string*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The following rules apply when the $pattern argument is omitted, or is set to an empty sequence:

The function splits the supplied string at whitespace boundaries.
More specifically, calling fn:tokenize($value) or fn:tokenize($value, ()) is equivalent to calling fn:tokenize(fn:normalize-space($value), ' ')) where the second argument is a single space character (x20).
The $flags argument is ignored.

The following rules apply when the $pattern argument is supplied as a single string:

If the $flags argument is omitted or if it is an empty sequence, the effect is the same as setting $flags to a zero-length string. Flags are defined in 5.6.2 Flags.
If $value is the empty sequence, or if $value is the zero-length string, the function returns the empty sequence.
The function returns a sequence of strings formed by breaking the $value string into a sequence of strings, treating any substring that matches $pattern as a separator. The separators themselves are not returned.
If a separator occurs at the start of the $value string, the result sequence will start with a zero-length string. Similarly, zero-length strings will also occur in the result sequence if a separator occurs at the end of the $value string, or if two adjacent substrings match the supplied $pattern.
If two alternatives within the supplied $pattern both match at the same position in the $value string, then the match that is chosen is the first. For example:
```
 tokenize("abracadabra", "(ab)|(a)") returns ("", "r", "c", "d", "r", "")
```

Error Conditions

A dynamic error is raised [err:FORX0002] if the value of $pattern is invalid according to the rules described in section 5.6.1 Regular expression syntax.

A dynamic error is raised [err:FORX0001] if the value of $flags is invalid according to the rules described in section 5.6.2 Flags.

A dynamic error is raised [err:FORX0003] if the supplied $pattern matches a zero-length string, that is, if fn:matches("", $pattern, $flags) returns true.

Notes

If the input string is not zero length, and no separators are found in the input string, the result of the function is a single string identical to the input string.

The one-argument form of the function has a similar effect to the two-argument form with \s+ as the separator pattern, except that the one-argument form strips leading and trailing whitespace, whereas the two-argument form delivers an extra zero-length token if leading or trailing whitespace is present.

The function returns no information about the separators that were found in the string. If this information is required, the fn:analyze-string function can be used instead.

The separator used by the one-argument form of the function is any sequence of tab (x09), newline (x0A), carriage return (x0D) or space (x20) characters. This is the same as the separator recognized by list-valued attributes as defined in XSD. It is not the same as the separator recognized by list-valued attributes in HTML5, which also treats form-feed (x0C) as whitespace. If it is necessary to treat form-feed as a separator, an explicit separator pattern should be used.

Examples

Expression:	`tokenize(" red green blue ")`
Result:	("red", "green", "blue")
Expression:	`tokenize("The cat sat on the mat", "\s+")`
Result:	("The", "cat", "sat", "on", "the", "mat")
Expression:	`tokenize(" red green blue ", "\s+")`
Result:	("", "red", "green", "blue", "")
Expression:	`tokenize("1, 15, 24, 50", ",\s*")`
Result:	("1", "15", "24", "50")
Expression:	`tokenize("1,15,,24,50,", ",")`
Result:	("1", "15", "", "24", "50", "")
`fn:tokenize("abba", ".?")` raises the dynamic error [err:FORX0003].
Expression:	tokenize( "Some unparsed <br> HTML <BR> text", "\s<br>\s", "i" )
Result:	("Some unparsed", "HTML", "text")

History

Changed in 4.0: allow the second argument to be an empty sequence.

5.6.6 fn:analyze-string

Summary

Analyzes a string using a regular expression, returning an XML structure that identifies which parts of the input string matched or failed to match the regular expression, and in the case of matched substrings, which substrings matched each capturing group in the regular expression.

Signature

`fn:analyze-string`(
`$value`	`as` `xs:string?`,
`$pattern`	`as` `xs:string`,
`$flags`	`as` `xs:string?`	`:=` `""`
) `as` `element(fn:analyze-string-result)`

Properties

This function is ·nondeterministic·, ·context-independent·, and ·focus-independent·.

Rules

If the $flags argument is omitted or if it is an empty sequence, the effect is the same as setting $flags to a zero-length string. Flags are defined in 5.6.2 Flags.

If $value is the empty sequence the function behaves as if $value were the zero-length string. In this situation the result will be an element node with no children.

The function returns an element node whose local name is analyze-string-result. This element and all its descendant elements have the namespace URI http://www.w3.org/2005/xpath-functions. The namespace prefix is ·implementation-dependent·. The children of this element are a sequence of fn:match and fn:non-match elements. This sequence is formed by breaking the $value string into a sequence of strings, returning any substring that matches $pattern as the content of a match element, and any intervening substring as the content of a non-match element.

More specifically, the function starts at the beginning of the input string and attempts to find the first substring that matches the regular expression. If there are several matches, the first match is defined to be the one whose starting position comes first in the string. If several alternatives within the regular expression both match at the same position in the input string, then the match that is chosen is the first alternative that matches. For example, if the input string is The quick brown fox jumps and the regular expression is jump|jumps, then the match that is chosen is jump.

Having found the first match, the instruction proceeds to find the second and subsequent matches by repeating the search, starting at the first ·character· that was not included in the previous match.

The input string is thus partitioned into a sequence of substrings, some of which match the regular expression, others which do not match it. Each substring will contain at least one character. This sequence is represented in the result by the sequence of fn:match and fn:non-match children of the returned element node; the string value of the fn:match or fn:non-match element will be the corresponding substring of $input, and the string value of the returned element node will therefore be the same as $input.

The content of an fn:non-match element is always a single text node.

The content of a fn:match element, however, is in general a sequence of text nodes and fn:group element children. An fn:group element with a nr attribute having the integer value N identifies the substring captured by the Nth parenthesized sub-expression in the regular expression. For each capturing subexpression there will be at most one corresponding fn:group element in each fn:match element in the result.

If the function is called twice with the same arguments, it is ·implementation-dependent· whether the two calls return the same element node or distinct (but deep equal) element nodes. In this respect it is ·nondeterministic with respect to node identity·.

The base URI of the element nodes in the result is ·implementation-dependent·.

A schema is defined for the structure of the returned element: see C.1 Schema for the result of fn:analyze-string.

The result of the function will always be such that validation against this schema would succeed. However, it is ·implementation-defined· whether the result is typed or untyped, that is, whether the elements and attributes in the returned tree have type annotations that reflect the result of validating against this schema.

Error Conditions

A dynamic error is raised [err:FORX0002] if the value of $pattern is invalid according to the rules described in section 5.6.1 Regular expression syntax.

A dynamic error is raised [err:FORX0001] if the value of $flags is invalid according to the rules described in section 5.6.2 Flags.

A dynamic error is raised [err:FORX0003] if the supplied $pattern matches a zero-length string, that is, if fn:matches("", $pattern, $flags) returns true.

Notes

It is recommended that a processor that implements schema awareness should return typed nodes. The concept of “schema awareness”, however, is a matter for host languages to define and is outside the scope of the function library specification.

The declarations and definitions in the schema are not automatically available in the static context of the fn:analyze-string call (or of any other expression). The contents of the static context are host-language defined, and in some host languages are implementation-defined.

The schema defines the outermost element, analyze-string-result, in such a way that mixed content is permitted. In fact the element will only have element nodes (match and non-match) as its children, never text nodes. Although this might have originally been an oversight, defining the analyze-string-result element with mixed="true" allows it to be atomized, which is potentially useful (the atomized value will be the original input string), and the capability has therefore been retained for compatibility with the 3.0 version of this specification.

Examples

Expression	Result
In the following examples, the result document is shown in serialized form, with whitespace between the element nodes. This whitespace is not actually present in the result.
`analyze-string("The cat sat on the mat.", "\w+")`	<analyze-string-result xmlns="http://www.w3.org/2005/xpath-functions"> <match>The</match> <non-match> </non-match> <match>cat</match> <non-match> </non-match> <match>sat</match> <non-match> </non-match> <match>on</match> <non-match> </non-match> <match>the</match> <non-match> </non-match> <match>mat</match> <non-match>.</non-match> </analyze-string-result> (with whitespace added for legibility)
analyze-string( "2008-12-03", "^(\d+)\-(\d+)\-(\d+)$" )	<analyze-string-result xmlns="http://www.w3.org/2005/xpath-functions"> <match><group nr="1">2008</group>-<group nr="2" >12</group>-<group nr="3">03</group></match> </analyze-string-result> (with whitespace added for legibility)
analyze-string( "A1,C15,,D24, X50,", "([A-Z])([0-9]+)" )	<analyze-string-result xmlns="http://www.w3.org/2005/xpath-functions"> <match><group nr="1">A</group><group nr="2">1</group></match> <non-match>,</non-match> <match><group nr="1">C</group><group nr="2">15</group></match> <non-match>,,</non-match> <match><group nr="1">D</group><group nr="2">24</group></match> <non-match>, </non-match> <match><group nr="1">X</group><group nr="2">50</group></match> <non-match>,</non-match> </analyze-string-result> (with whitespace added for legibility)

6 Functions that manipulate URIs

This section specifies functions that manipulate URI values, either as instances of xs:anyURI or as strings.

Function	Meaning
`fn:resolve-uri`	Resolves a relative IRI reference against an absolute IRI.
`fn:encode-for-uri`	Encodes reserved characters in a string that is intended to be used in the path segment of a URI.
`fn:decode-from-uri`	Decodes URI-escaped characters in a string.
`fn:iri-to-uri`	Converts a string containing an IRI into a URI according to the rules of [RFC 3987].
`fn:escape-html-uri`	Escapes a URI in the same way that HTML user agents handle attribute values expected to contain URIs.

6.1 fn:resolve-uri

Summary

Resolves a relative IRI reference against an absolute IRI.

Signature

`fn:resolve-uri`(
`$href`	`as` `xs:string?`,
`$base`	`as` `xs:string?`	`:=` `()`
) `as` `xs:anyURI?`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on static base URI.

Rules

The function is defined to operate on IRI references as defined in [RFC 3987], and the implementation must permit all arguments that are valid according to that specification. In addition, the implementation may accept some or all strings that conform to the rules for (absolute or relative) Legacy Extended IRI references as defined in [Legacy extended IRIs for XML resource identification]. For the purposes of this section, the terms IRI and IRI reference include these extensions, insofar as the implementation chooses to support them.

The following rules apply in order:

If $href is the empty sequence, the function returns the empty sequence.
If $href is an absolute IRI (as defined above), then it is returned unchanged.
If the $base argument is not supplied, or is supplied as an empty sequence then:
1. If the static base URI in the static context is not absent, it is used as the effective value of $base.
2. Otherwise, a dynamic error is raised: [err:FONS0005].
The function resolves the relative IRI reference $href against the base IRI $base using the algorithm defined in [RFC 3986], adapted by treating any ·character· that would not be valid in an RFC3986 URI or relative reference in the same way that RFC3986 treats unreserved characters. No percent-encoding takes place.

Error Conditions

The first form of this function resolves $href against the value of the base-uri property from the static context. A dynamic error is raised [err:FONS0005] if the base-uri property is not initialized in the static context.

A dynamic error is raised [err:FORG0002] if $href is not a valid IRI according to the rules of RFC3987, extended with an implementation-defined subset of the extensions permitted in LEIRI, or if it is not a suitable relative reference to use as input to the RFC3986 resolution algorithm extended to handle additional unreserved characters.

A dynamic error is raised [err:FORG0002] if $base is not a valid IRI according to the rules of RFC3987, extended with an implementation-defined subset of the extensions permitted in LEIRI, or if it is not a suitable IRI to use as input to the chosen resolution algorithm (for example, if it is a relative IRI reference or, if it is a non-hierarchic URI, or if it contains a fragment identifier). In XPath 4.0, attempting to resolve against an absolute URI that includes a fragment identifier is no longer an error, the fragment identifier is simply ignored. A narrow reading of RFC 3986 might seem to forbid this, but in practice the interpretation is non-controversial and the practice is widely supported.

A dynamic error is raised [err:FORG0009] if the chosen resolution algorithm fails for any other reason.

Notes

Resolving a URI does not dereference it. This is merely a syntactic operation on two ·strings·.

The algorithms in the cited RFCs include some variations that are optional or recommended rather than mandatory; they also describe some common practices that are not recommended, but which are permitted for backwards compatibility. Where the cited RFCs permit variations in behavior, so does this specification.

Throughout this family of specifications, the phrase "resolving a relative URI (or IRI) reference" should be understood as using the rules of this function, unless otherwise stated.

RFC3986 defines an algorithm for resolving relative references in the context of the URI syntax defined in that RFC. RFC3987 describes a modification to that algorithm to make it applicable to IRIs (specifically: additional characters permitted in an IRI are handled the same way that RFC3986 handles unreserved characters). The LEIRI specification does not explicitly define a resolution algorithm, but suggests that it should not be done by converting the LEIRI to a URI, and should not involve percent-encoding. This specification fills this gap by defining resolution for LEIRIs in the same way that RFC3987 defines resolution for IRIs, that is by specifying that additional characters are handled as unreserved characters.

History

Changed in 4.0: The optional second argument can now be supplied as an empty sequence.

6.2 fn:encode-for-uri

Summary

Encodes reserved characters in a string that is intended to be used in the path segment of a URI.

Signature

`fn:encode-for-uri`(
`$value`	`as` `xs:string?`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the zero-length string.

This function applies the URI escaping rules defined in section 2 of [RFC 3986] to the xs:string supplied as $value. The effect of the function is to escape reserved characters. Each such character in the string is replaced with its percent-encoded form as described in [RFC 3986].

Since [RFC 3986] recommends that, for consistency, URI producers and normalizers should use uppercase hexadecimal digits for all percent-encodings, this function must always generate hexadecimal values using the upper-case letters A-F.

Notes

All characters are escaped except those identified as “unreserved” by [RFC 3986], that is the upper- and lower-case letters A to Z, the digits 0 to 9, HYPHEN-MINUS (-), LOW LINE (_), FULL STOP (.), and TILDE (~).

This function escapes URI delimiters and therefore cannot be used indiscriminately to encode “invalid” characters in a path segment.

This function is invertible but not idempotent. This is because a string containing a percent character will be modified by applying the function: for example 100% becomes 100%25, while 100%25 becomes 100%2525.

Examples

Expression:	encode-for-uri( "http://example.com/00/Weather/CA/Los%20Angeles#ocean" )
Result:	"http%3A%2F%2Fexample.com%2F00%2FWeather%2FCA%2FLos%2520Angeles%23ocean" (This is probably not what the user intended because all of the delimiters have been encoded.)
Expression:	concat( "http://example.com/", encode-for-uri("~bébé") )
Result:	"http://example.com/~b%C3%A9b%C3%A9"
Expression:	concat( "http://example.com/", encode-for-uri("100% organic") )
Result:	"http://example.com/100%25%20organic"

6.3 fn:decode-from-uri

Summary

Decodes URI-escaped characters in a string.

Signature

`fn:decode-from-uri`(
`$value`	`as` `xs:string?`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

This function returns the original representation of a URI-escaped string.

If $value is the empty sequence, the function returns the zero-length string.

Otherwise, the value is first converted to a sequence of octets. Each plus sign (+) is replaced with the octet representing a space character (x20), and any substring that matches the regular expression %[a-fA-F0-9][a-fA-F0-9] is replaced with an octet for the two-digit hexadecimal number that follows the percent sign. Characters that are not part of such a substring are replaced with the octets of their UTF-8 encoding. For example, "A%42+C" results in the octets x41, x42, x20, x43, and "💡" yields xF0, x9F, x92, and xA1.

If % is followed by up to two characters that are not hexadecimal digits, these characters are replaced by octets xEF, xBF, and xBD, that is, the UTF-8 encoding of the Unicode replacement character (0xFFFD). For example, the incomplete or invalid percent-encoded strings "%", "%X", "%AX", and "%XA" are all replaced with these octets. For the string "%1X!", the octets xEF, xBF, xBD, and x21 are returned.

Next, the resulting octets are interpreted as UTF-8. For example, x41, x42, x20, and x43 becomes "AB C", and xF0, x9F, x92, and xA1 becomes "💡".

If an invalid UTF-8 octet sequence is encountered, the octets that have successfully been parsed are replaced with a Unicode replacement character. Examples:

The single octet xF0 is converted to "�".
The octets xF0, x9F, x92, and x41 are converted to "�A": The bit pattern of the first octet indicates that the UTF-8 character comprises four octets. As the fourth octet is invalid, a Unicode replacement character is added for the first three octets, and the fourth (invalid) octet is parsed as a new character.
Similarly, the octets xF0, xF0, x9F, x92, and xA1 are converted to "�💡": The second octet is invalid, but it becomes valid when being parsed as the first octet of the remaining UTF-8 sequence.

Similarly, a UTF-8 octet sequence that represents a codepoint that is not a valid XML character is replaced with a Unicode replacement character. For example, x00 becomes "�".

Examples

Expression	Result
`decode-from-uri("http://example.com/")`	"http://example.com/"
`decode-from-uri("~b%C3%A9b%C3%A9?a=b+c")`	"~bébé?a=b c"
`decode-from-uri("%00-%XX-%F0%9F%92%41-%F0%F0%9F%92%A1")`	"�-�-�A-�💡"

6.4 fn:iri-to-uri

Summary

Converts a string containing an IRI into a URI according to the rules of [RFC 3987].

Signature

`fn:iri-to-uri`(
`$value`	`as` `xs:string?`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the zero-length string.

Otherwise, the function converts $value into a URI according to the rules given in Section 3.1 of [RFC 3987] by percent-encoding characters that are allowed in an IRI but not in a URI. If $value contains a character that is invalid in an IRI, such as the space character (see note below), the invalid character is replaced by its percent-encoded form as described in [RFC 3986] before the conversion is performed.

Notes

The function is idempotent but not invertible. Both the inputs My Documents and My%20Documents will be converted to the output My%20Documents.

This function does not check whether $iri is a valid IRI. It treats it as an ·string· and operates on the ·characters· in the string.

The following printable ASCII characters are invalid in an IRI: <, >, ", , {, }, |, \, ^, and `. Since these characters should not appear in an IRI, if they do appear in $iri they will be percent-encoded. In addition, characters outside the range x20-x7E will be percent-encoded because they are invalid in a URI.

Since this function does not escape the PERCENT SIGN % and this character is not allowed in data within a URI, users wishing to convert character strings (such as file names) that include % to a URI should manually escape % by replacing it with %25.

Examples

Expression:	iri-to-uri( "http://www.example.com/00/Weather/CA/Los%20Angeles#ocean" )
Result:	"http://www.example.com/00/Weather/CA/Los%20Angeles#ocean"
Expression:	`iri-to-uri("http://www.example.com/~bébé")`
Result:	"http://www.example.com/~b%C3%A9b%C3%A9"

6.5 fn:escape-html-uri

Summary

Escapes a URI in the same way that HTML user agents handle attribute values expected to contain URIs.

Signature

`fn:escape-html-uri`(
`$value`	`as` `xs:string?`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the zero-length string.

Otherwise, the function escapes all ·characters· except printable characters of the US-ASCII coded character set, specifically the ·codepoints· between 32 and 126 (decimal) inclusive. Each character in $uri to be escaped is replaced by an escape sequence, which is formed by encoding the character as a sequence of octets in UTF-8, and then representing each of these octets in the form %HH, where HH is the hexadecimal representation of the octet. This function must always generate hexadecimal values using the upper-case letters A-F.

Notes

The behavior of this function corresponds to the recommended handling of non-ASCII characters in URI attribute values as described in [HTML 4.0] Appendix B.2.1.

Examples

Expression:	escape-html-uri( "http://www.example.com/00/Weather/CA/Los Angeles#ocean" )
Result:	"http://www.example.com/00/Weather/CA/Los Angeles#ocean"
Expression:	escape-html-uri( "javascript:if (navigator.browserLanguage == 'fr') window.open('http://www.example.com/~bébé');" )
Result:	"javascript:if (navigator.browserLanguage == 'fr') window.open('http://www.example.com/~b%C3%A9b%C3%A9');"

6.6 Parsing and building URIs

This section specifies functions that parse strings as URIs, to identify their structure, and construct URI strings from their structured representation.

Some URI schemes are hierarchical and some are non-hierarchical. Implementations must treat the following schemes as non-hierarchical: jar, mailto, news, tag, tel, and urn. Whether additional schemes are known to be non-hierarchical ·implementation-defined·. If a scheme is not known to be non-hierarchical, it must be treated as hierarchical.

Function	Meaning
`fn:parse-uri`	Parses the URI provided and returns a map of its parts.
`fn:build-uri`	Constructs a URI from the parts provided.

The structured representation of a URI is described by the uri-structure-record:

`uri-structure-record`:
`record(`
`uri?`	`as` `xs:string?`,
`scheme?`	`as` `xs:string?`,
`hierarchical?`	`as` `xs:boolean?`,
`authority?`	`as` `xs:string?`,
`userinfo?`	`as` `xs:string?`,
`host?`	`as` `xs:string?`,
`port?`	`as` `xs:string?`,
`path?`	`as` `xs:string?`,
`query?`	`as` `xs:string?`,
`fragment?`	`as` `xs:string?`,
`path-segments?`	`as` `xs:string*`,
`query-parameters?`	`as` `map(xs:string, xs:string*)?`,
`*`
`)`

The parts of this structure are:

The URI structure record
uri	The original URI. This element is returned by `fn:parse-uri`, but ignored by `fn:build-uri`.
scheme	The URI scheme (e.g., “https” or “file”).
hierarchical	Whether the URI is hierarchical or not.
authority	The authority portion of the URI (e.g., “example.com:8080”).
userinfo	Any userinfo that was passed as part of the authority.
host	The host passed as part of the authority (e.g., “example.com”).
port	The port passed as part of the authority (e.g., “8080”).
path	The path portion of the URI.
query	Any query string.
fragment	Any fragment identifier.
path-segments	Parsed and unescaped path segments.
query-parameters	Parsed and unescaped query key-value pairs.
filepath	The path of the URI, treated as a filepath.
*	Additional, information defined structures are allowed.

The segmented forms of the path and query parameters provide convenient access to commonly used information.

The path, if there is one, is tokenized on “/” characters and each segment is unescaped (as per the fn:decode-from-uri function). Consider the URI http://example.com/path/to/a%2fb. The path portion has to be returned as /path/to/a%2fb because decoding the %2f would change the nature of the path. The unescaped form is easily accessible from path-segments:

("", "path", "to", "a/b")

Note that the presence or absence of a leading slash on the path will affect whether or not the sequence begins with an empty string.

The query parameters are decoded into a map. Consider the URI: http://example.com/path?a=1&b=2%264&a=3. The decoded form in the query-parameters is the following map:

{ "a": ("1", "3"),
  "b": "2&4",
}

Note that both keys and values are unescaped. If a key is repeated in the query string, the map will contain a sequence of values for that key, as seen for a in this example.

6.6.1 fn:parse-uri

Summary

Parses the URI provided and returns a map of its parts.

Signature

`fn:parse-uri`(
`$uri`	`as` `xs:string`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `uri-structure-record`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function parses the $uri provided, returning a map containing its constituent parts: scheme, authority components, path, etc. In addition to parsing URIs as defined by [RFC 3986] (and [RFC 3987]), this function also attempts to account for strings that are not valid URIs but that often appear in URI-adjacent spaces, such as file names. Not all such strings can be successfully parsed as URIs.

The following options are available:

Key	Meaning
`path-separator`	Identifies the path separator Type: `xs:string` Default: `/`
`query-separator`	Identifies the query separator Type: `xs:string` Default: `&`
`allow-deprecated-features`	Indicates that deprecated URI features should be returned Type: `xs:boolean` Default: `false()`
`omit-default-ports`	Indicates that a port number that is the same as the default port for a given scheme should be omitted. Type: `xs:boolean` Default: `false()`
`unc-path`	Indicates that an input URI that begins with two or more leading slashes should be interprted as a Windows Universal Naming Convention Path. (Specifically: that it has the `file:` scheme.) Type: `xs:boolean` Default: `false()`

This function is described as a series of transformations over the input string to identify the parts of a URI that are present. Some portions of the URI are identified by matching with a regular expression. This approach is designed to make the description clear and unambiguous; it is not implementation advice.

Processing begins with a string that is equal to the $uri. If the string contains any backslashes (\), replace them with forward slashes (/).

Strip off the fragment identifier and any query:

If the string matches ^(.*?)#(.*)$, the string is the first match group and the fragment is the second match group. Otherwise, the string is unchanged and the fragment is the empty sequence.

If the string matches ^(.*?)\?(.*)$, the string is the first match group and the query is the second match group. Otherwise, the string is unchanged and the query is the empty sequence.

Attempt to identify the scheme:

If the string matches ^[a-zA-Z][:|].*$:
- the scheme is file;
- if the second character in the string is |, it is changed to :;
- the filepath is the string; and
- a leading slash / is added to the string.
Otherwise, if the string matches ^([a-zA-Z][A-Za-z0-9\+\-\.]*):(.*)$:
- the scheme is the first match group,
- the string is the second match group, and
- the filepath is the empty sequence.
Finally, if the string does not match either expression:
- the scheme is the empty sequence,
- the string is unchanged, and
- the filepath is the empty sequence.

Now that the scheme, if there is one, has been identified, determine if the URI is hierarchical:

If the scheme is known to be hierarchical, or known not to be hierarchical, then hierarchical is set accordingly. If the implementation does not know if a scheme is or is not hierarchical, the hierarchical setting depends on the string: if the string is the empty string, hierarchical is the empty sequence (i.e. not known), otherwise hierarchical is true if string begins with / and false otherwise.

Then examine the remaining parts of the string.

If the scheme is the empty sequence, the unc-path option is true, and the string matches ^//[^/].*$, then the scheme is file, the authority is empty, and the filepath is the string.
Otherwise:
- If the scheme is not known or is known to be file and the string matches ^/*(/[a-zA-Z]:.*)$, the authority is empty and the string is the first match group.
- Otherwise, if the string matches ^///*([^/]+)?(/.*)?$, the authority is the first match group and the string is the second match group.
- Finally, if the string does not match either regular expression, the authority is the empty sequence and the string is unchanged.

If the authority matches ^(([^@]*)@)(.*)(:([^:]*))?$, then the userinfo is match group 2, otherwise userinfo is the empty sequence. If userinfo is present and contains a non-empty password, then userinfo is discarded and set to the empty sequence unless the allow-deprecated-features option is true.

When parsing the authority to find the host, there are four possibilities: the host can be a registered name (e.g., example.com), an IPv4 address (e.g., 127.0.0.1), an IPv6 (or IPvFuture) address (e.g., [::1]), or an error if there is an open square bracket ([) not matched by a close square bracket (]). In a properly constructed RFC 3986 URI, the only place where square brackets may occur is around the IPv6/IPvFuture IP address.

If the authority matches ^(([^@]*)@)?(\[[^\]]*\])(:([^:]*))?$, then the host is match group 3, otherwise
If the authority matches ^(([^@]*)@)?\[.*$ then [err:FOUR0001] is raised, otherwise
If the authority matches ^(([^@]*)@)?([^:]+)(:([^:]*))?$, then the host is match group 3, otherwise
the host is the empty sequence.

This function does not attempt to decode the components of the host.

Similar care must be taken to match the port because an IPv6/IPvFuture address may contain a colon.

If the authority matches ^(([^@]*)@)?(\[[^\]]*\])(:([^:]*))?$, then the port is match group 5.
Otherwise, if the authority matches ^(([^@]*)@)?([^:]+)(:([^:]*))?$, then the port is match group 5.
Otherwise, the port is the empty sequence.

If the omit-default-ports option is true, the port is discarded and set to the empty sequence if the port number is the same as the default port for the given scheme. Implementations should recognize the default ports for http (80), https (443), ftp (21), and ssh (22). Exactly which ports are recognized is ·implementation-defined·.

If the string is the empty string, then path is the empty sequence, otherwise path is the whole string. If the scheme is file or the empty sequence, and filepath is the empty sequence, filepath is also the whole string.

The path separator is the value of the path-separator option. A path-segments sequence is constructed by tokenizing the string on the path separator and applying uri decoding on each token.

Applying uri decoding is equivalent to calling fn:decode-from-uri on the string.

The query separator is the value of the query-separator option, and is used to construct a query-parameters value as follows. Start with an empty map. Tokenize the query on the query separator. For each token, identify the key and the value. If the token contains an equal sign (=), the key is the string that precedes the first equal sign, uri decoded, and the value is the remainder of the token, after the first equal sign, uri decoded. If the token does not contain an equal sign, key is the empty string and the value is equal to the token, uri decoded. Add the key/value pair to the map. If the key already exists in the map, add the value to a list of values associated with that key. The resulting map, when all tokens have been processed, is the query-parameters map.

If the filepath is not the empty sequence, it is uri decoded. On a Windows system, any forward slashes in the path may be replaced with backslashes.

The following map is returned:

{
  "uri": $uri,
  "scheme": scheme,
  "hierarchical": hierarchical,
  "authority": authority,
  "userinfo": userinfo,
  "host": host,
  "port": port,
  "path": path,
  "query": query,
  "fragment": fragment,
  "path-segments": path-segments,
  "query-parameters": query-parameters,
  "filepath": filepath
}

The map should be populated with only those keys that have a non-empty value (keys whose value is the empty sequence should be omitted).

Implementations may implement additional or different rules for URIs that have a scheme or pattern that they recognize. An implementation might choose to parse jar: URIs with special rules, for example, since they extend the syntax in ways not defined by [RFC 3986]. Implementations may add additional keys to the map. The meaning of those keys is implementation-defined.

Error Conditions

A dynamic error is raised [err:FOUR0001] if the URI contains an open square bracket in the authority component that is not followed by a close square bracket.

Notes

Like fn:resolve-uri, this function handles the additional characters allowed in [RFC 3987] IRIs in the same way that other unreserved characters are handled.

Unlike fn:resolve-uri, this function is not attempting to resolve one URI against another and consequently, the errors that can arise under those circumstances do not apply here. The fn:parse-uri function will accept strings that would raise errors if resolution was attempted; see fn:build-uri.

Examples

In the examples that follow, keys with values that are null or an empty sequence are elided for editorial clarity. String literals that include an ampersand character are written as string templates (for example `Barnes&Noble`) to ensure that the examples work in both XPath and XQuery.
Expression:	parse-uri( "http://qt4cg.org/specifications/xpath-functions-40/Overview.html#parse-uri" )
Result:	map { "uri": "http://qt4cg.org/specifications/xpath-functions-40/Overview.html#parse-uri", "scheme": "http", "hierarchical": true(), "authority": "qt4cg.org", "host": "qt4cg.org", "path": "/specifications/xpath-functions-40/Overview.html", "fragment": "parse-uri", "path-segments": ("", "specifications", "xpath-functions-40", "Overview.html") }
Expression:	`parse-uri("http://www.ietf.org/rfc/rfc2396.txt")`
Result:	map { "uri": "http://www.ietf.org/rfc/rfc2396.txt", "scheme": "http", "hierarchical": true(), "authority": "www.ietf.org", "host": "www.ietf.org", "path": "/rfc/rfc2396.txt", "path-segments": ("", "rfc", "rfc2396.txt") }
Expression:	`parse-uri("https://example.com/path/to/file")`
Result:	map { "uri": "https://example.com/path/to/file", "scheme": "https", "hierarchical": true(), "authority": "example.com", "host": "example.com", "path": "/path/to/file", "path-segments": ("", "path", "to", "file") }
Expression:	parse-uri( `https://example.com:8080/path?s=%22hello world%22&sort=relevance` )
Result:	map { "uri": `https://example.com:8080/path?s=%22hello world%22&sort=relevance`, "scheme": "https", "hierarchical": true(), "authority": "example.com:8080", "host": "example.com", "port": "8080", "path": "/path", "query": `s=%22hello world%22&sort=relevance`, "query-parameters": map { "s": '"hello world"', "sort": "relevance" }, "path-segments": ("", "path") }
Expression:	`parse-uri("https://user@example.com/path/to/file")`
Result:	map { "uri": "https://user@example.com/path/to/file", "scheme": "https", "hierarchical": true(), "authority": "user@example.com", "userinfo": "user", "host": "example.com", "path": "/path/to/file", "path-segments": ("", "path", "to", "file") }
Expression:	`parse-uri("ftp://ftp.is.co.za/rfc/rfc1808.txt")`
Result:	map { "uri": "ftp://ftp.is.co.za/rfc/rfc1808.txt", "scheme": "ftp", "hierarchical": true(), "authority": "ftp.is.co.za", "host": "ftp.is.co.za", "path": "/rfc/rfc1808.txt", "path-segments": ("", "rfc", "rfc1808.txt") }
Expression:	`parse-uri("file:////uncname/path/to/file")`
Result:	map { "uri": "file:////uncname/path/to/file", "scheme": "file", "hierarchical": true(), "authority": "uncname", "host": "uncname", "path": "/path/to/file", "filepath": "/path/to/file", "path-segments": ("", "path", "to", "file") }
Expression:	`parse-uri("file:///c:/path/to/file")`
Result:	map { "uri": "file:///c:/path/to/file", "scheme": "file", "hierarchical": true(), "path": "/c:/path/to/file", "filepath": "c:/path/to/file", "path-segments": ("", "c:", "path", "to", "file") }
Expression:	`parse-uri("file:/C:/Program%20Files/test.jar")`
Result:	map { "uri": "file:/C:/Program%20Files/test.jar", "scheme": "file", "hierarchical": true(), "path": "/C:/Program%20Files/test.jar", "filepath": "C:/Program Files/test.jar", "path-segments": ("", "C:", "Program Files", "test.jar") }
Expression:	`parse-uri("file:\\c:\path\to\file")`
Result:	map { "uri": "file:\\c:\path\to\file", "scheme": "file", "hierarchical": true(), "path": "/c:/path/to/file", "filepath": "c:/path/to/file", "path-segments": ("", "c:", "path", "to", "file") }
Expression:	`parse-uri("file:\c:\path\to\file")`
Result:	map { "uri": "file:\c:\path\to\file", "scheme": "file", "hierarchical": true(), "path": "/c:/path/to/file", "filepath": "c:/path/to/file", "path-segments": ("", "c:", "path", "to", "file") }
Expression:	`parse-uri("c:\path\to\file")`
Result:	map { "uri": "c:\path\to\file", "scheme": "file", "hierarchical": true(), "path": "/c:/path/to/file", "filepath": "c:/path/to/file", "path-segments": ("", "c:", "path", "to", "file") }
Expression:	`parse-uri("/path/to/file")`
Result:	map { "uri": "/path/to/file", "hierarchical": true(), "path": "/path/to/file", "filepath": "/path/to/file", "path-segments": ("", "path", "to", "file") }
Expression:	`parse-uri("#testing")`
Result:	map { "uri": "#testing", "fragment": "testing" }
Expression:	`parse-uri("?q=1")`
Result:	map { "uri": "?q=1", "query": "q=1", "query-parameters": map { "q": "1" } }
Expression:	`parse-uri("ldap://[2001:db8::7]/c=GB?objectClass?one")`
Result:	map { "uri": "ldap://[2001:db8::7]/c=GB?objectClass?one", "scheme": "ldap", "hierarchical": true(), "authority": "[2001:db8::7]", "host": "[2001:db8::7]", "path": "/c=GB", "query": "objectClass?one", "query-parameters": map { "": "objectClass?one" }, "path-segments": ("", "c=GB") }
Expression:	`parse-uri("mailto:John.Doe@example.com")`
Result:	map { "uri": "mailto:John.Doe@example.com", "scheme": "mailto", "hierarchical": false(), "path": "John.Doe@example.com", "path-segments": ("John.Doe@example.com") }
Expression:	`parse-uri("news:comp.infosystems.www.servers.unix")`
Result:	map { "uri": "news:comp.infosystems.www.servers.unix", "scheme": "news", "hierarchical": false(), "path": "comp.infosystems.www.servers.unix", "path-segments": ("comp.infosystems.www.servers.unix") }
Expression:	`parse-uri("tel:+1-816-555-1212")`
Result:	map { "uri": "tel:+1-816-555-1212", "scheme": "tel", "hierarchical": false(), "path": "+1-816-555-1212", "path-segments": (" 1-816-555-1212") }
Expression:	`parse-uri("telnet://192.0.2.16:80/")`
Result:	map { "uri": "telnet://192.0.2.16:80/", "scheme": "telnet", "hierarchical": true(), "authority": "192.0.2.16:80", "host": "192.0.2.16", "port": "80", "path": "/", "path-segments": ("", "") }
Expression:	parse-uri( "urn:oasis:names:specification:docbook:dtd:xml:4.1.2" )
Result:	map { "uri": "urn:oasis:names:specification:docbook:dtd:xml:4.1.2", "scheme": "urn", "hierarchical": false(), "path": "oasis:names:specification:docbook:dtd:xml:4.1.2", "path-segments": "oasis:names:specification:docbook:dtd:xml:4.1.2" }
Expression:	`parse-uri("tag:textalign.net,2015:ns")`
Result:	map { "uri": "tag:textalign.net,2015:ns", "scheme": "tag", "hierarchical": false(), "path": "textalign.net,2015:ns", "path-segments": "textalign.net,2015:ns" }
Expression:	`parse-uri("tag:jan@example.com,1999-01-31:my-uri")`
Result:	map { "uri": "tag:jan@example.com,1999-01-31:my-uri", "scheme": "tag", "hierarchical": false(), "path": "jan@example.com,1999-01-31:my-uri", "path-segments": "jan@example.com,1999-01-31:my-uri" }
This example uses the algorithm described above, not an algorithm that is specifically aware of the `jar:` scheme.
Expression:	parse-uri( "jar:file:/C:/Program%20Files/test.jar!/foo/bar" )
Result:	map { "uri": "jar:file:/C:/Program%20Files/test.jar!/foo/bar", "scheme": "jar", "hierarchical": false(), "path": "file:/C:/Program%20Files/test.jar!/foo/bar", "path-segments": ("file:", "C:", "Program Files", "test.jar!", "foo", "bar") }
This example demonstrates that parsing the URI treats non-URI characters in lexical IRIs as “unreserved characters”. The rationale for this is given in the description of `fn:resolve-uri`.
Expression:	`parse-uri("http://www.example.org/Dürst")`
Result:	map { "uri": "http://www.example.org/Dürst", "scheme": "http", "hierarchical": true(), "authority": "www.example.org", "host": "www.example.org", "path": "/Dürst", "path-segments": ("", "Dürst") }
This example demonstrates a non-standard query separator.
Expression:	parse-uri( "https://example.com:8080/path?s=%22hello world%22;sort=relevance", map { "query-separator": ";" } )
Result:	map { "uri": "https://example.com:8080/path?s=%22hello world%22;sort=relevance", "scheme": "https", "hierarchical": true(), "authority": "example.com:8080", "host": "example.com", "port": "8080", "path": "/path", "query": "s=%22hello world%22;sort=relevance", "query-parameters": map { "s": '"hello world"', "sort": "relevance" }, "path-segments": ("", "path") }
This example uses an invalid query separator so raises an error.
Expression:	parse-uri( "https://example.com:8080/path?s=%22hello world%22;;sort=relevance", map { "query-separator": ";;" } )
Result:	Raises error FOXX0000.
This example demonstrates the use of `\|` instead of `:` in a Windows path.
Expression:	`parse-uri("c\|/path/to/file")`
Result:	map { "uri": "c\|/path/to/file", "scheme": "file", "hierarchical": true(), "path": "/c:/path/to/file", "filepath": "c:/path/to/file", "path-segments": ("", "c:", "path", "to", "file") }
This example demonstrates the use of `\|` instead of `:` in a Windows path with an explicit `file:` scheme.
Expression:	`parse-uri("file://c\|/path/to/file")`
Result:	map { "uri": "file://c\|/path/to/file", "scheme": "file", "hierarchical": true(), "path": "/c:/path/to/file", "filepath": "c:/path/to/file", "path-segments": ("", "c:", "path", "to", "file") }

History

Proposed on 17 Oct 2022 to resolve issue #72. Accepted in principle on 15 Nov 2022, with some details still to be resolved. Updated in response to issue #389 and issue #390. Further updated on 13 September 2023 in response to comments from review in meeting 042.

6.6.2 fn:build-uri

Summary

Constructs a URI from the parts provided.

Signature

`fn:build-uri`(
`$parts`	`as` `uri-structure-record`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·.

Rules

A URI is composed from a scheme, authority, path, query, and fragment.

The following options are available:

Key	Meaning
`path-separator`	Identifies the path separator Type: `xs:string` Default: `/`
`query-separator`	Identifies the query separator Type: `xs:string` Default: `&`
`allow-deprecated-features`	Indicates that deprecated URI features should be returned Type: `xs:boolean` Default: `false()`
`omit-default-ports`	Indicates that a port number that is the same as the default port for a given scheme should be omitted. Type: `xs:boolean` Default: `false()`
`unc-path`	Indicates that the URI represents a Windows Universal Naming Convention Path. Type: `xs:boolean` Default: `false()`

The components are derived from the contents of the $parts map. To simplify the description below, a value is considered to be present in the map if the relevant field exists and is non-empty.

If the scheme key is present in the map, the URI begins with the value of that key. A URI is considered to be non-hierarchical if either the hierarchical key is present in the $parts map with the value false() or if the scheme is known to be non-hierarchical. (In other words, schemes are hierarchical by default.)

If the scheme is known to be non-hierarchical, it is delimited by a trailing :.
Otherwise, if the scheme is file and the unc-path option is true, the scheme is delimited by a trailing :////.
Otherwise, the scheme is delimited by a trailing ://.

For simplicity of exposition, we take the userinfo, host, and port values from the map and imagine they are stored in variables with the same name. If the key is not present in the map, the value of the variable is set to the empty sequence.

If $userinfo is non-empty and contains a non-empty password, then $userinfo is set to the empty sequence unless the allow-deprecated-features option is true.

If the omit-default-ports option is true then the $port is set to the empty sequence if the port number is the same as the default port for the given scheme. Implementations should recognize the default ports for http (80), https (443), ftp (21), and ssh (22). Exactly which ports are recognized is ·implementation-defined·.

If any of $userinfo, $host, or $port exist, the following authority is added to the URI under construction:

concat((if (exists($userinfo)) then $userinfo || "@" else ""), $host,
        (if (exists($port)) then ":" || $port else ""))

If none of userinfo, host, or port is present, and authority is present, the value of the authority key is added to the URI. (In this case, no attempt is made to determine if a password or standard port are present, the authority value is simply added to the string.)

If the path-segments key exists in the map, then the path is constructed from the parts, with non-URI characters encoded: string-join($parts?path-segments ! encode-for-uri(.), $options?path-separator), otherwise the value of the path key is used. If the path value is the empty sequence, the empty string is used for the path. The path is added to the URI.

If the query-parameters key exists in the map, its value must be a map. A sequence of strings is constructed from the values in the map. For each key and each value associated with that key in turn:

If the key is the empty string, the string constructed is the value encoded with encode-for-uri.
Otherwise, the string constructed is the value of the key, encoded, followed by an equal sign (=), followed by the value, encoded.

The query is constructed by joining the resulting strings into a single string, separated by $options?query-separator). If the query-parameters key does not exist in the map, but the query key does, then the query is the value of the query key. If there is a query, it is added to the URI with a preceding question mark (?).

If the fragment key exists in the map, then the value of that key is added to the URI with a preceding hash mark (#).

The resulting URI is returned.

Examples

Expression:	build-uri(map { "scheme": "https", "host": "qt4cg.org", "port": (), "path": "/specifications/index.html" })
Result:	"https://qt4cg.org/specifications/index.html"

History

7 Functions and operators on Boolean values

This section defines functions and operators on the xs:boolean datatype.

7.1 Boolean constant functions

Since no literals are defined in XPath to reference the constant boolean values true and false, two functions are provided for the purpose.

Function	Meaning
`fn:true`	Returns the `xs:boolean` value `true`.
`fn:false`	Returns the `xs:boolean` value `false`.

7.1.1 fn:true

Summary

Returns the xs:boolean value true.

Signature

fn:true() as xs:boolean

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The result is equivalent to xs:boolean("1").

Examples

Expression	Result
`true()`	xs:boolean(1)

7.1.2 fn:false

Summary

Returns the xs:boolean value false.

Signature

fn:false() as xs:boolean

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The result is equivalent to xs:boolean("0").

Examples

Expression	Result
`false()`	xs:boolean(0)

7.2 Operators on Boolean values

The following functions define the semantics of operators on boolean values in [XQuery 4.1: An XML Query Language] and [XML Path Language (XPath) 4.0]:

Function	Meaning
`op:boolean-equal`	Returns `true` if the two arguments are the same boolean value.
`op:boolean-less-than`	Returns `true` if the first argument is `false` and the second is `true`.

The ordering operator op:boolean-less-than is provided for application purposes and for compatibility with [XML Path Language (XPath) Version 1.0]. The [XML Schema Part 2: Datatypes Second Edition] datatype xs:boolean is not ordered.

7.2.1 op:boolean-equal

Summary

Returns true if the two arguments are the same boolean value.

Operator Mapping

Defines the semantics of the eq operator when applied to two xs:boolean values.

Signature

`op:boolean-equal`(
`$value1`	`as` `xs:boolean`,
`$value2`	`as` `xs:boolean`
) `as` `xs:boolean`

Rules

The function returns true if both arguments are true or if both arguments are false. It returns false if one of the arguments is true and the other argument is false.

7.2.2 op:boolean-less-than

Summary

Returns true if the first argument is false and the second is true.

Operator Mapping

Defines the semantics of the lt operator when applied to two xs:boolean values. Also used in the definition of the ge operator.

Signature

`op:boolean-less-than`(
`$arg1`	`as` `xs:boolean`,
`$arg2`	`as` `xs:boolean`
) `as` `xs:boolean`

Rules

The function returns true if $arg1 is false and $arg2 is true. Otherwise, it returns false.

7.3 Functions on Boolean values

The following functions are defined on boolean values:

Function	Meaning
`fn:boolean`	Computes the effective boolean value of the sequence `$input`.
`fn:not`	Returns `true` if the effective boolean value of `$input` is `false`, or `false` if it is `true`.

7.3.1 fn:boolean

Summary

Computes the effective boolean value of the sequence $input.

Signature

`fn:boolean`(
`$input`	`as` `item()*`
) `as` `xs:boolean`

Rules

The function computes the effective boolean value of a sequence, defined according to the following rules. See also Section 2.4.3 Effective Boolean Value ^XP31.

If $input is the empty sequence, fn:boolean returns false.
If $input is a sequence whose first item is a node, fn:boolean returns true.
If $input is a singleton value of type xs:boolean or a derived from xs:boolean, fn:boolean returns $input.
If $input is a singleton value of type xs:untypedAtomic, xs:string, xs:anyURI, or a type derived from xs:string or xs:anyURI, fn:boolean returns false if the operand value has zero length; otherwise it returns true.
If $input is a singleton value of any numeric type or a type derived from a numeric type, fn:boolean returns false if the operand value is NaN or is numerically equal to zero; otherwise it returns true.

Error Conditions

In all cases other than those listed above, fn:boolean raises a type error [err:FORG0006].

Notes

The result of this function is not necessarily the same as $input cast as xs:boolean. For example, fn:boolean("false") returns the value true whereas "false" cast as xs:boolean (which can also be written xs:boolean("false")) returns false.

Examples

Variables
let $abc := ("a", "b", "")

Expression	Result
`boolean($abc[1])`	true()
`boolean($abc[0])`	false()
`boolean($abc[3])`	false()
`fn:boolean($abc)` raises a type error [err:FORG0006].
`fn:boolean([])` raises a type error [err:FORG0006].

7.3.2 fn:not

Summary

Returns true if the effective boolean value of $input is false, or false if it is true.

Signature

`fn:not`(
`$input`	`as` `item()*`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The value of $input is first reduced to an effective boolean value by applying the fn:boolean() function. The function returns true if the effective boolean value is false, or false if the effective boolean value is true.

Examples

Expression	Result
`not(true())`	false()
`not(())`	true()
`not("false")`	false()
`fn:not(1 to 10)` raises a type error [err:FORG0006].

8 Functions and operators on durations

Operators are defined on the following type:

xs:duration

and on the two defined subtypes (see 8.1.1 Subtypes of duration):

xs:yearMonthDuration
xs:dayTimeDuration

No ordering relation is defined on xs:duration values. Two xs:duration values may however be compared for equality.

8.1 Duration data types

A value of type xs:duration is considered to comprise two parts:

The total number of months, represented as a signed integer.
The total number of seconds, represented as a signed decimal number.

If one of these values is negative (less than zero), the other must not be positive (greater than zero).

In effect this means that operations on durations (including equality comparison, casting to string, and extraction of components) all treat the duration as normalized. The duration PT1M30S (one minute and thirty seconds), for example, is precisely equivalent to the duration PT90S (ninety seconds); these are different representations of the same value, and the result of any operation will be the same regardless which representation is used. For example, the function fn:seconds-from-duration returns 30 in both cases.

Note:

The information content of an xs:duration value can be reduced to an xs:integer number of months, and an xs:decimal number of seconds. For the two defined subtypes this is further simplified so that one of these two components is fixed at zero. Operations such as comparison of durations and arithmetic on durations can be expressed in terms of numeric operations applied to these two components.

8.1.1 Subtypes of duration

Two subtypes of xs:duration, namely xs:yearMonthDuration and xs:dayTimeDuration, are defined in [Schema 1.1 Part 2]. These types must be available in the data model whether or not the implementation supports other aspects of XSD 1.1.

The significance of these subtypes is that arithmetic and ordering become well defined; this is not the case for xs:duration values in general, because of the variable number of days in a month. For this reason, many of the functions and operators on durations require the arguments/operands to belong to these two subtypes.

In an xs:yearMonthDuration, the seconds component is always zero. In an xs:dayTimeDuration, the months component is always zero.

8.1.2 Limits and precision

All minimally conforming processors must support duration values in which:

The total number of months can be represented as a signed xs:int value;
The total number of seconds can be represented as a signed xs:decimal value with facets totalDigits=18 and fractionalDigits=3. That is, durations must be supported to millisecond precision.

Processors may support a greater range and/or precision. The limits are ·implementation-defined·.

A processor that limits the range or precision of duration values may encounter overflow and underflow conditions when it tries to evaluate operations on durations. In these situations, the processor must return a zero-length duration in case of duration underflow, and must raise a dynamic error [err:FODT0001] in case of overflow.

8.2 Comparison operators on durations

Function	Meaning
`op:yearMonthDuration-less-than`	Returns `true` if `$arg1` is a shorter duration than `$arg2`.
`op:dayTimeDuration-less-than`	Returns `true` if `$arg1` is a shorter duration than `$arg2`.
`op:duration-equal`	Returns `true` if `$arg1` and `$arg2` are durations of the same length.

The following comparison operators are defined on the [XML Schema Part 2: Datatypes Second Edition] duration datatypes. Each operator takes two operands of the same type and returns an xs:boolean result. As discussed in [XML Schema Part 2: Datatypes Second Edition], the order relation on xs:duration is a partial order rather than a total order. For this reason, only equality is defined on xs:duration. A full complement of comparison and arithmetic functions are defined on the two subtypes of duration described in 8.1.1 Subtypes of duration which do have a total order.

8.2.1 op:yearMonthDuration-less-than

Summary

Returns true if $arg1 is a shorter duration than $arg2.

Operator Mapping

Defines the semantics of the lt operator when applied to two xs:yearMonthDuration values. Also used in the definition of the ge operator.

Signature

`op:yearMonthDuration-less-than`(
`$arg1`	`as` `xs:yearMonthDuration`,
`$arg2`	`as` `xs:yearMonthDuration`
) `as` `xs:boolean`

Rules

If the number of months in $arg1 is numerically less than the number of months in $arg2, the function returns true.

Otherwise, the function returns false.

Notes

Either or both durations may be negative.

8.2.2 op:dayTimeDuration-less-than

Summary

Returns true if $arg1 is a shorter duration than $arg2.

Operator Mapping

Defines the semantics of the lt operator when applied to two xs:dayTimeDuration values. Also used in the definition of the ge operator.

Signature

`op:dayTimeDuration-less-than`(
`$arg1`	`as` `xs:dayTimeDuration`,
`$arg2`	`as` `xs:dayTimeDuration`
) `as` `xs:boolean`

Rules

If the number of seconds in $arg1 is numerically less than the number of seconds in $arg2, the function returns true.

Otherwise, the function returns false.

Notes

Either or both durations may be negative

8.2.3 op:duration-equal

Summary

Returns true if $arg1 and $arg2 are durations of the same length.

Operator Mapping

Defines the semantics of the eq operators when applied to two xs:duration values. Also used in the definition of the ne operator.

Signature

`op:duration-equal`(
`$arg1`	`as` `xs:duration`,
`$arg2`	`as` `xs:duration`
) `as` `xs:boolean`

Rules

If the xs:yearMonthDuration components of $arg1 and $arg2 are equal and the xs:dayTimeDuration components of $arg1 and $arg2 are equal, the function returns true.

Otherwise, the function returns false.

The semantics of this function are:

xs:yearMonthDuration($arg1) div xs:yearMonthDuration('P1M')  eq
xs:yearMonthDuration($arg2) div xs:yearMonthDuration('P1M')
    and
xs:dayTimeDuration($arg1) div xs:dayTimeDuration('PT1S')  eq
xs:dayTimeDuration($arg2) div xs:dayTimeDuration('PT1S')

that is, the function returns true if the months and seconds values of the two durations are equal.

Notes

Note that this function, like any other, may be applied to arguments that are derived from the types given in the function signature, including the two subtypes xs:dayTimeDuration and xs:yearMonthDuration. With the exception of the zero-length duration, no instance of xs:dayTimeDuration can ever be equal to an instance of xs:yearMonthDuration.

Examples

Expression:	op:duration-equal( xs:duration("P1Y"), xs:duration("P12M") )
Result:	true()
Expression:	op:duration-equal( xs:duration("PT24H"), xs:duration("P1D") )
Result:	true()
Expression:	op:duration-equal( xs:duration("P1Y"), xs:duration("P365D") )
Result:	false()
Expression:	op:duration-equal( xs:yearMonthDuration("P0Y"), xs:dayTimeDuration("P0D") )
Result:	true()
Expression:	op:duration-equal( xs:yearMonthDuration("P1Y"), xs:dayTimeDuration("P365D") )
Result:	false()
Expression:	op:duration-equal( xs:yearMonthDuration("P2Y"), xs:yearMonthDuration("P24M") )
Result:	true()
Expression:	op:duration-equal( xs:dayTimeDuration("P10D"), xs:dayTimeDuration("PT240H") )
Result:	true()
Expression:	op:duration-equal( xs:duration("P2Y0M0DT0H0M0S"), xs:yearMonthDuration("P24M") )
Result:	true()
Expression:	op:duration-equal( xs:duration("P0Y0M10D"), xs:dayTimeDuration("PT240H") )
Result:	true()

8.3 Component extraction functions on durations

The duration datatype may be considered to be a composite datatype in that it contains distinct properties or components. The extraction functions specified below extract a single component from a duration value. For xs:duration and its subtypes, including the two subtypes xs:yearMonthDuration and xs:dayTimeDuration, the components are normalized: this means that the seconds and minutes components will always be less than 60, the hours component less than 24, and the months component less than 12.

Function	Meaning
`fn:years-from-duration`	Returns the number of years in a duration.
`fn:months-from-duration`	Returns the number of months in a duration.
`fn:days-from-duration`	Returns the number of days in a duration.
`fn:hours-from-duration`	Returns the number of hours in a duration.
`fn:minutes-from-duration`	Returns the number of minutes in a duration.
`fn:seconds-from-duration`	Returns the number of seconds in a duration.

8.3.1 fn:years-from-duration

Summary

Returns the number of years in a duration.

Signature

`fn:years-from-duration`(
`$value`	`as` `xs:duration?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer representing the years component in $value. Given that a duration is a ($months, $seconds) tuple, the result is the value of ($months idiv 12).

If $value is a negative duration then the result will be negative.

If $value is an xs:dayTimeDuration the function returns 0.

Examples

Expression:	years-from-duration( xs:yearMonthDuration("P20Y15M") )
Result:	21
Expression:	years-from-duration( xs:yearMonthDuration("-P15M") )
Result:	-1
Expression:	years-from-duration( xs:dayTimeDuration("-P2DT15H") )
Result:	0
Expression:	years-from-duration( xs:duration("P1Y1000D") )
Result:	1 (To capture whole portions of years reflected in the `xs:dayTimeDuration` component, it must first be converted to an `xs:yearMonthDuration`.)

8.3.2 fn:months-from-duration

Summary

Returns the number of months in a duration.

Signature

`fn:months-from-duration`(
`$value`	`as` `xs:duration?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer representing the months component in $value. Given that a duration is a ($months, $seconds) tuple, the result is the value of ($months mod 12).

If $value is a negative duration then the result will be negative.

If $value is an xs:dayTimeDuration the function returns 0.

Examples

Expression:	months-from-duration( xs:yearMonthDuration("P20Y15M") )
Result:	3
Expression:	months-from-duration( xs:yearMonthDuration("-P20Y18M") )
Result:	-6
Expression:	months-from-duration( xs:dayTimeDuration("-P2DT15H0M0S") )
Result:	0
Expression:	months-from-duration( xs:duration("P1M100D") )
Result:	1 (To capture whole portions of months reflected in the `xs:dayTimeDuration` component, it must first be converted to an `xs:yearMonthDuration`.)

8.3.3 fn:days-from-duration

Summary

Returns the number of days in a duration.

Signature

`fn:days-from-duration`(
`$value`	`as` `xs:duration?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer representing the days component in $value. Given that a duration is a ($months, $seconds) tuple, the result is ($seconds idiv 86400).

If $value is a negative duration then the result will be negative.

If $value is an xs:yearMonthDuration the function returns 0.

Examples

Expression:	days-from-duration( xs:dayTimeDuration("P3DT10H") )
Result:	3
Expression:	days-from-duration( xs:dayTimeDuration("P3DT55H") )
Result:	5
Expression:	days-from-duration( xs:yearMonthDuration("P3Y5M") )
Result:	0
Expression:	days-from-duration( xs:duration("P1Y1D") )
Result:	1 (To capture days reflected in the `xs:yearMonthDuration` component, it must first be converted to an `xs:dayTimeDuration`.)

8.3.4 fn:hours-from-duration

Summary

Returns the number of hours in a duration.

Signature

`fn:hours-from-duration`(
`$value`	`as` `xs:duration?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer representing the hours component in $value. Given that a duration is a ($months, $seconds) tuple, the result is the value of ($seconds mod 86400) idiv 3600.

If $value is a negative duration then the result will be negative.

If $value is an xs:yearMonthDuration the function returns 0.

Examples

Expression:	hours-from-duration( xs:dayTimeDuration("P3DT10H") )
Result:	10
Expression:	hours-from-duration( xs:dayTimeDuration("P3DT12H32M12S") )
Result:	12
Expression:	hours-from-duration( xs:dayTimeDuration("PT123H") )
Result:	3
Expression:	hours-from-duration( xs:dayTimeDuration("-P3DT10H") )
Result:	-10
Expression:	hours-from-duration( xs:duration("P1YT1H") )
Result:	1 (To capture hours reflected in the `xs:yearMonthDuration` component, it must first be converted to an `xs:dayTimeDuration`.)

8.3.5 fn:minutes-from-duration

Summary

Returns the number of minutes in a duration.

Signature

`fn:minutes-from-duration`(
`$value`	`as` `xs:duration?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer representing the minutes component in $value. Given that a duration is a ($months, $seconds) tuple, the result is the value of ($seconds mod 3600) idiv 60.

If $value is a negative duration then the result will be negative.

If $value is an xs:yearMonthDuration the function returns 0.

Examples

Expression:	minutes-from-duration( xs:dayTimeDuration("P3DT10H") )
Result:	0
Expression:	minutes-from-duration( xs:dayTimeDuration("-P5DT12H30M") )
Result:	-30
Expression:	minutes-from-duration( xs:duration("P1YT1M") )
Result:	1 (To capture minutes reflected in the `xs:yearMonthDuration` component, it must first be converted to an `xs:dayTimeDuration`.)

8.3.6 fn:seconds-from-duration

Summary

Returns the number of seconds in a duration.

Signature

`fn:seconds-from-duration`(
`$value`	`as` `xs:duration?`
) `as` `xs:decimal?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:decimal representing the seconds component in $value. Given that a duration is a ($months, $seconds) tuple, the result is the value of ($seconds mod 60) as an xs:decimal.

If $value is a negative duration then the result will be negative.

If $value is an xs:yearMonthDuration the function returns 0.

Examples

Expression:	seconds-from-duration( xs:dayTimeDuration("P3DT10H12.5S") )
Result:	12.5
Expression:	seconds-from-duration( xs:dayTimeDuration("-PT256S") )
Result:	-16.0
Expression:	seconds-from-duration( xs:duration("P1YT1S") )
Result:	1 (To capture seconds reflected in the `xs:yearMonthDuration` component of an `xs:duration`, it must first be converted to an `xs:dayTimeDuration`.)
Expression:	seconds-from-duration( xs:duration("P1YT1S") )
Result:	1 (To capture seconds reflected in the `xs:yearMonthDuration` component, it must first be converted to an `xs:dayTimeDuration`.)

8.4 Constructing durations

This section decribes the fn:seconds function, which constructs an xs:dayTimeDuration value representing a decimal number of seconds.

Function	Meaning
`fn:seconds`	Returns an `xs:dayTimeDuration` whose length is a given number of seconds.

8.4.1 fn:seconds

Summary

Returns an xs:dayTimeDuration whose length is a given number of seconds.

Signature

`fn:seconds`(
`$value`	`as` `xs:decimal?`
) `as` `xs:dayTimeDuration?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:dayTimeDuration value whose length in seconds is equal to $value.

If $value is negative then the result will be a negative duration.

For handling of overflow and underflow, see 9.7.1 Limits and precision.

Notes

The result of seconds($n) is approximately equal to the result of the expression xs:dayTimeDuration('PT1S') * $n. The equivalence is only approximate, because seconds($n) uses the exact xs:decimal value supplied, whereas multiplying a duration by a number first promotes the number to an xs:double value, which may lose precision.

Examples

Expression:	seconds(1)
Result:	xs:dayTimeDuration('PT1S')
Expression:	seconds(0.001)
Result:	xs:dayTimeDuration('PT0.001S')
Expression:	seconds(60)
Result:	xs:dayTimeDuration('PT1M')
Expression:	seconds(86400)
Result:	xs:dayTimeDuration('P1D')
Expression:	seconds(-5400)
Result:	xs:dayTimeDuration('-PT1H30M')
Expression:	xs:dateTime('1970-01-01T00:00:00Z') + 1706702400 * seconds(1)
Result:	xs:dateTime('2024-01-31T12:00:00Z') (The expression converts a Unix timestamp to an `xs:dateTime` value).
Expression:	(xs:dateTime('2024-01-31T12:00:00Z') - xs:dateTime('1970-01-01T00:00:00Z')) div seconds(1)
Result:	1706702400 (The expression converts an `xs:dateTime` value to a Unix timestamp).

8.5 Arithmetic operators on durations

Function	Meaning
`op:add-yearMonthDurations`	Returns the result of adding two `xs:yearMonthDuration` values.
`op:subtract-yearMonthDurations`	Returns the result of subtracting one `xs:yearMonthDuration` value from another.
`op:multiply-yearMonthDuration`	Returns the result of multiplying `$arg1` by `$arg2`. The result is rounded to the nearest month.
`op:divide-yearMonthDuration`	Returns the result of dividing `$arg1` by `$arg2`. The result is rounded to the nearest month.
`op:divide-yearMonthDuration-by-yearMonthDuration`	Returns the ratio of two `xs:yearMonthDuration` values.
`op:add-dayTimeDurations`	Returns the sum of two `xs:dayTimeDuration` values.
`op:subtract-dayTimeDurations`	Returns the result of subtracting one `xs:dayTimeDuration` from another.
`op:multiply-dayTimeDuration`	Returns the result of multiplying a `xs:dayTimeDuration` by a number.
`op:divide-dayTimeDuration`	Returns the result of multiplying a `xs:dayTimeDuration` by a number.
`op:divide-dayTimeDuration-by-dayTimeDuration`	Returns the ratio of two `xs:dayTimeDuration` values, as a decimal number.

For operators that combine a duration and a date/time value, see 9.7 Arithmetic operators on durations, dates and times.

8.5.1 op:add-yearMonthDurations

Summary

Returns the result of adding two xs:yearMonthDuration values.

Operator Mapping

Defines the semantics of the + operator when applied to two xs:yearMonthDuration values.

Signature

`op:add-yearMonthDurations`(
`$arg1`	`as` `xs:yearMonthDuration`,
`$arg2`	`as` `xs:yearMonthDuration`
) `as` `xs:yearMonthDuration`

Rules

The function returns the result of adding $arg1 to $arg2. The result will be an xs:yearMonthDuration whose length in months is equal to the length in months of $arg1 plus the length in months of $arg2.

For handling of overflow, see 9.7.1 Limits and precision.

Notes

Either duration (and therefore the result) may be negative.

Examples

Expression:	op:add-yearMonthDurations( xs:yearMonthDuration("P2Y11M"), xs:yearMonthDuration("P3Y3M") )
Result:	xs:yearMonthDuration("P6Y2M")

8.5.2 op:subtract-yearMonthDurations

Summary

Returns the result of subtracting one xs:yearMonthDuration value from another.

Operator Mapping

Defines the semantics of the - operator when applied to two xs:yearMonthDuration values.

Signature

`op:subtract-yearMonthDurations`(
`$arg1`	`as` `xs:yearMonthDuration`,
`$arg2`	`as` `xs:yearMonthDuration`
) `as` `xs:yearMonthDuration`

Rules

The function returns the result of subtracting $arg2 from $arg1. The result will be an xs:yearMonthDuration whose length in months is equal to the length in months of $arg1 minus the length in months of $arg2.

For handling of overflow, see 9.7.1 Limits and precision.

Notes

Either duration (and therefore the result) may be negative.

Examples

Expression:	op:subtract-yearMonthDurations( xs:yearMonthDuration("P2Y11M"), xs:yearMonthDuration("P3Y3M") )
Result:	xs:yearMonthDuration("-P4M")

8.5.3 op:multiply-yearMonthDuration

Summary

Returns the result of multiplying $arg1 by $arg2. The result is rounded to the nearest month.

Operator Mapping

Defines the semantics of the * operator when applied to an xs:yearMonthDuration and a numeric value.

Signature

`op:multiply-yearMonthDuration`(
`$arg1`	`as` `xs:yearMonthDuration`,
`$arg2`	`as` `xs:double`
) `as` `xs:yearMonthDuration`

Rules

The result is the xs:yearMonthDuration whose length in months is equal to the result of applying the fn:round function to the value obtained by multiplying the length in months of $arg1 by the value of $arg2.

If $arg2 is positive or negative zero, the result is a zero-length duration. If $arg2 is positive or negative infinity, the result overflows and is handled as described in 9.7.1 Limits and precision.

For handling of overflow and underflow, see 9.7.1 Limits and precision.

Error Conditions

A dynamic error is raised [err:FOCA0005] if $arg2 is NaN.

Notes

Either duration (and therefore the result) may be negative.

Examples

Expression:	op:multiply-yearMonthDuration( xs:yearMonthDuration("P2Y11M"), 2.3 )
Result:	xs:yearMonthDuration("P6Y9M")

8.5.4 op:divide-yearMonthDuration

Summary

Returns the result of dividing $arg1 by $arg2. The result is rounded to the nearest month.

Operator Mapping

Defines the semantics of the div operator when applied to an xs:yearMonthDuration and a numeric value.

Signature

`op:divide-yearMonthDuration`(
`$arg1`	`as` `xs:yearMonthDuration`,
`$arg2`	`as` `xs:double`
) `as` `xs:yearMonthDuration`

Rules

The result is the xs:yearMonthDuration whose length in months is equal to the result of applying the fn:round function to the value obtained by dividing the length in months of $arg1 by the value of $arg2.

If $arg2 is positive or negative infinity, the result is a zero-length duration. If $arg2 is positive or negative zero, the result overflows and is handled as described in 9.7.1 Limits and precision.

For handling of overflow and underflow, see 9.7.1 Limits and precision.

Error Conditions

A dynamic error is raised [err:FOCA0005] if $arg2 is NaN.

Notes

Either operand (and therefore the result) may be negative.

Examples

Expression:	op:divide-yearMonthDuration( xs:yearMonthDuration("P2Y11M"), 1.5 )
Result:	xs:yearMonthDuration("P1Y11M")

8.5.5 op:divide-yearMonthDuration-by-yearMonthDuration

Summary

Returns the ratio of two xs:yearMonthDuration values.

Operator Mapping

Defines the semantics of the div operator when applied to two xs:yearMonthDuration values.

Signature

`op:divide-yearMonthDuration-by-yearMonthDuration`(
`$arg1`	`as` `xs:yearMonthDuration`,
`$arg2`	`as` `xs:yearMonthDuration`
) `as` `xs:decimal`

Rules

The function returns the result of dividing the length in months of $arg1 by the length in months of $arg2, according to the rules of the op:numeric-divide function for integer operands.

For handling of overflow and underflow, see 9.7.1 Limits and precision.

Notes

Either duration (and therefore the result) may be negative.

Examples

Expression:	op:divide-yearMonthDuration-by-yearMonthDuration( xs:yearMonthDuration("P3Y4M"), xs:yearMonthDuration("-P1Y4M") )
Result:	-2.5
The following example demonstrates how to calculate the length of an `xs:yearMonthDuration` value in months:
Expression:	op:divide-yearMonthDuration-by-yearMonthDuration( xs:yearMonthDuration("P3Y4M"), xs:yearMonthDuration("P1M") )
Result:	40

8.5.6 op:add-dayTimeDurations

Summary

Returns the sum of two xs:dayTimeDuration values.

Operator Mapping

Defines the semantics of the + operator when applied to two xs:dayTimeDuration values.

Signature

`op:add-dayTimeDurations`(
`$arg1`	`as` `xs:dayTimeDuration`,
`$arg2`	`as` `xs:dayTimeDuration`
) `as` `xs:dayTimeDuration`

Rules

The function returns the result of adding $arg1 to $arg2. The result is the xs:dayTimeDuration whose length in seconds is equal to the sum of the length in seconds of the two input durations.

For handling of overflow, see 9.7.1 Limits and precision.

Notes

Either duration (and therefore the result) may be negative.

Examples

Expression:	op:add-dayTimeDurations( xs:dayTimeDuration("P2DT12H5M"), xs:dayTimeDuration("P5DT12H") )
Result:	xs:dayTimeDuration('P8DT5M')

8.5.7 op:subtract-dayTimeDurations

Summary

Returns the result of subtracting one xs:dayTimeDuration from another.

Operator Mapping

Defines the semantics of the - operator when applied to two xs:dayTimeDuration values.

Signature

`op:subtract-dayTimeDurations`(
`$arg1`	`as` `xs:dayTimeDuration`,
`$arg2`	`as` `xs:dayTimeDuration`
) `as` `xs:dayTimeDuration`

Rules

The function returns the result of subtracting $arg2 from $arg1. The result is the xs:dayTimeDuration whose length in seconds is equal to the length in seconds of $arg1 minus the length in seconds of $arg2.

For handling of overflow, see 9.7.1 Limits and precision.

Notes

Either duration (and therefore the result) may be negative.

Examples

Expression:	op:subtract-dayTimeDurations( xs:dayTimeDuration("P2DT12H"), xs:dayTimeDuration("P1DT10H30M") )
Result:	xs:dayTimeDuration('P1DT1H30M')

8.5.8 op:multiply-dayTimeDuration

Summary

Returns the result of multiplying a xs:dayTimeDuration by a number.

Operator Mapping

Defines the semantics of the * operator when applied to an xs:dayTimeDuration and a numeric value.

Signature

`op:multiply-dayTimeDuration`(
`$arg1`	`as` `xs:dayTimeDuration`,
`$arg2`	`as` `xs:double`
) `as` `xs:dayTimeDuration`

Rules

The function returns the result of multiplying $arg1 by $arg2. The result is the xs:dayTimeDuration whose length in seconds is equal to the length in seconds of $arg1 multiplied by the numeric value $arg2.

For handling of overflow and underflow, see 9.7.1 Limits and precision.

Error Conditions

A dynamic error is raised [err:FOCA0005] if $arg2 is NaN.

Notes

Either operand (and therefore the result) may be negative.

Examples

Expression:	op:multiply-dayTimeDuration( xs:dayTimeDuration("PT2H10M"), 2.1 )
Result:	xs:dayTimeDuration('PT4H33M')

8.5.9 op:divide-dayTimeDuration

Summary

Returns the result of multiplying a xs:dayTimeDuration by a number.

Operator Mapping

Defines the semantics of the div operator when applied to two xs:dayTimeDuration values.

Signature

`op:divide-dayTimeDuration`(
`$arg1`	`as` `xs:dayTimeDuration`,
`$arg2`	`as` `xs:double`
) `as` `xs:dayTimeDuration`

Rules

For handling of overflow and underflow, see 9.7.1 Limits and precision.

Error Conditions

A dynamic error is raised [err:FOCA0005] if $arg2 is NaN.

Notes

Either operand (and therefore the result) may be negative.

Examples

Expression:	op:divide-dayTimeDuration( xs:dayTimeDuration("P1DT2H30M10.5S"), 1.5 )
Result:	xs:duration("PT17H40M7S")

8.5.10 op:divide-dayTimeDuration-by-dayTimeDuration

Summary

Returns the ratio of two xs:dayTimeDuration values, as a decimal number.

Operator Mapping

Defines the semantics of the div operator when applied to two xs:dayTimeDuration values.

Signature

`op:divide-dayTimeDuration-by-dayTimeDuration`(
`$arg1`	`as` `xs:dayTimeDuration`,
`$arg2`	`as` `xs:dayTimeDuration`
) `as` `xs:decimal`

Rules

The function returns the result of dividing $arg1 by $arg2. The result is the xs:dayTimeDuration whose length in seconds is equal to the length in seconds of $arg1 divided by the length in seconds of $arg2. The calculation is performed by applying op:numeric-divide to the two xs:decimal operands.

For handling of overflow and underflow, see 9.7.1 Limits and precision.

Notes

Either operand (and therefore the result) may be negative.

Examples

Expression:	round-half-to-even( op:divide-dayTimeDuration-by-dayTimeDuration( xs:dayTimeDuration("P2DT53M11S"), xs:dayTimeDuration("P1DT10H") ), 4 )
Result:	1.4378
This examples shows how to determine the number of seconds in a duration.
Expression:	op:divide-dayTimeDuration-by-dayTimeDuration( xs:dayTimeDuration("P2DT53M11S"), xs:dayTimeDuration("PT1S") )
Result:	175991.0

9 Functions and operators on dates and times

This section defines operations on the [XML Schema Part 2: Datatypes Second Edition] date and time types.

See [Working With Timezones] for a disquisition on working with date and time values with and without timezones.

9.1 Date and time types

The operators described in this section are defined on the following date and time types:

xs:dateTime
xs:date
xs:time
xs:gYearMonth
xs:gYear
xs:gMonthDay
xs:gMonth
xs:gDay

The only operation defined on xs:gYearMonth, xs:gYear, xs:gMonthDay, xs:gMonth and xs:gDay values is equality comparison. For other types, further operations are provided, including component extraction, order comparisons, arithmetic, formatted display, and timezone adjustment.

9.1.1 Limits and precision

All minimally conforming processors must support positive year values with a minimum of 4 digits (i.e., YYYY) and a minimum fractional second precision of 1 millisecond or three digits (i.e., s.sss). However, conforming processors may set larger ·implementation-defined· limits on the maximum number of digits they support in these two situations. Processors may also choose to support the year 0 and years with negative values. The results of operations on dates that cross the year 0 are ·implementation-defined·.

A processor that limits the number of digits in date and time datatype representations may encounter overflow and underflow conditions when it tries to execute the functions in 9.7 Arithmetic operators on durations, dates and times. In these situations, the processor must return 00:00:00 in case of time underflow. It must raise a dynamic error [err:FODT0001] in case of overflow.

9.2 Date/time datatype values

As defined in Section 3.3.2 Dates and Times ^DM31, xs:dateTime, xs:date, xs:time, xs:gYearMonth, xs:gYear, xs:gMonthDay, xs:gMonth, xs:gDay values, referred to collectively as date/time values, are represented as seven components or properties: year, month, day, hour, minute, second and timezone. The first five components are xs:integer values. The value of the second component is an xs:decimal and the value of the timezone component is an xs:dayTimeDuration. For all the primitive date/time datatypes, the timezone property is optional and may or may not be present. Depending on the datatype, some of the remaining six properties must be present and some must be absent^DM31. Absent, or missing, properties are represented by the empty sequence. This value is referred to as the local value in that the value retains its original timezone. Before comparing or subtracting xs:dateTime values, this local value must be translated or normalized to UTC.

For xs:time, 00:00:00 and 24:00:00 are alternate lexical forms for the same value, whose canonical representation is 00:00:00. For xs:dateTime, a time component 24:00:00 translates to 00:00:00 of the following day.

9.2.1 Examples

An xs:dateTime with lexical representation 1999-05-31T05:00:00 is represented in the datamodel by {1999, 5, 31, 5, 0, 0.0, ()}.
An xs:dateTime with lexical representation 1999-05-31T13:20:00-05:00 is represented by {1999, 5, 31, 13, 20, 0.0, xs:dayTimeDuration("-PT5H")}.
An xs:dateTime with lexical representation 1999-12-31T24:00:00 is represented by {2000, 1, 1, 0, 0, 0.0, ()}.
An xs:date with lexical representation 2005-02-28+8:00 is represented by {2005, 2, 28, (), (), (), xs:dayTimeDuration("PT8H")}.
An xs:time with lexical representation 24:00:00 is represented by {(), (), (), 0, 0, 0, ()}.

9.3 Constructing a dateTime

A function is provided for constructing a xs:dateTime value from a xs:date value and a xs:time value.

Function	Meaning
`fn:dateTime`	Returns an `xs:dateTime` value created by combining an `xs:date` and an `xs:time`.

9.3.1 fn:dateTime

Summary

Returns an xs:dateTime value created by combining an xs:date and an xs:time.

Signature

`fn:dateTime`(
`$date`	`as` `xs:date?`,
`$time`	`as` `xs:time?`
) `as` `xs:dateTime?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If either $date or $time is the empty sequence the function returns the empty sequence.

Otherwise, the function returns an xs:dateTime whose date component is equal to $date and whose time component is equal to $time.

The timezone of the result is computed as follows:

If neither argument has a timezone, the result has no timezone.
If exactly one of the arguments has a timezone, or if both arguments have the same timezone, the result has this timezone.

Error Conditions

A dynamic error is raised [err:FORG0008] if the two arguments both have timezones and the timezones are different.

Examples

Expression	Result
dateTime( xs:date("1999-12-31"), xs:time("12:00:00") )	xs:dateTime("1999-12-31T12:00:00")
dateTime( xs:date("1999-12-31"), xs:time("24:00:00") )	xs:dateTime("1999-12-31T00:00:00") (This is because `"24:00:00"` is an alternate lexical form for `"00:00:00"`).

9.4 Comparison operators on duration, date and time values

Function	Meaning
`op:dateTime-equal`	Returns `true` if the two supplied `xs:dateTime` values refer to the same instant in time.
`op:dateTime-less-than`	Returns `true` if the first argument represents an earlier instant in time than the second argument.
`op:date-equal`	Returns `true` if and only if the starting instants of the two supplied `xs:date` values are the same.
`op:date-less-than`	Returns `true` if and only if the starting instant of `$arg1` is less than the starting instant of `$arg2`. Returns `false` otherwise.
`op:time-equal`	Returns `true` if the two `xs:time` values represent the same instant in time, when treated as being times on the same date, before adjusting the timezone.
`op:time-less-than`	Returns `true` if the first `xs:time` value represents an earlier instant in time than the second, when both are treated as being times on the same date, before adjusting the timezone.
`op:gYearMonth-equal`	Returns `true` if the two `xs:gYearMonth` values have the same starting instant.
`op:gYear-equal`	Returns `true` if the two `xs:gYear` values have the same starting instant.
`op:gMonthDay-equal`	Returns `true` if the two `xs:gMonthDay` values have the same starting instant, when considered as days in the same year.
`op:gMonth-equal`	Returns `true` if the two `xs:gMonth` values have the same starting instant, when considered as months in the same year.
`op:gDay-equal`	Returns `true` if the two `xs:gDay` values have the same starting instant, when considered as days in the same month of the same year.

The following comparison operators are defined on the [XML Schema Part 2: Datatypes Second Edition] date/time datatypes. Each operator takes two operands of the same type and returns an xs:boolean result.

[XML Schema Part 2: Datatypes Second Edition] also states that the order relation on date and time datatypes is not a total order but a partial order because these datatypes may or may not have a timezone. This is handled as follows. If either operand to a comparison function on date or time values does not have an (explicit) timezone then, for the purpose of the operation, an implicit timezone, provided by the dynamic context Section C.2 Dynamic Context Components ^XP31, is assumed to be present as part of the value. This creates a total order for all date and time values.

An xs:dateTime can be considered to consist of seven components: year, month, day, hour, minute, second and timezone. For xs:dateTime six components (year, month, day, hour, minute and second) are required and timezone is optional. For other date/time values, of the first six components, some are required and others must be absent^DM31. Timezone is always optional. For example, for xs:date, the year, month and day components are required and hour, minute and second components must be absent; for xs:time the hour, minute and second components are required and year, month and day are missing; for xs:gDay, day is required and year, month, hour, minute and second are missing.

Note:

In [Schema 1.1 Part 2], a new explicitTimezone facet is available with values optional, required, or prohibited to enable the timezone to be defined as mandatory or disallowed.

Values of the date/time datatypes xs:time, xs:gMonthDay, xs:gMonth, and xs:gDay, can be considered to represent a sequence of recurring time instants or time periods. An xs:time occurs every day. An xs:gMonth occurs every year. Comparison operators on these datatypes compare the starting instants of equivalent occurrences in the recurring series. These xs:dateTime values are calculated as described below.

Comparison operators on xs:date, xs:gYearMonth and xs:gYear compare their starting instants. These xs:dateTime values are calculated as described below.

The starting instant of an occurrence of a date/time value is an xs:dateTime calculated by filling in the missing components of the local value from a reference xs:dateTime. An example of a suitable reference xs:dateTime is 1972-01-01T00:00:00. Then, for example, the starting instant corresponding to the xs:date value 2009-03-12 is 2009-03-12T00:00:00; the starting instant corresponding to the xs:time value 13:30:02 is 1972-01-01T13:30:02; and the starting instant corresponding to the gMonthDay value --02-29 is 1972-02-29T00:00:00 (which explains why a leap year was chosen for the reference).

Note:

In the previous version of this specification, the reference date/time chosen was 1972-12-31T00:00:00. While this gives the same results, it produces a "starting instant" for a gMonth or gMonthDay that bears no relation to the ordinary meaning of the term, and it also required special handling of short months. The original choice was made to allow for leap seconds; but since leap seconds are not recognized in date/time arithmetic, this is not actually necessary.

If the xs:time value written as 24:00:00 is to be compared, filling in the missing components gives 1972-01-01T00:00:00, because 24:00:00 is an alternative representation of 00:00:00 (the lexical value "24:00:00" is converted to the time components {0,0,0} before the missing components are filled in). This has the consequence that when ordering xs:time values, 24:00:00 is considered to be earlier than 23:59:59. However, when ordering xs:dateTime values, a time component of 24:00:00 is considered equivalent to 00:00:00 on the following day.

Note that the reference xs:dateTime does not have a timezone. The timezone component is never filled in from the reference xs:dateTime. In some cases, if the date/time value does not have a timezone, the implicit timezone from the dynamic context is used as the timezone.

Note:

This specification uses the reference xs:dateTime 1972-01-01T00:00:00 in the description of the comparison operators. Implementations may use other reference xs:dateTime values as long as they yield the same results. The reference xs:dateTime used must meet the following constraints: when it is used to supply components into xs:gMonthDay values, the year must allow for February 29 and so must be a leap year; when it is used to supply missing components into xs:gDay values, the month must allow for 31 days. Different reference xs:dateTime values may be used for different operators.

9.4.1 op:dateTime-equal

Summary

Returns true if the two supplied xs:dateTime values refer to the same instant in time.

Operator Mapping

Defines the semantics of the eq operator when applied to two xs:dateTime values. Also used in the definition of the ne, le and ge operators.

Signature

`op:dateTime-equal`(
`$arg1`	`as` `xs:dateTime`,
`$arg2`	`as` `xs:dateTime`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

If either $arg1 or $arg2 has no timezone component, the effective value of the argument is obtained by substituting the implicit timezone from the dynamic evaluation context.

The function then returns true if and only if the effective value of $arg1 is equal to the effective value of $arg2 according to the algorithm defined in section 3.2.7.4 of [XML Schema Part 2: Datatypes Second Edition] “Order relation on dateTime” for xs:dateTime values with timezones. Otherwise the function returns false.

Examples

Assume that the dynamic context provides an implicit timezone value of `-05:00`
Expression:	op:dateTime-equal( xs:dateTime("2002-04-02T12:00:00-01:00"), xs:dateTime("2002-04-02T17:00:00+04:00") )
Result:	true()
Expression:	op:dateTime-equal( xs:dateTime("2002-04-02T12:00:00"), xs:dateTime("2002-04-02T23:00:00+06:00") )
Result:	true()
Expression:	op:dateTime-equal( xs:dateTime("2002-04-02T12:00:00"), xs:dateTime("2002-04-02T17:00:00") )
Result:	false()
Expression:	op:dateTime-equal( xs:dateTime("2002-04-02T12:00:00"), xs:dateTime("2002-04-02T12:00:00") )
Result:	true()
Expression:	op:dateTime-equal( xs:dateTime("2002-04-02T23:00:00-04:00"), xs:dateTime("2002-04-03T02:00:00-01:00") )
Result:	true()
Expression:	op:dateTime-equal( xs:dateTime("1999-12-31T24:00:00"), xs:dateTime("2000-01-01T00:00:00") )
Result:	true()
Expression:	op:dateTime-equal( xs:dateTime("2005-04-04T24:00:00"), xs:dateTime("2005-04-04T00:00:00") )
Result:	false()

9.4.2 op:dateTime-less-than

Summary

Returns true if the first argument represents an earlier instant in time than the second argument.

Operator Mapping

Defines the semantics of the lt operator when applied to two xs:dateTime values. Also used in the definition of the ge operator.

Signature

`op:dateTime-less-than`(
`$arg1`	`as` `xs:dateTime`,
`$arg2`	`as` `xs:dateTime`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

If either $arg1 or $arg2 has no timezone component, the effective value of the argument is obtained by substituting the implicit timezone from the dynamic evaluation context.

The function then returns true if and only if the effective value of $arg1 is less than the effective value of $arg2 according to the algorithm defined in section 3.2.7.4 of [XML Schema Part 2: Datatypes Second Edition] “Order relation on dateTime” for xs:dateTime values with timezones. Otherwise the function returns false.

9.4.3 op:date-equal

Summary

Returns true if and only if the starting instants of the two supplied xs:date values are the same.

Operator Mapping

Defines the semantics of the eq operator when applied to two xs:date values. Also used in the definition of the ne, le and ge operators.

Signature

`op:date-equal`(
`$arg1`	`as` `xs:date`,
`$arg2`	`as` `xs:date`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

The starting instant of an xs:date is the xs:dateTime at time 00:00:00 on that date.

The function returns the result of the expression:

op:dateTime-equal(xs:dateTime($arg1), xs:dateTime($arg2))

Examples

Expression	Result
op:date-equal( xs:date("2004-12-25Z"), xs:date("2004-12-25+07:00") )	false() (The starting instants are `xs:dateTime("2004-12-25T00:00:00Z")` and `xs:dateTime("2004-12-25T00:00:00+07:00")`. These are normalized to `xs:dateTime("2004-12-25T00:00:00Z")` and `xs:dateTime("2004-12-24T17:00:00Z")`. ).
op:date-equal( xs:date("2004-12-25-12:00"), xs:date("2004-12-26+12:00") )	true()

9.4.4 op:date-less-than

Summary

Returns true if and only if the starting instant of $arg1 is less than the starting instant of $arg2. Returns false otherwise.

Operator Mapping

Defines the semantics of the lt operator when applied to two xs:date values. Also used in the definition of the ge operator.

Signature

`op:date-less-than`(
`$arg1`	`as` `xs:date`,
`$arg2`	`as` `xs:date`
) `as` `xs:boolean`

Rules

The starting instant of an xs:date is the xs:dateTime at time 00:00:00 on that date.

The function returns the result of the expression:

op:dateTime-less-than(xs:dateTime($arg1), xs:dateTime($arg2))

Examples

Expression	Result
op:date-less-than( xs:date("2004-12-25Z"), xs:date("2004-12-25-05:00") )	true()
op:date-less-than( xs:date("2004-12-25-12:00"), xs:date("2004-12-26+12:00") )	false()

9.4.5 op:time-equal

Summary

Returns true if the two xs:time values represent the same instant in time, when treated as being times on the same date, before adjusting the timezone.

Operator Mapping

Defines the semantics of the eq operator when applied to two xs:time values. Also used in the definition of the ne, le and ge operators.

Signature

`op:time-equal`(
`$arg1`	`as` `xs:time`,
`$arg2`	`as` `xs:time`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

Each of the supplied xs:time values is expanded to an xs:dateTime value by associating the time with an arbitrary date. The function returns the result of comparing these two xs:dateTime values using op:dateTime-equal.

The result of the function is thus the same as the value of the expression:

op:dateTime-equal(
        dateTime(xs:date('1972-12-31'), $arg1), 
        dateTime(xs:date('1972-12-31'), $arg2))

Examples

Expression	Result
Assume that the date components from the reference `xs:dateTime` correspond to `1972-12-31`.
op:time-equal( xs:time("08:00:00+09:00"), xs:time("17:00:00-06:00") )	false() (Using the reference date components the starting instants are `1972-12-31T08:00:00+09:00` and `1972-12-31T17:00:00-06:00`, respectively, and normalize to `1972-12-30T23:00:00Z` and `1972-12-31T23:00:00Z`. ).
op:time-equal( xs:time("21:30:00+10:30"), xs:time("06:00:00-05:00") )	true()
op:time-equal( xs:time("24:00:00+01:00"), xs:time("00:00:00+01:00") )	true() (This not the result one might expect. For `xs:dateTime` values, a time of `24:00:00` is equivalent to `00:00:00` on the following day. For `xs:time`, the normalization from `24:00:00` to `00:00:00` happens before the `xs:time` is converted into an `xs:dateTime` for the purpose of the equality comparison. For `xs:time`, any operation on `24:00:00` produces the same result as the same operation on `00:00:00` because these are two different lexical representations of the same value. ).

9.4.6 op:time-less-than

Summary

Returns true if the first xs:time value represents an earlier instant in time than the second, when both are treated as being times on the same date, before adjusting the timezone.

Operator Mapping

Defines the semantics of the lt operator when applied to two xs:time values. Also used in the definition of the ge operator.

Signature

`op:time-less-than`(
`$arg1`	`as` `xs:time`,
`$arg2`	`as` `xs:time`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

The result of the function is thus the same as the value of the expression:

op:dateTime-less-than(
        dateTime(xs:date('1972-12-31'), $arg1), 
        dateTime(xs:date('1972-12-31'), $arg2))

Examples

Expression	Result
Assume that the dynamic context provides an implicit timezone value of `-05:00`.
op:time-less-than( xs:time("12:00:00"), xs:time("23:00:00+06:00") )	false()
op:time-less-than( xs:time("11:00:00"), xs:time("17:00:00Z") )	true()
op:time-less-than( xs:time("23:59:59"), xs:time("24:00:00") )	false()

9.4.7 op:gYearMonth-equal

Summary

Returns true if the two xs:gYearMonth values have the same starting instant.

Operator Mapping

Defines the semantics of the eq operator when applied to two xs:gYearMonth values. Also used in the definition of the ne operator.

Signature

`op:gYearMonth-equal`(
`$arg1`	`as` `xs:gYearMonth`,
`$arg2`	`as` `xs:gYearMonth`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

The starting instants of $arg1 and $arg2 are calculated by supplying the missing components of $arg1 and $arg2 from the xs:dateTime template xxxx-xx-01T00:00:00. The function returns the result of comparing these two starting instants using op:dateTime-equal.

Examples

Assume that the dynamic context provides an implicit timezone value of `-05:00`.
`op:gYearMonth-equal(xs:gYearMonth("1986-02"), xs:gYearMonth("1986-03"))` returns `false()`. The starting instants are `1986-02-01T00:00:00-05:00` and `1986-03-01T00:00:00`, respectively.
`op:gYearMonth-equal(xs:gYearMonth("1978-03"), xs:gYearMonth("1986-03Z"))` returns `false()`. The starting instants are `1978-03-01T00:00:00-05:00` and `1986-03-01T00:00:00Z`, respectively.

9.4.8 op:gYear-equal

Summary

Returns true if the two xs:gYear values have the same starting instant.

Operator Mapping

Defines the semantics of the eq operator when applied to two xs:gYear values. Also used in the definition of the ne operator.

Signature

`op:gYear-equal`(
`$arg1`	`as` `xs:gYear`,
`$arg2`	`as` `xs:gYear`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

The starting instants of $arg1 and $arg2 are calculated by supplying the missing components of $arg1 and $arg2 from the xs:dateTime template xxxx-01-01T00:00:00. The function returns the result of comparing these two starting instants using op:dateTime-equal.

Examples

Expression	Result
Assume that the dynamic context provides an implicit timezone value of `-05:00`. Assume, also, that the `xs:dateTime` template is `xxxx-01-01T00:00:00`.
`op:gYear-equal(xs:gYear("2005-12:00"), xs:gYear("2005+12:00"))` returns `false()`. The starting instants are `2005-01-01T00:00:00-12:00` and `2005-01-01T00:00:00+12:00`, respectively, and normalize to `2005-01-01T12:00:00Z` and `2004-12-31T12:00:00Z`.
op:gYear-equal( xs:gYear("1976-05:00"), xs:gYear("1976") )	true()

9.4.9 op:gMonthDay-equal

Summary

Returns true if the two xs:gMonthDay values have the same starting instant, when considered as days in the same year.

Operator Mapping

Defines the semantics of the eq operator when applied to two xs:gMonthDay values. Also used in the definition of the ne operator.

Signature

`op:gMonthDay-equal`(
`$arg1`	`as` `xs:gMonthDay`,
`$arg2`	`as` `xs:gMonthDay`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

The starting instants of $arg1 and $arg2 are calculated by supplying the missing components of $arg1 and $arg2 from the xs:dateTime template 1972-xx-xxT00:00:00 or an equivalent. The function returns the result of comparing these two starting instants using op:dateTime-equal.

Examples

Assume that the dynamic context provides an implicit timezone value of `-05:00`. Assume for the purposes of illustration that the `xs:dateTime` template used is `1972-xx-xxT00:00:00` (this does not affect the result).
Expression:	op:gMonthDay-equal( xs:gMonthDay("--12-25-14:00"), xs:gMonthDay("--12-26+10:00") )
Result:	true() ( The starting instants are `1972-12-25T00:00:00-14:00` and `1972-12-26T00:00:00+10:00`, respectively, and normalize to `1972-12-25T14:00:00Z` and `1972-12-25T14:00:00Z`. ).
Expression:	op:gMonthDay-equal( xs:gMonthDay("--12-25"), xs:gMonthDay("--12-26Z") )
Result:	false()

9.4.10 op:gMonth-equal

Summary

Returns true if the two xs:gMonth values have the same starting instant, when considered as months in the same year.

Operator Mapping

Defines the semantics of the eq operator when applied to two xs:gMonth values. Also used in the definition of the ne operator.

Signature

`op:gMonth-equal`(
`$arg1`	`as` `xs:gMonth`,
`$arg2`	`as` `xs:gMonth`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

The starting instants of $arg1 and $arg2 are calculated by supplying the missing components of $arg1 and $arg2 from the xs:dateTime template 1972-xx-01T00:00:00 or an equivalent. The function returns the result of comparing these two starting instants using op:dateTime-equal.

Examples

Expression	Result
Assume that the dynamic context provides an implicit timezone value of `-05:00`. Assume, also, that the `xs:dateTime` template chosen is `1972-xx-01T00:00:00`.
op:gMonth-equal( xs:gMonth("--12-14:00"), xs:gMonth("--12+10:00") )	false() ( The starting instants are `1972-12-01T00:00:00-14:00` and `1972-12-01T00:00:00+10:00`, respectively, and normalize to `1972-11-30T14:00:00Z` and `1972-12-01T14:00:00Z`. ).
op:gMonth-equal( xs:gMonth("--12"), xs:gMonth("--12Z") )	false()

9.4.11 op:gDay-equal

Summary

Returns true if the two xs:gDay values have the same starting instant, when considered as days in the same month of the same year.

Operator Mapping

Defines the semantics of the eq operator when applied to two xs:gDay values. Also used in the definition of the ne operator.

Signature

`op:gDay-equal`(
`$arg1`	`as` `xs:gDay`,
`$arg2`	`as` `xs:gDay`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

The starting instants of $arg1 and $arg2 are calculated by supplying the missing components of $arg1 and $arg2 from the xs:dateTime template 1972-12-xxT00:00:00 or an equivalent. The function returns the result of comparing these two starting instants using op:dateTime-equal.

Examples

Expression	Result
Assume that the dynamic context provides an implicit timezone value of `-05:00`. Assume, also, that the `xs:dateTime` template is `1972-12-xxT00:00:00`.
op:gDay-equal( xs:gDay("---25-14:00"), xs:gDay("---25+10:00") )	false() ( The starting instants are `1972-12-25T00:00:00-14:00` and `1972-12-25T00:00:00+10:00`, respectively, and normalize to `1972-12-25T14:00:00Z` and `1972-12-24T14:00:00Z`. ).
`op:gDay-equal(xs:gDay("---12"), xs:gDay("---12Z"))`	false()

9.5 Component extraction functions on dates and times

The date and time datatypes may be considered to be composite datatypes in that they contain distinct properties or components. The extraction functions specified below extract a single component from a date or time value. In all cases the local value (that is, the original value as written, without any timezone adjustment) is used.

Note:

A time written as 24:00:00 is treated as 00:00:00 on the following day.

Function	Meaning
`fn:year-from-dateTime`	Returns the year component of an `xs:dateTime`.
`fn:month-from-dateTime`	Returns the month component of an `xs:dateTime`.
`fn:day-from-dateTime`	Returns the day component of an `xs:dateTime`.
`fn:hours-from-dateTime`	Returns the hours component of an `xs:dateTime`.
`fn:minutes-from-dateTime`	Returns the minute component of an `xs:dateTime`.
`fn:seconds-from-dateTime`	Returns the seconds component of an `xs:dateTime`.
`fn:timezone-from-dateTime`	Returns the timezone component of an `xs:dateTime`.
`fn:year-from-date`	Returns the year component of an `xs:date`.
`fn:month-from-date`	Returns the month component of an `xs:date`.
`fn:day-from-date`	Returns the day component of an `xs:date`.
`fn:timezone-from-date`	Returns the timezone component of an `xs:date`.
`fn:hours-from-time`	Returns the hours component of an `xs:time`.
`fn:minutes-from-time`	Returns the minutes component of an `xs:time`.
`fn:seconds-from-time`	Returns the seconds component of an `xs:time`.
`fn:timezone-from-time`	Returns the timezone component of an `xs:time`.

9.5.1 fn:year-from-dateTime

Summary

Returns the year component of an xs:dateTime.

Signature

`fn:year-from-dateTime`(
`$value`	`as` `xs:dateTime?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer representing the year component in the local value of $value. The result may be negative.

Notes

Ignoring complications that arise with midnight on the last day of the year, the year returned is the same numeric value that appears in the lexical representation, which for negative years means the meaning may vary depending on whether XSD 1.0 or XSD 1.1 conventions are in use.

Examples

Expression:	year-from-dateTime( xs:dateTime("1999-05-31T13:20:00-05:00") )
Result:	1999
Expression:	year-from-dateTime( xs:dateTime("1999-05-31T21:30:00-05:00") )
Result:	1999
Expression:	year-from-dateTime( xs:dateTime("1999-12-31T19:20:00") )
Result:	1999
Expression:	year-from-dateTime( xs:dateTime("1999-12-31T24:00:00") )
Result:	2000
Expression:	year-from-dateTime( xs:dateTime("-0002-06-06T00:00:00") )
Result:	-2 (The result is the same whether XSD 1.0 or 1.1 is in use, despite the absence of a year 0 in the XSD 1.0 value space.)

9.5.2 fn:month-from-dateTime

Summary

Returns the month component of an xs:dateTime.

Signature

`fn:month-from-dateTime`(
`$value`	`as` `xs:dateTime?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer between 1 and 12, both inclusive, representing the month component in the local value of $value.

Examples

Expression:	month-from-dateTime( xs:dateTime("1999-05-31T13:20:00-05:00") )
Result:	5
Expression:	month-from-dateTime( xs:dateTime("1999-12-31T19:20:00-05:00") )
Result:	12
Expression:	month-from-dateTime( adjust-dateTime-to-timezone( xs:dateTime("1999-12-31T19:20:00-05:00"), xs:dayTimeDuration("PT0S") ) )
Result:	1

9.5.3 fn:day-from-dateTime

Summary

Returns the day component of an xs:dateTime.

Signature

`fn:day-from-dateTime`(
`$value`	`as` `xs:dateTime?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer between 1 and 31, both inclusive, representing the day component in the local value of $value.

Examples

Expression:	day-from-dateTime( xs:dateTime("1999-05-31T13:20:00-05:00") )
Result:	31
Expression:	day-from-dateTime( xs:dateTime("1999-12-31T20:00:00-05:00") )
Result:	31
Expression:	day-from-dateTime( adjust-dateTime-to-timezone( xs:dateTime("1999-12-31T19:20:00-05:00"), xs:dayTimeDuration("PT0S") ) )
Result:	1

9.5.4 fn:hours-from-dateTime

Summary

Returns the hours component of an xs:dateTime.

Signature

`fn:hours-from-dateTime`(
`$value`	`as` `xs:dateTime?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer between 0 and 23, both inclusive, representing the hours component in the local value of $value.

Examples

Expression:	hours-from-dateTime( xs:dateTime("1999-05-31T08:20:00-05:00") )
Result:	8
Expression:	hours-from-dateTime( xs:dateTime("1999-12-31T21:20:00-05:00") )
Result:	21
Expression:	hours-from-dateTime( adjust-dateTime-to-timezone( xs:dateTime("1999-12-31T21:20:00-05:00"), xs:dayTimeDuration("PT0S") ) )
Result:	2
Expression:	hours-from-dateTime( xs:dateTime("1999-12-31T12:00:00") )
Result:	12
Expression:	hours-from-dateTime( xs:dateTime("1999-12-31T24:00:00") )
Result:	0

9.5.5 fn:minutes-from-dateTime

Summary

Returns the minute component of an xs:dateTime.

Signature

`fn:minutes-from-dateTime`(
`$value`	`as` `xs:dateTime?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer value between 0 and 59, both inclusive, representing the minute component in the local value of $value.

Examples

Expression:	minutes-from-dateTime( xs:dateTime("1999-05-31T13:20:00-05:00") )
Result:	20
Expression:	minutes-from-dateTime( xs:dateTime("1999-05-31T13:30:00+05:30") )
Result:	30

9.5.6 fn:seconds-from-dateTime

Summary

Returns the seconds component of an xs:dateTime.

Signature

`fn:seconds-from-dateTime`(
`$value`	`as` `xs:dateTime?`
) `as` `xs:decimal?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:decimal value greater than or equal to zero and less than 60, representing the seconds and fractional seconds in the local value of $value.

Examples

Expression:	seconds-from-dateTime( xs:dateTime("1999-05-31T13:20:00-05:00") )
Result:	0

9.5.7 fn:timezone-from-dateTime

Summary

Returns the timezone component of an xs:dateTime.

Signature

`fn:timezone-from-dateTime`(
`$value`	`as` `xs:dateTime?`
) `as` `xs:dayTimeDuration?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns the timezone component of $value, if any. If $value has a timezone component, then the result is an xs:dayTimeDuration that indicates deviation from UTC; its value may range from +14:00 to -14:00 hours, both inclusive. If $value has no timezone component, the result is the empty sequence.

Examples

Expression:	timezone-from-dateTime( xs:dateTime("1999-05-31T13:20:00-05:00") )
Result:	xs:dayTimeDuration("-PT5H")
Expression:	timezone-from-dateTime( xs:dateTime("2000-06-12T13:20:00Z") )
Result:	xs:dayTimeDuration("PT0S")
Expression:	timezone-from-dateTime( xs:dateTime("2004-08-27T00:00:00") )
Result:	()

9.5.8 fn:year-from-date

Summary

Returns the year component of an xs:date.

Signature

`fn:year-from-date`(
`$value`	`as` `xs:date?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer representing the year in the local value of $value. The value may be negative.

Notes

The year returned is the same numeric value that appears in the lexical representation, which for negative years means the meaning may vary depending on whether XSD 1.0 or XSD 1.1 conventions are in use.

Examples

Expression	Result
year-from-date( xs:date("1999-05-31") )	1999
year-from-date( xs:date("2000-01-01+05:00") )	2000
year-from-date( xs:date("-0002-06-01") )	-2 (The result is the same whether XSD 1.0 or 1.1 is in use, despite the absence of a year 0 in the XSD 1.0 value space.)

9.5.9 fn:month-from-date

Summary

Returns the month component of an xs:date.

Signature

`fn:month-from-date`(
`$value`	`as` `xs:date?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer between 1 and 12, both inclusive, representing the month component in the local value of $value.

Examples

Expression	Result
month-from-date( xs:date("1999-05-31-05:00") )	5
month-from-date( xs:date("2000-01-01+05:00") )	1

9.5.10 fn:day-from-date

Summary

Returns the day component of an xs:date.

Signature

`fn:day-from-date`(
`$value`	`as` `xs:date?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer between 1 and 31, both inclusive, representing the day component in the localized value of $value.

Examples

Expression	Result
day-from-date( xs:date("1999-05-31-05:00") )	31
day-from-date( xs:date("2000-01-01+05:00") )	1

9.5.11 fn:timezone-from-date

Summary

Returns the timezone component of an xs:date.

Signature

`fn:timezone-from-date`(
`$value`	`as` `xs:date?`
) `as` `xs:dayTimeDuration?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Examples

Expression	Result
timezone-from-date( xs:date("1999-05-31-05:00") )	xs:dayTimeDuration("-PT5H")
timezone-from-date( xs:date("2000-06-12Z") )	xs:dayTimeDuration("PT0S")

9.5.12 fn:hours-from-time

Summary

Returns the hours component of an xs:time.

Signature

`fn:hours-from-time`(
`$value`	`as` `xs:time?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer between 0 and 23, both inclusive, representing the value of the hours component in the local value of $value.

Examples

Expression	Result
Assume that the dynamic context provides an implicit timezone value of `-05:00`.
`hours-from-time(xs:time("11:23:00"))`	11
`hours-from-time(xs:time("21:23:00"))`	21
`hours-from-time(xs:time("01:23:00+05:00"))`	1
hours-from-time( adjust-time-to-timezone( xs:time("01:23:00+05:00"), xs:dayTimeDuration("PT0S") ) )	20
`hours-from-time(xs:time("24:00:00"))`	0

9.5.13 fn:minutes-from-time

Summary

Returns the minutes component of an xs:time.

Signature

`fn:minutes-from-time`(
`$value`	`as` `xs:time?`
) `as` `xs:integer?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:integer value between 0 and 59, both inclusive, representing the value of the minutes component in the local value of $value.

Examples

Expression	Result
`minutes-from-time(xs:time("13:00:00Z"))`	0

9.5.14 fn:seconds-from-time

Summary

Returns the seconds component of an xs:time.

Signature

`fn:seconds-from-time`(
`$value`	`as` `xs:time?`
) `as` `xs:decimal?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Otherwise, the function returns an xs:decimal value greater than or equal to zero and less than 60, representing the seconds and fractional seconds in the local value of $value.

Examples

Expression	Result
`seconds-from-time(xs:time("13:20:10.5"))`	10.5

9.5.15 fn:timezone-from-time

Summary

Returns the timezone component of an xs:time.

Signature

`fn:timezone-from-time`(
`$value`	`as` `xs:time?`
) `as` `xs:dayTimeDuration?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, the function returns the empty sequence.

Examples

Expression	Result
`timezone-from-time(xs:time("13:20:00-05:00"))`	xs:dayTimeDuration("-PT5H")
`timezone-from-time(xs:time("13:20:00"))`	()

9.6 Timezone adjustment functions on dates and time values

Function	Meaning
`fn:adjust-dateTime-to-timezone`	Adjusts an `xs:dateTime` value to a specific timezone, or to no timezone at all.
`fn:adjust-date-to-timezone`	Adjusts an `xs:date` value to a specific timezone, or to no timezone at all; the result is the date in the target timezone that contains the starting instant of the supplied date.
`fn:adjust-time-to-timezone`	Adjusts an `xs:time` value to a specific timezone, or to no timezone at all.

These functions adjust the timezone component of an xs:dateTime, xs:date or xs:time value. The $timezone argument to these functions is defined as an xs:dayTimeDuration but must be a valid timezone value.

9.6.1 fn:adjust-dateTime-to-timezone

Summary

Adjusts an xs:dateTime value to a specific timezone, or to no timezone at all.

Signature

`fn:adjust-dateTime-to-timezone`(
`$value`	`as` `xs:dateTime?`,
`$timezone`	`as` `xs:dayTimeDuration?`	`:=` `fn:implicit-timezone()`
) `as` `xs:dateTime?`

Properties

The one-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

The two-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $timezone is not specified, then the effective value of $timezone is the value of the implicit timezone in the dynamic context.

If $value is the empty sequence, then the function returns the empty sequence.

If $value does not have a timezone component and $timezone is the empty sequence, then the result is $value.

If $value does not have a timezone component and $timezone is not the empty sequence, then the result is $value with $timezone as the timezone component.

If $value has a timezone component and $timezone is the empty sequence, then the result is the local value of $value without its timezone component.

If $value has a timezone component and $timezone is not the empty sequence, then the result is the xs:dateTime value that is equal to $value and that has a timezone component equal to $timezone.

Error Conditions

A dynamic error is raised [err:FODT0003] if $timezone is less than -PT14H or greater than PT14H or is not an integral number of minutes.

Examples

Variables
let $tz-10 := xs:dayTimeDuration("-PT10H")

Assume the dynamic context provides an implicit timezone of `-05:00 (-PT5H0M)`.
Expression:	adjust-dateTime-to-timezone( xs:dateTime('2002-03-07T10:00:00') )
Result:	xs:dateTime('2002-03-07T10:00:00-05:00')
Expression:	adjust-dateTime-to-timezone( xs:dateTime('2002-03-07T10:00:00-07:00') )
Result:	xs:dateTime('2002-03-07T12:00:00-05:00')
Expression:	adjust-dateTime-to-timezone( xs:dateTime('2002-03-07T10:00:00'), $tz-10 )
Result:	xs:dateTime('2002-03-07T10:00:00-10:00')
Expression:	adjust-dateTime-to-timezone( xs:dateTime('2002-03-07T10:00:00-07:00'), $tz-10 )
Result:	xs:dateTime('2002-03-07T07:00:00-10:00')
Expression:	adjust-dateTime-to-timezone( xs:dateTime('2002-03-07T10:00:00-07:00'), xs:dayTimeDuration("PT10H") )
Result:	xs:dateTime('2002-03-08T03:00:00+10:00')
Expression:	adjust-dateTime-to-timezone( xs:dateTime('2002-03-07T00:00:00+01:00'), xs:dayTimeDuration("-PT8H") )
Result:	xs:dateTime('2002-03-06T15:00:00-08:00')
Expression:	adjust-dateTime-to-timezone( xs:dateTime('2002-03-07T10:00:00'), () )
Result:	xs:dateTime('2002-03-07T10:00:00')
Expression:	adjust-dateTime-to-timezone( xs:dateTime('2002-03-07T10:00:00-07:00'), () )
Result:	xs:dateTime('2002-03-07T10:00:00')

9.6.2 fn:adjust-date-to-timezone

Summary

Adjusts an xs:date value to a specific timezone, or to no timezone at all; the result is the date in the target timezone that contains the starting instant of the supplied date.

Signature

`fn:adjust-date-to-timezone`(
`$value`	`as` `xs:date?`,
`$timezone`	`as` `xs:dayTimeDuration?`	`:=` `fn:implicit-timezone()`
) `as` `xs:date?`

Properties

The one-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

The two-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $timezone is not specified, then the effective value of $timezone is the value of the implicit timezone in the dynamic context.

If $value is the empty sequence, then the function returns the empty sequence.

If $value does not have a timezone component and $timezone is the empty sequence, then the result is $value.

If $value does not have a timezone component and $timezone is not the empty sequence, then the result is $value with $timezone as the timezone component.

If $value has a timezone component and $timezone is the empty sequence, then the result is the local value of $value without its timezone component.

If $value has a timezone component and $timezone is not the empty sequence, then:

Let $dt be the value of fn:dateTime($arg, xs:time('00:00:00')).
Let $adt be the value of fn:adjust-dateTime-to-timezone($dt, $timezone)
The function returns the value of xs:date($adt)

Error Conditions

A dynamic error is raised [err:FODT0003] if $timezone is less than -PT14H or greater than PT14H or is not an integral number of minutes.

Examples

Variables
let $tz-10 := xs:dayTimeDuration("-PT10H")

Expression	Result
Assume the dynamic context provides an implicit timezone of `-05:00 (-PT5H0M)`.
adjust-date-to-timezone( xs:date("2002-03-07") )	xs:date("2002-03-07-05:00")
adjust-date-to-timezone( xs:date("2002-03-07-07:00") )	xs:date("2002-03-07-05:00") (`$value` is converted to `xs:dateTime("2002-03-07T00:00:00-07:00")`. This is adjusted to the implicit timezone, giving `"2002-03-07T02:00:00-05:00"`. ).
adjust-date-to-timezone( xs:date("2002-03-07"), $tz-10 )	xs:date("2002-03-07-10:00")
adjust-date-to-timezone( xs:date("2002-03-07-07:00"), $tz-10 )	xs:date("2002-03-06-10:00") (`$value` is converted to `xs:dateTime("2002-03-07T00:00:00-07:00")`. This is adjusted to the given timezone, giving `"2002-03-06T21:00:00-10:00"`. ).
adjust-date-to-timezone( xs:date("2002-03-07"), () )	xs:date("2002-03-07")
adjust-date-to-timezone( xs:date("2002-03-07-07:00"), () )	xs:date("2002-03-07")

9.6.3 fn:adjust-time-to-timezone

Summary

Adjusts an xs:time value to a specific timezone, or to no timezone at all.

Signature

`fn:adjust-time-to-timezone`(
`$value`	`as` `xs:time?`,
`$timezone`	`as` `xs:dayTimeDuration?`	`:=` `fn:implicit-timezone()`
) `as` `xs:time?`

Properties

The one-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

The two-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $timezone is not specified, then the effective value of $timezone is the value of the implicit timezone in the dynamic context.

If $value is the empty sequence, then the function returns the empty sequence.

If $value does not have a timezone component and $timezone is the empty sequence, then the result is $value.

If $value does not have a timezone component and $timezone is not the empty sequence, then the result is $value with $timezone as the timezone component.

If $value has a timezone component and $timezone is the empty sequence, then the result is the localized value of $value without its timezone component.

If $value has a timezone component and $timezone is not the empty sequence, then:

Let $dt be the xs:dateTime value fn:dateTime(xs:date('1972-12-31'), $value).
Let $adt be the value of fn:adjust-dateTime-to-timezone($dt, $timezone)
The function returns the xs:time value xs:time($adt).

Error Conditions

A dynamic error is raised [err:FODT0003] if $timezone is less than -PT14H or greater than PT14H or if does not contain an integral number of minutes.

Examples

Variables
let $tz-10 := xs:dayTimeDuration("-PT10H")

Expression	Result
Assume the dynamic context provides an implicit timezone of `-05:00 (-PT5H0M)`.
adjust-time-to-timezone( xs:time("10:00:00") )	xs:time("10:00:00-05:00")
adjust-time-to-timezone( xs:time("10:00:00-07:00") )	xs:time("12:00:00-05:00")
adjust-time-to-timezone( xs:time("10:00:00"), $tz-10 )	xs:time("10:00:00-10:00")
adjust-time-to-timezone( xs:time("10:00:00-07:00"), $tz-10 )	xs:time("07:00:00-10:00")
adjust-time-to-timezone( xs:time("10:00:00"), () )	xs:time("10:00:00")
adjust-time-to-timezone( xs:time("10:00:00-07:00"), () )	xs:time("10:00:00")
adjust-time-to-timezone( xs:time("10:00:00-07:00"), xs:dayTimeDuration("PT10H") )	xs:time("03:00:00+10:00")

9.7 Arithmetic operators on durations, dates and times

These functions support adding or subtracting a duration value to or from an xs:dateTime, an xs:date or an xs:time value. Appendix E of [XML Schema Part 2: Datatypes Second Edition] describes an algorithm for performing such operations.

Function	Meaning
`op:subtract-dateTimes`	Returns an `xs:dayTimeDuration` representing the amount of elapsed time between the instants `arg2` and `arg1`.
`op:subtract-dates`	Returns the `xs:dayTimeDuration` that corresponds to the elapsed time between the starting instant of `$arg2` and the starting instant of `$arg2`.
`op:subtract-times`	Returns the `xs:dayTimeDuration` that corresponds to the elapsed time between the values of `$arg2` and `$arg1` treated as times on the same date.
`op:add-yearMonthDuration-to-dateTime`	Returns the `xs:dateTime` that is a given duration after a specified `xs:dateTime` (or before, if the duration is negative).
`op:add-dayTimeDuration-to-dateTime`	Returns the `xs:dateTime` that is a given duration after a specified `xs:dateTime` (or before, if the duration is negative).
`op:subtract-yearMonthDuration-from-dateTime`	Returns the `xs:dateTime` that is a given duration before a specified `xs:dateTime` (or after, if the duration is negative).
`op:subtract-dayTimeDuration-from-dateTime`	Returns the `xs:dateTime` that is a given duration before a specified `xs:dateTime` (or after, if the duration is negative).
`op:add-yearMonthDuration-to-date`	Returns the `xs:date` that is a given duration after a specified `xs:date` (or before, if the duration is negative).
`op:add-dayTimeDuration-to-date`	Returns the `xs:date` that is a given duration after a specified `xs:date` (or before, if the duration is negative).
`op:subtract-yearMonthDuration-from-date`	Returns the `xs:date` that is a given duration before a specified `xs:date` (or after, if the duration is negative).
`op:subtract-dayTimeDuration-from-date`	Returns the `xs:date` that is a given duration before a specified `xs:date` (or after, if the duration is negative).
`op:add-dayTimeDuration-to-time`	Returns the `xs:time` value that is a given duration after a specified `xs:time` (or before, if the duration is negative or causes wrap-around past midnight)
`op:subtract-dayTimeDuration-from-time`	Returns the `xs:time` value that is a given duration before a specified `xs:time` (or after, if the duration is negative or causes wrap-around past midnight)

9.7.1 Limits and precision

A processor that limits the number of digits in date and time datatype representations may encounter overflow and underflow conditions when it tries to execute the functions in this section. In these situations, the processor must return P0M or PT0S in case of duration underflow and 00:00:00 in case of time underflow. It must raise a dynamic error [err:FODT0001] in case of overflow.

The value spaces of the two totally ordered subtypes of xs:duration described in 8.1.1 Subtypes of duration are xs:integer months for xs:yearMonthDuration and xs:decimal seconds for xs:dayTimeDuration. If a processor limits the number of digits allowed in the representation of xs:integer and xs:decimal then overflow and underflow situations can arise when it tries to execute the functions in 8.5 Arithmetic operators on durations. In these situations the processor must return zero in case of numeric underflow and P0M or PT0S in case of duration underflow. It must raise a dynamic error [err:FODT0002] in case of overflow.

9.7.2 op:subtract-dateTimes

Summary

Returns an xs:dayTimeDuration representing the amount of elapsed time between the instants arg2 and arg1.

Operator Mapping

Defines the semantics of the - operator when applied to two xs:dateTime values.

Signature

`op:subtract-dateTimes`(
`$arg1`	`as` `xs:dateTime`,
`$arg2`	`as` `xs:dateTime`
) `as` `xs:dayTimeDuration`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

If either $arg1 or $arg2 do not contain an explicit timezone then, for the purpose of the operation, the implicit timezone provided by the dynamic context (See Section C.2 Dynamic Context Components ^XP31.) is assumed to be present as part of the value.

The function returns the elapsed time between the date/time instant arg2 and the date/time instant arg1, computed according to the algorithm given in Appendix E of [XML Schema Part 2: Datatypes Second Edition], and expressed as a xs:dayTimeDuration.

If the normalized value of $arg1 precedes in time the normalized value of $arg2, then the returned value is a negative duration.

Examples

Assume that the dynamic context provides an implicit timezone value of `-05:00`.
Expression:	op:subtract-dateTimes( xs:dateTime("2000-10-30T06:12:00"), xs:dateTime("1999-11-28T09:00:00Z") )
Result:	xs:dayTimeDuration("P337DT2H12M")

9.7.3 op:subtract-dates

Summary

Returns the xs:dayTimeDuration that corresponds to the elapsed time between the starting instant of $arg2 and the starting instant of $arg2.

Operator Mapping

Defines the semantics of the - operator when applied to two xs:date values.

Signature

`op:subtract-dates`(
`$arg1`	`as` `xs:date`,
`$arg2`	`as` `xs:date`
) `as` `xs:dayTimeDuration`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

The starting instant of an xs:date is the xs:dateTime at 00:00:00 on that date.

The function returns the result of subtracting the two starting instants using op:subtract-dateTimes.

If the starting instant of $arg1 precedes in time the starting instant of $arg2, then the returned value is a negative duration.

Examples

Expression	Result
Assume that the dynamic context provides an implicit timezone value of `Z`.
op:subtract-dates( xs:date("2000-10-30"), xs:date("1999-11-28") )	xs:dayTimeDuration("P337D") (The normalized values of the two starting instants are `{2000, 10, 30, 0, 0, 0, xs:dayTimeDuration("PT0S")}` and `{1999, 11, 28, 0, 0, 0, xs:dayTimeDuration("PT0S")}`.)
Now assume that the dynamic context provides an implicit timezone value of `+05:00`.
op:subtract-dates( xs:date("2000-10-30"), xs:date("1999-11-28Z") )	xs:dayTimeDuration("P336DT19H") ( The normalized values of the two starting instants are `{2000, 10, 29, 19, 0, 0, xs:dayTimeDuration("PT0S")}` and `{1999, 11, 28, 0, 0, 0, xs:dayTimeDuration("PT0S")}`.)
op:subtract-dates( xs:date("2000-10-15-05:00"), xs:date("2000-10-10+02:00") )	xs:dayTimeDuration("P5DT7H")

9.7.4 op:subtract-times

Summary

Returns the xs:dayTimeDuration that corresponds to the elapsed time between the values of $arg2 and $arg1 treated as times on the same date.

Operator Mapping

Defines the semantics of the - operator when applied to two xs:time values.

Signature

`op:subtract-times`(
`$arg1`	`as` `xs:time`,
`$arg2`	`as` `xs:time`
) `as` `xs:dayTimeDuration`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

The function returns the result of the expression:

op-subtract-dateTimes(
        dateTime(xs:date('1972-12-31'), $arg1),
        dateTime(xs:date('1972-12-31'), $arg2))

Notes

Any other reference date would work equally well.

Examples

Expression	Result
Assume that the dynamic context provides an implicit timezone value of `-05:00`. Assume, also, that the date components of the reference `xs:dateTime` correspond to `"1972-12-31"`.
op:subtract-times( xs:time("11:12:00Z"), xs:time("04:00:00") )	xs:dayTimeDuration("PT2H12M") (This is obtained by subtracting from the `xs:dateTime` value `{1972, 12, 31, 11, 12, 0, xs:dayTimeDuration("PT0S")}` the `xs:dateTime` value `{1972, 12, 31, 9, 0, 0, xs:dayTimeDuration("PT0S")}`.)
op:subtract-times( xs:time("11:00:00-05:00"), xs:time("21:30:00+05:30") )	xs:dayTimeDuration("PT0S") (The two `xs:dateTime` values are `{1972, 12, 31, 11, 0, 0, xs:dayTimeDuration("-PT5H")}` and `{1972, 12, 31, 21, 30, 0, xs:dayTimeDuration("PT5H30M")}`. These normalize to `{1972, 12, 31, 16, 0, 0, xs:dayTimeDuration("PT0S")}` and `{1972, 12, 31, 16, 0, 0, xs:dayTimeDuration("PT0S")}`. ).
op:subtract-times( xs:time("17:00:00-06:00"), xs:time("08:00:00+09:00") )	xs:dayTimeDuration("P1D") (The two normalized `xs:dateTime` values are `{1972, 12, 31, 23, 0, 0, xs:dayTimeDuration("PT0S")}` and `{1972, 12, 30, 23, 0, 0, xs:dayTimeDuration("PT0S")}`.)
op:subtract-times( xs:time("24:00:00"), xs:time("23:59:59") )	xs:dayTimeDuration("-PT23H59M59S") (The two normalized `xs:dateTime` values are `{1972, 12, 31, 0, 0, 0, ()}` and `{1972, 12, 31, 23, 59, 59.0, ()}`.)

9.7.5 op:add-yearMonthDuration-to-dateTime

Summary

Returns the xs:dateTime that is a given duration after a specified xs:dateTime (or before, if the duration is negative).

Operator Mapping

Defines the semantics of the + operator when applied to an xs:dateTime and an xs:yearMonthDuration value.

Signature

`op:add-yearMonthDuration-to-dateTime`(
`$arg1`	`as` `xs:dateTime`,
`$arg2`	`as` `xs:yearMonthDuration`
) `as` `xs:dateTime`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the result of adding $arg2 to the value of $arg1 using the algorithm described in Appendix E of [XML Schema Part 2: Datatypes Second Edition], disregarding the rule about leap seconds. If $arg2 is negative, then the result xs:dateTime precedes $arg1.

The result has the same timezone as $arg1. If $arg1 has no timezone, the result has no timezone.

Examples

Expression:	op:add-yearMonthDuration-to-dateTime( xs:dateTime("2000-10-30T11:12:00"), xs:yearMonthDuration("P1Y2M") )
Result:	xs:dateTime("2001-12-30T11:12:00")

9.7.6 op:add-dayTimeDuration-to-dateTime

Summary

Returns the xs:dateTime that is a given duration after a specified xs:dateTime (or before, if the duration is negative).

Operator Mapping

Defines the semantics of the + operator when applied to an xs:dateTime and an xs:dayTimeDuration value.

Signature

`op:add-dayTimeDuration-to-dateTime`(
`$arg1`	`as` `xs:dateTime`,
`$arg2`	`as` `xs:dayTimeDuration`
) `as` `xs:dateTime`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The result has the same timezone as $arg1. If $arg1 has no timezone, the result has no timezone.

Examples

Expression:	op:add-dayTimeDuration-to-dateTime( xs:dateTime("2000-10-30T11:12:00"), xs:dayTimeDuration("P3DT1H15M") )
Result:	xs:dateTime("2000-11-02T12:27:00")

9.7.7 op:subtract-yearMonthDuration-from-dateTime

Summary

Returns the xs:dateTime that is a given duration before a specified xs:dateTime (or after, if the duration is negative).

Operator Mapping

Defines the semantics of the - operator when applied to an xs:dateTime and an xs:yearMonthDuration value.

Signature

`op:subtract-yearMonthDuration-from-dateTime`(
`$arg1`	`as` `xs:dateTime`,
`$arg2`	`as` `xs:yearMonthDuration`
) `as` `xs:dateTime`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the xs:dateTime computed by negating $arg2 and adding the result to $arg1 using the function op:add-yearMonthDuration-to-dateTime.

Examples

Expression:	op:subtract-yearMonthDuration-from-dateTime( xs:dateTime("2000-10-30T11:12:00"), xs:yearMonthDuration("P1Y2M") )
Result:	xs:dateTime("1999-08-30T11:12:00")

9.7.8 op:subtract-dayTimeDuration-from-dateTime

Summary

Returns the xs:dateTime that is a given duration before a specified xs:dateTime (or after, if the duration is negative).

Operator Mapping

Defines the semantics of the - operator when applied to an xs:dateTime an and xs:dayTimeDuration values

Signature

`op:subtract-dayTimeDuration-from-dateTime`(
`$arg1`	`as` `xs:dateTime`,
`$arg2`	`as` `xs:dayTimeDuration`
) `as` `xs:dateTime`

Rules

The function returns the xs:dateTime computed by negating $arg2 and adding the result to $arg1 using the function op:add-dayTimeDuration-to-dateTime.

Examples

Expression:	op:subtract-dayTimeDuration-from-dateTime( xs:dateTime("2000-10-30T11:12:00"), xs:dayTimeDuration("P3DT1H15M") )
Result:	xs:dateTime("2000-10-27T09:57:00")

9.7.9 op:add-yearMonthDuration-to-date

Summary

Returns the xs:date that is a given duration after a specified xs:date (or before, if the duration is negative).

Operator Mapping

Defines the semantics of the + operator when applied to an xs:date and an xs:yearMonthDuration value.

Signature

`op:add-yearMonthDuration-to-date`(
`$arg1`	`as` `xs:date`,
`$arg2`	`as` `xs:yearMonthDuration`
) `as` `xs:date`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the result of casting $arg1 to an xs:dateTime, adding $arg2 using the function op:add-yearMonthDuration-to-dateTime, and casting the result back to an xs:date.

Examples

Expression:	op:add-yearMonthDuration-to-date( xs:date("2000-10-30"), xs:yearMonthDuration("P1Y2M") )
Result:	xs:date("2001-12-30")

9.7.10 op:add-dayTimeDuration-to-date

Summary

Returns the xs:date that is a given duration after a specified xs:date (or before, if the duration is negative).

Operator Mapping

Defines the semantics of the + operator when applied to an xs:date and an xs:dayTimeDuration value.

Signature

`op:add-dayTimeDuration-to-date`(
`$arg1`	`as` `xs:date`,
`$arg2`	`as` `xs:dayTimeDuration`
) `as` `xs:date`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the result of casting $arg1 to an xs:dateTime, adding $arg2 using the function op:add-dayTimeDuration-to-dateTime, and casting the result back to an xs:date.

Examples

Expression:	op:add-dayTimeDuration-to-date( xs:date("2004-10-30Z"), xs:dayTimeDuration("P2DT2H30M0S") )
Result:	xs:date("2004-11-01Z") ( The starting instant of the first argument is the `xs:dateTime` value `{2004, 10, 30, 0, 0, 0, xs:dayTimeDuration("PT0S")}`. Adding the second argument to this gives the `xs:dateTime` value `{2004, 11, 1, 2, 30, 0, xs:dayTimeDuration("PT0S")}`. The time components are then discarded. ).

9.7.11 op:subtract-yearMonthDuration-from-date

Summary

Returns the xs:date that is a given duration before a specified xs:date (or after, if the duration is negative).

Operator Mapping

Defines the semantics of the - operator when applied to an xs:date and an xs:yearMonthDuration value.

Signature

`op:subtract-yearMonthDuration-from-date`(
`$arg1`	`as` `xs:date`,
`$arg2`	`as` `xs:yearMonthDuration`
) `as` `xs:date`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Returns the xs:date computed by negating $arg2 and adding the result to $arg1 using the function op:add-yearMonthDuration-to-date.

Examples

Expression:	op:subtract-yearMonthDuration-from-date( xs:date("2000-10-30"), xs:yearMonthDuration("P1Y2M") )
Result:	xs:date("1999-08-30")
Expression:	op:subtract-yearMonthDuration-from-date( xs:date("2000-02-29Z"), xs:yearMonthDuration("P1Y") )
Result:	xs:date("1999-02-28Z")
Expression:	op:subtract-yearMonthDuration-from-date( xs:date("2000-10-31-05:00"), xs:yearMonthDuration("P1Y1M") )
Result:	xs:date("1999-09-30-05:00")

9.7.12 op:subtract-dayTimeDuration-from-date

Summary

Returns the xs:date that is a given duration before a specified xs:date (or after, if the duration is negative).

Operator Mapping

Defines the semantics of the - operator when applied to an xs:date and an xs:dayTimeDuration.

Signature

`op:subtract-dayTimeDuration-from-date`(
`$arg1`	`as` `xs:date`,
`$arg2`	`as` `xs:dayTimeDuration`
) `as` `xs:date`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Returns the xs:date computed by negating $arg2 and adding the result to $arg1 using the function op:add-dayTimeDuration-to-date.

Examples

Expression:	op:subtract-dayTimeDuration-from-date( xs:date("2000-10-30"), xs:dayTimeDuration("P3DT1H15M") )
Result:	xs:date("2000-10-26")

9.7.13 op:add-dayTimeDuration-to-time

Summary

Returns the xs:time value that is a given duration after a specified xs:time (or before, if the duration is negative or causes wrap-around past midnight)

Operator Mapping

Defines the semantics of the + operator when applied to an xs:time and an xs:dayTimeDuration value.

Signature

`op:add-dayTimeDuration-to-time`(
`$arg1`	`as` `xs:time`,
`$arg2`	`as` `xs:dayTimeDuration`
) `as` `xs:time`

Rules

First, the days component in the canonical lexical representation of $arg2 is set to zero (0) and the value of the resulting xs:dayTimeDuration is calculated. Alternatively, the value of $arg2 modulus 86,400 is used as the second argument. This value is added to the value of $arg1 converted to an xs:dateTime using a reference date such as 1972-12-31, and the time component of the result is returned. Note that the xs:time returned may occur in a following or preceding day and may be less than $arg1.

The result has the same timezone as $arg1. If $arg1 has no timezone, the result has no timezone.

Examples

Expression:	op:add-dayTimeDuration-to-time( xs:time("11:12:00"), xs:dayTimeDuration("P3DT1H15M") )
Result:	xs:time("12:27:00")
Expression:	op:add-dayTimeDuration-to-time( xs:time("23:12:00+03:00"), xs:dayTimeDuration("P1DT3H15M") )
Result:	xs:time("02:27:00+03:00") (That is, `{0, 0, 0, 2, 27, 0, xs:dayTimeDuration("PT3H")}`).

9.7.14 op:subtract-dayTimeDuration-from-time

Summary

Returns the xs:time value that is a given duration before a specified xs:time (or after, if the duration is negative or causes wrap-around past midnight)

Operator Mapping

Defines the semantics of the - operator when applied to an xs:time and an xs:dayTimeDuration value.

Signature

`op:subtract-dayTimeDuration-from-time`(
`$arg1`	`as` `xs:time`,
`$arg2`	`as` `xs:dayTimeDuration`
) `as` `xs:time`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the result of negating $arg2 and adding the result to $arg1 using the function op:add-dayTimeDuration-to-time.

Examples

Expression:	op:subtract-dayTimeDuration-from-time( xs:time("11:12:00"), xs:dayTimeDuration("P3DT1H15M") )
Result:	xs:time("09:57:00")
Expression:	op:subtract-dayTimeDuration-from-time( xs:time("08:20:00-05:00"), xs:dayTimeDuration("P23DT10H10M") )
Result:	xs:time("22:10:00-05:00")

9.8 Formatting dates and times

Function	Meaning
`fn:format-dateTime`	Returns a string containing an `xs:dateTime` value formatted for display.
`fn:format-date`	Returns a string containing an `xs:date` value formatted for display.
`fn:format-time`	Returns a string containing an `xs:time` value formatted for display.

Three functions are provided to represent dates and times as a string, using the conventions of a selected calendar, language, and country. The functions are presented in their customary fashion, except for the rules and examples, which are described en bloc at 9.8.4 The date/time formatting functions and 9.8.5 Examples of date and time formatting.

9.8.1 fn:format-dateTime

Summary

Returns a string containing an xs:dateTime value formatted for display.

Signature

`fn:format-dateTime`(
`$value`	`as` `xs:dateTime?`,
`$picture`	`as` `xs:string`,
`$language`	`as` `xs:string?`	`:=` `()`,
`$calendar`	`as` `xs:string?`	`:=` `()`,
`$place`	`as` `xs:string?`	`:=` `()`
) `as` `xs:string?`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on default calendar, and default language, and default place, and implicit timezone.

The five-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone, and namespaces.

Rules

See 9.8.4 The date/time formatting functions.

History

The 3rd, 4th, and 5th arguments are now optional; previously the function required either 2 or 5 arguments.

9.8.2 fn:format-date

Summary

Returns a string containing an xs:date value formatted for display.

Signature

`fn:format-date`(
`$value`	`as` `xs:date?`,
`$picture`	`as` `xs:string`,
`$language`	`as` `xs:string?`	`:=` `()`,
`$calendar`	`as` `xs:string?`	`:=` `()`,
`$place`	`as` `xs:string?`	`:=` `()`
) `as` `xs:string?`

Properties

The five-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone, and namespaces.

Rules

See 9.8.4 The date/time formatting functions.

History

The 3rd, 4th, and 5th arguments are now optional; previously the function required either 2 or 5 arguments.

9.8.3 fn:format-time

Summary

Returns a string containing an xs:time value formatted for display.

Signature

`fn:format-time`(
`$value`	`as` `xs:time?`,
`$picture`	`as` `xs:string`,
`$language`	`as` `xs:string?`	`:=` `()`,
`$calendar`	`as` `xs:string?`	`:=` `()`,
`$place`	`as` `xs:string?`	`:=` `()`
) `as` `xs:string?`

Properties

The five-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone, and namespaces.

Rules

See 9.8.4 The date/time formatting functions.

History

The 3rd, 4th, and 5th arguments are now optional; previously the function required either 2 or 5 arguments.

9.8.4 The date/time formatting functions

The fn:format-dateTime, fn:format-date, and fn:format-time functions format $value as a string using the picture string specified by the $picture argument, the calendar specified by the $calendar argument, the language specified by the $language argument, and the country or other place name specified by the $place argument. The result of the function is the formatted string representation of the supplied xs:dateTime, xs:date, or xs:time value.

[Definition] The three functions fn:format-dateTime, fn:format-date, and fn:format-time are referred to collectively as the date formatting functions.

If $value is the empty sequence, the function returns the empty sequence.

Calling the two-argument form of each of the three functions is equivalent to calling the five-argument form with each of the last three arguments set to an empty sequence.

For details of the $language, $calendar, and $place arguments, see 9.8.4.8 The language, calendar, and place arguments.

In general, the use of an invalid $picture, $language, $calendar, or $place argument results in a dynamic error [err:FOFD1340]. By contrast, use of an option in any of these arguments that is valid but not supported by the implementation is not an error, and in these cases the implementation is required to output the value in a fallback representation. More detailed rules are given below.

9.8.4.1 The picture string

The picture consists of a sequence of variable markers and literal substrings. A substring enclosed in square brackets is interpreted as a variable marker; substrings not enclosed in square brackets are taken as literal substrings. The literal substrings are optional and if present are rendered unchanged, including any whitespace. If an opening or closing square bracket is required within a literal substring, it must be doubled. The variable markers are replaced in the result by strings representing aspects of the date and/or time to be formatted. These are described in detail below.

A variable marker consists of a component specifier followed optionally by one or two presentation modifiers and/or optionally by a width modifier. Whitespace within a variable marker is ignored.

The variable marker may be separated into its components by applying the following rules:

The component specifier is always present and is always a single letter.
The width modifier may be recognized by the presence of a comma.
The substring between the component specifier and the comma (if present) or the end of the string (if there is no comma) contains the first and second presentation modifiers, both of which are optional. If this substring contains a single character, this is interpreted as the first presentation modifier. If it contains more than one character, the last character is examined: if it is valid as a second presentation modifier then it is treated as such, and the preceding part of the substring constitutes the first presentation modifier. Otherwise, the second presentation modifier is presumed absent and the whole substring is interpreted as the first presentation modifier.

The component specifier indicates the component of the date or time that is required, and takes the following values:

Specifier	Meaning	Default Presentation Modifier
Y	year (absolute value)	1
M	month in year	1
D	day in month	1
d	day in year	1
F	day of week	n
W	week in year	1
w	week in month	1
H	hour in day (24 hours)	1
h	hour in half-day (12 hours)	1
P	am/pm marker	n
m	minute in hour	01
s	second in minute	01
f	fractional seconds	1
Z	timezone	01:01
z	timezone (Same as Z, but modified where appropriate to include a prefix as a time offset using GMT, for example GMT+1 or GMT-05:00. For this component there is a fixed prefix of `GMT`, or a localized variation thereof for the chosen language, and the remainder of the value is formatted as for specifier `Z`.)	01:01
C	calendar: the name or abbreviation of a calendar name	n
E	era: the name of a baseline for the numbering of years, for example the reign of a monarch	n

A dynamic error is reported [err:FOFD1340] if the syntax of the picture is incorrect.

A dynamic error is reported [err:FOFD1350] if a component specifier within the picture refers to components that are not available in the given type of $value, for example if the picture supplied to the fn:format-time refers to the year, month, or day component.

It is not an error to include a timezone component when the supplied value has no timezone. In these circumstances the timezone component will be ignored.

The first presentation modifier indicates the style in which the value of a component is to be represented. Its value may be either:

any format token permitted as a primary format token in the second argument of the fn:format-integer function, indicating that the value of the component is to be output numerically using the specified number format (for example, 1, 01, i, I, w, W, or Ww) or
the format token n, N, or Nn, indicating that the value of the component is to be output by name, in lower-case, upper-case, or title-case respectively. Components that can be output by name include (but are not limited to) months, days of the week, timezones, and eras. If the processor cannot output these components by name for the chosen calendar and language then it must use an ·implementation-defined· fallback representation.

If a comma is to be used as a grouping separator within the format token, then there must be a width specifier. More specifically: if a variable marker contains one or more commas, then the last comma is treated as introducing the width modifier, and all others are treated as grouping separators. So [Y9,999,*] will output the year as 2,008.

It is not possible to use a closing square bracket as a grouping separator within the format token.

If the implementation does not support the use of the requested format token, it must use the default presentation modifier for that component.

If the first presentation modifier is present, then it may optionally be followed by a second presentation modifier as follows:

Modifier Meaning

either a or t indicates alphabetic or traditional numbering respectively, the default being ·implementation-defined·. This has the same meaning as in the second argument of fn:format-integer.

either c or o indicates cardinal or ordinal numbering respectively, for example 7 or seven for a cardinal number, or 7th, seventh, or 7º for an ordinal number. This has the same meaning as in the second argument of fn:format-integer. The actual representation of the ordinal form of a number may depend not only on the language, but also on the grammatical context (for example, in some languages it must agree in gender).

Note:

Although the formatting rules are expressed in terms of the rules for format tokens in fn:format-integer, the formats actually used may be specialized to the numbering of date components where appropriate. For example, in Italian, it is conventional to use an ordinal number (primo) for the first day of the month, and cardinal numbers (due, tre, quattro ...) for the remaining days. A processor may therefore use this convention to number days of the month, ignoring the presence or absence of the ordinal presentation modifier.

9.8.4.2 The Width Modifier

Whether or not a presentation modifier is included, a width modifier may be supplied. This indicates the number of characters to be included in the representation of the value.

The width modifier, if present, is introduced by a comma. It takes the form:

"," min-width ("-" max-width)?

where min-width is either an unsigned integer indicating the minimum number of characters to be output, or * indicating that there is no explicit minimum, and max-width is either an unsigned integer indicating the maximum number of characters to be output, or * indicating that there is no explicit maximum; if max-width is omitted then * is assumed.

A dynamic error ([err:FOFD1340]) is raised if min-width is present and less than one, or if max-width is present and less than one or less than min-width.

A format token containing more than one digit, such as 001 or 9999, sets the minimum and maximum width to the number of digits appearing in the format token; if a width modifier is also present, then the width modifier takes precedence.

9.8.4.3 Formatting Integer-Valued Date/Time Components

The rules in this section apply to the majority of integer-valued components: specifically M D d F W w H h m s.

In the rules below, the term decimal digit pattern has the meaning given in 4.6.1 fn:format-integer.

If the first presentation modifier takes the form of a decimal digit pattern:
1. If there is no width modifier, then the value is formatted according to the rules of the format-integer function.
2. If there is a width modifier, then the first presentation modifier is adjusted as follows:
  1. If the decimal digit pattern includes a grouping separator, the output is implementation-defined (but this is not an error).
    
    Note:
    
    Use of a width modifier together with grouping separators is inadvisable for this reason. It is never necessary to use a width modifier with a decimal digit pattern, since the same effect can be achieved by use of optional digit signs.
  2. Otherwise, the number of mandatory-digit-sign characters in the presentation modifier is increased if necessary. This is done first by replacing optional-digit-signs with mandatory-digit-signs, starting from the right, and then prepending mandatory-digit-signs to the presentation modifier, until the number of mandatory-digit-signs is equal to the minimum width. Any mandatory-digit-signs that are added by this process must use the same decimal digit family as existing mandatory-digit-signs in the presentation modifier if there are any, or ASCII digits otherwise.
  3. The maximum width, if specified, is ignored.
  4. The output is then as defined using the format-integer function with this adjusted decimal digit pattern.
If the first presentation modifiers is one of N, n, or Nn:
1. Let FN be the full name of the component, that is, the form of the name that would be used in the absence of any width modifier.
2. If FN is shorter than the minimum width, then it is padded by appending spaces to the end of the name.
3. If FN is longer than the maximum width, then it is abbreviated, either by choosing a conventional abbreviation that fits within the maximum width (for example, “Wednesday” might be abbreviated to “Weds”), or by removing characters from the end of FN until it fits within the maximum width.
For other presentation modifiers:
1. Any adjustment of the value to fit within the requested width range is implementation-defined.
2. The value should not be truncated if this results in output that will not be meaningful to users (for example, there is no sensible way to truncate Roman numerals).
3. If shorter than the minimum width, the value should be padded to the minimum width, either by appending spaces, or in some other way appropriate to the numbering scheme.

9.8.4.4 Formatting the Year Component

The rules for the year component (Y) are the same as those in 9.8.4.3 Formatting Integer-Valued Date/Time Components, except that the value of the year as output is the value of the year component of the supplied value modulo ten to the power N where N is determined as follows:

If the width modifier is present and defines a finite maximum width, then that maximum width.
Otherwise, if the first presentation modifier takes the form of a decimal-digit-pattern, then:
1. Let W be the number of optional-digit-signs and mandatory-digit-signs in that decimal-digit-pattern.
2. If W is 2 or more, then W.
Otherwise, N is infinity (that is, the year is output in full).

9.8.4.5 Formatting Fractional Seconds

The output for the fractional seconds component (f) is equivalent to the result of the following algorithm:

If the first presentation modifier contains no Unicode digit, then the output is implementation-defined.
Otherwise, the value of the fractional seconds is output as follows:
1. If there is no width modifier and the first presentation modifier comprises in its entirety a single mandatory-digit-sign (for example the default 1), then the presentation modifier is extended on the right with as many optional-digit-signs as are needed to accommodate the actual fractional seconds precision encountered in the value to be formatted.
2. If there is a width modifier, then the first presentation modifier is adjusted as follows:
  1. If a minimum width is specified, and if this exceeds the number of mandatory-digit-sign characters in the first presentation modifier, then the first presentation modifier is adjusted. This is done first by replacing optional-digit-signs with mandatory-digit-signs, starting from the left, and then appending mandatory-digit-signs to the presentation modifier, until the number of mandatory-digit-signs is equal to the minimum width. Any mandatory-digit-signs that are added by this process must use the same decimal digit family as existing mandatory-digit-signs in the presentation modifier.
  2. If a maximum width is specified, the first presentation modifier is extended on the right with as many optional-digit-signs as are needed to ensure that the number of mandatory-digit-signs and optional-digit-signs is at least equal to the maximum width.
3. The sequence of characters in the (adjusted) first presentation modifier is reversed (for example, 999'### becomes ###'999). If the result is not a valid decimal digit pattern, then the output is ·implementation-defined·.
4. The sequence of digits in the conventional decimal representation of the fractional seconds component is reversed, with insignificant zeroes removed, and the result is treated as an integer. For example, if the seconds value is 25.8235, the reversed fractional seconds value is 5328.
5. The reversed fractional seconds value is formatted using the reversed decimal digit pattern according to the rules of the fn:format-integer function. Given the examples above, the result is 5'328
6. The resulting string is reversed. In our example, the result is 823'5.
7. If the result contains more digits than the number of mandatory-digit-signs and optional-digit-signs in the decimal digit pattern, then excess digits are removed from the right hand end (that is, the value is truncated towards zero rather than being rounded). Any grouping separator that immediately precedes a removed digit is also removed.

Note:

The reason for presenting the algorithm in this way is that it enables maximum reuse of the rules defined for fn:format-integer. Since the fractional seconds value is not properly an integer, the rules do not work if used directly: for example, the positions of grouping separators need to be counted from the left rather than from the right. Implementations, as always, are free to use a different algorithm that yields the same result.

Note:

A format token consisting of a single digit, such as 1, does not constrain the number of digits in the output. In the case of fractional seconds in particular, [f001] requests three decimal digits, [f01] requests two digits, but [f1] will retain all digits in the supplied date/time value (the maximum number of digits is implementation-defined). If exactly one digit is required, this can be achieved using the component specifier [f1,1-1].

9.8.4.6 Formatting timezones

Special rules apply to the formatting of timezones. When the component specifiers Z or z are used, the rules in this section override any rules given elsewhere in the case of discrepancies.

If the date/time value to be formatted does not include a timezone offset, then the timezone component specifier is generally ignored (results in no output). The exception is where military timezones are used (format ZZ) in which case the string "J" is output, indicating local time.

When the component specifier is z, the output is the same as for component specifier Z, except that it is prefixed by the characters GMT or some localized equivalent. The prefix is omitted, however, in cases where the timezone is identified by name rather than by a numeric offset from UTC.
If the first presentation modifier is numeric and comprises one or two digits with no grouping-separator (for example 1 or 01), then the timezone is formatted as a displacement from UTC in hours, preceded by a plus or minus sign: for example -5 or +03. If the actual timezone offset is not an integral number of hours, then the minutes part of the offset is appended, separated by a colon: for example +10:30 or -1:15.
If the first presentation modifier is numeric with a grouping-separator (for example 1:01 or 01.01), then the timezone offset is output in hours and minutes, separated by the grouping separator, even if the number of minutes is zero: for example +5:00 or +10.30.
If the first presentation modifier is numeric and comprises three or four digits with no grouping-separator, for example 001 or 0001, then the timezone offset is shown in hours and minutes with no separator, for example -0500 or +1030.
If the first presentation modifier is numeric, in any of the above formats, and the second presentation modifier is t, then a zero timezone offset (that is, UTC) is output as Z instead of a signed numeric value. In this presentation modifier is absent or if the timezone offset is non-zero, then the displayed timezone offset is preceded by a - sign for negative offsets or a + sign for non-negative offsets.
If the first presentation modifier is Z, then the timezone is formatted as a military timezone letter, using the convention Z = +00:00, A = +01:00, B = +02:00, ..., M = +12:00, N = -01:00, O = -02:00, ... Y = -12:00. The letter J (meaning local time) is used in the case of a value that does not specify a timezone offset. Timezone offsets that have no representation in this system (for example Indian Standard Time, +05:30) are output as if the format 01:01 had been requested.
If the first presentation modifier is N, then the timezone is output (where possible) as a timezone name, for example EST or CET. The same timezone offset has different names in different places; it is therefore recommended that this option should be used only if a country code (see [ISO 3166-1]) or IANA timezone name (see [IANA Timezone Database]) is supplied in the $place argument. In the absence of this information, the implementation may apply a default, for example by using the timezone names that are conventional in North America. If no timezone name can be identified, the timezone offset is output using the fallback format 01:01.

The following examples illustrate options for timezone formatting.

Variable marker	`$place`	Timezone offsets (with time = 12:00:00)
		-10:00	-05:00	+00:00	+05:30	+13:00
[Z]	()	-10:00	-05:00	+00:00	+05:30	+13:00
[Z0]	()	-10	-5	+0	+5:30	+13
[Z0:00]	()	-10:00	-5:00	+0:00	+5:30	+13:00
[Z00:00]	()	-10:00	-05:00	+00:00	+05:30	+13:00
[Z0000]	()	-1000	-0500	+0000	+0530	+1300
[Z00:00t]	()	-10:00	-05:00	Z	+05:30	+13:00
[z]	()	GMT‑10:00	GMT‑05:00	GMT+00:00	GMT+05:30	GMT+13:00
[ZZ]	()	W	R	Z	+05:30	+13:00
[ZN]	"us"	HST	EST	GMT	IST	+13:00
[H00]:[M00] [ZN]	"America/New_York"	06:00 EST	12:00 EST	07:00 EST	01:30 EST	18:00 EST

If a width specifier is present when formatting a timezone, then the representation as defined in this section is padded to the minimum width as described in 9.8.4.2 The Width Modifier, but it is never shortened.

9.8.4.7 Formatting Other Components

This section applies to the remaining components: P (am/pm marker), C (calendar), and E (era).

The output for these components is entirely ·implementation-defined·. The default presentation modifier for these components is n, indicating that they are output as names (or conventional abbreviations), and the chosen names will in many cases depend on the chosen language: see 9.8.4.8 The language, calendar, and place arguments.

9.8.4.8 The language, calendar, and place arguments

The set of languages, calendars, and places that are supported in the ·date formatting functions· is ·implementation-defined·. When any of these arguments is omitted or is an empty sequence, an ·implementation-defined· default value is used.

If the fallback representation uses a different calendar from that requested, the output string must identify the calendar actually used, for example by prefixing the string with [Calendar: X] (where X is the calendar actually used), localized as appropriate to the requested language. If the fallback representation uses a different language from that requested, the output string must identify the language actually used, for example by prefixing the string with [Language: Y] (where Y is the language actually used) localized in an implementation-dependent way. If a particular component of the value cannot be output in the requested format, it should be output in the default format for that component.

The $language argument specifies the language to be used for the result string of the function. The value of the argument should be either the empty sequence or a value that would be valid for the xml:lang attribute (see [Extensible Markup Language (XML) 1.0 (Fifth Edition)]). Note that this permits the identification of sublanguages based on country codes (from [ISO 3166-1]) as well as identification of dialects and of regions within a country.

If the $language argument is omitted or is set to an empty sequence, or if it is set to an invalid value or a value that the implementation does not recognize, then the processor uses the default language defined in the dynamic context.

The language is used to select the appropriate language-dependent forms of:

names (for example, of months)
numbers expressed as words or as ordinals (twenty, 20th, twentieth)
hour convention (0-23 vs 1-24, 0-11 vs 1-12)
first day of week, first week of year

Where appropriate this choice may also take into account the value of the $place argument, though this should not be used to override the language or any sublanguage that is specified as part of the language argument.

The choice of the names and abbreviations used in any given language is ·implementation-defined·. For example, one implementation might abbreviate July as Jul while another uses Jly. In German, one implementation might represent Saturday as Samstag while another uses Sonnabend. Implementations may provide mechanisms allowing users to control such choices.

Where ordinal numbers are used, the selection of the correct representation of the ordinal (for example, the grammatical gender) may depend on the component being formatted and on its textual context in the picture string.

The calendar attribute specifies that the dateTime, date, or time supplied in the $value argument must be converted to a value in the specified calendar and then converted to a string using the conventions of that calendar.

The calendar value if present must be a valid EQName (dynamic error: [err:FOFD1340]). If it is a lexical QName then it is expanded into an expanded QName using the statically known namespaces; if it has no prefix then it represents an expanded-QName in no namespace. If the expanded QName is in no namespace, then it must identify a calendar with a designator specified below (dynamic error: [err:FOFD1340]). If the expanded QName is in a namespace then it identifies the calendar in an ·implementation-defined· way.

If the $calendar argument is omitted or is set to an empty sequence then the default calendar defined in the dynamic context is used.

Note:

The calendars listed below were known to be in use during the last hundred years. Many other calendars have been used in the past.

This specification does not define any of these calendars, nor the way that they map to the value space of the xs:date datatype in [XML Schema Part 2: Datatypes Second Edition]. There may be ambiguities when dates are recorded using different calendars. For example, the start of a new day is not simultaneous in different calendars, and may also vary geographically (for example, based on the time of sunrise or sunset). Translation of dates is therefore more reliable when the time of day is also known, and when the geographic location is known. When translating dates between one calendar and another, the processor may take account of the values of the $place and/or $language arguments, with the $place argument taking precedence.

Information about some of these calendars, and algorithms for converting between them, may be found in [Calendrical Calculations].

Designator	Calendar
AD	Anno Domini (Christian Era)
AH	Anno Hegirae (Islamic Era)
AME	Mauludi Era (solar years since Muhammad’s birth)
AM	Anno Mundi (Jewish Calendar)
AP	Anno Persici
AS	Aji Saka Era (Java)
BE	Buddhist Era
CB	Cooch Behar Era
CE	Common Era
CL	Chinese Lunar Era
CS	Chula Sakarat Era
EE	Ethiopian Era
FE	Fasli Era
ISO	ISO 8601 calendar
JE	Japanese Calendar
KE	Khalsa Era (Sikh calendar)
KY	Kali Yuga
ME	Malabar Era
MS	Monarchic Solar Era
NS	Nepal Samwat Era
OS	Old Style (Julian Calendar)
RS	Rattanakosin (Bangkok) Era
SE	Saka Era
SH	Solar Hijri (Islamic Era, used in Iran and Afghanistan)
SS	Saka Samvat
TE	Tripurabda Era
VE	Vikrama Era
VS	Vikrama Samvat Era

At least one of the above calendars must be supported. It is ·implementation-defined· which calendars are supported.

The ISO 8601 calendar ([ISO 8601]), which is included in the above list and designated ISO, is very similar to the Gregorian calendar designated AD, but it differs in several ways. The ISO calendar is intended to ensure that date and time formats can be read easily by other software, as well as being legible for human users. The ISO calendar prescribes the use of particular numbering conventions as defined in ISO 8601, rather than allowing these to be localized on a per-language basis. In particular it provides a numeric “week date” format which identifies dates by year, week of the year, and day in the week; in the ISO calendar the days of the week are numbered from 1 (Monday) to 7 (Sunday), and week 1 in any calendar year is the week (from Monday to Sunday) that includes the first Thursday of that year. The numeric values of the components year, month, day, hour, minute, and second are the same in the ISO calendar as the values used in the lexical representation of the date and time as defined in [XML Schema Part 2: Datatypes Second Edition]. The era (E component) with this calendar is either a minus sign (for negative years) or a zero-length string (for positive years). For dates before 1 January, AD 1, year numbers in the ISO and AD calendars are off by one from each other: ISO year 0000 is 1 BC, -0001 is 2 BC, etc.

ISO 8601 does not define a numbering for weeks within a month. When the w component is used, the convention to be adopted is that each Monday-to-Sunday week is considered to fall within a particular month if its Thursday occurs in that month; the weeks that fall in a particular month under this definition are numbered starting from 1. Thus, for example, 29 January 2013 falls in week 5 because the Thursday of the week (31 January 2013) is the fifth Thursday in January, and 1 February 2013 is also in week 5 for the same reason.

Note:

The value space of the date and time datatypes, as defined in XML Schema, is based on absolute points in time. The lexical space of these datatypes defines a representation of these absolute points in time using the proleptic Gregorian calendar, that is, the modern Western calendar extrapolated into the past and the future; but the value space is calendar-neutral. The ·date formatting functions· produce a representation of this absolute point in time, but denoted in a possibly different calendar. So, for example, the date whose lexical representation in XML Schema is 1502-01-11 (the day on which Pope Gregory XIII was born) might be formatted using the Old Style (Julian) calendar as 1 January 1502. This reflects the fact that there was at that time a ten-day difference between the two calendars. It would be incorrect, and would produce incorrect results, to represent this date in an element or attribute of type xs:date as 1502-01-01, even though this might reflect the way the date was recorded in contemporary documents.

When referring to years occurring in antiquity, modern historians generally use a numbering system in which there is no year zero (the year before 1 CE is thus 1 BCE). This is the convention that should be used when the requested calendar is OS (Julian) or AD (Gregorian). When the requested calendar is ISO, however, the conventions of ISO 8601 should be followed: here the year before +0001 is numbered zero. In [XML Schema Part 2: Datatypes Second Edition] (version 1.0), the value space for xs:date and xs:dateTime does not include a year zero: however, XSD 1.1 endorses the ISO 8601 convention. This means that the date on which Julius Caesar was assassinated has the ISO 8601 lexical representation -0043-03-13, but will be formatted as 15 March 44 BCE in the Julian calendar or 13 March 44 BCE in the Gregorian calendar (dependent on the chosen localization of the names of months and eras).

The intended use of the $place argument is to identify the place where an event represented by the dateTime, date, or time supplied in the $value argument took place or will take place. If the $place argument is omitted or is set to an empty sequence, then the default place defined in the dynamic context is used. If the value is supplied, and is not the empty sequence, then it should either be a country code or an IANA timezone name. If the value does not take this form, or if its value is not recognized by the implementation, then the default place defined in the dynamic context is used.

Country codes are defined in [ISO 3166-1]. Examples are "de" for Germany and "jp" for Japan. Implementations may also allow the use of codes representing subdivisions of a country from ISO 3166-2, or codes representing formerly used names of countries from ISO 3166-3
IANA timezone names are defined in the IANA timezone database [IANA Timezone Database]. Examples are "America/New_York" and "Europe/Rome".

This argument is not intended to identify the location of the user for whom the date or time is being formatted; that should be done by means of the $language attribute. This information may be used to provide additional information when converting dates between calendars or when deciding how individual components of the date and time are to be formatted. For example, different countries using the Old Style (Julian) calendar started the new year on different days, and some countries used variants of the calendar that were out of synchronization as a result of differences in calculating leap years.

The geographical area identified by a country code is defined by the boundaries as they existed at the time of the date to be formatted, or the present-day boundaries for dates in the future.

If the $place argument is supplied in the form of an IANA timezone name that is recognized by the implementation, then the date or time being formatted is adjusted to the timezone offset applicable in that timezone. For example, if the xs:dateTime value 2010-02-15T12:00:00Z is formatted with the $place argument set to America/New_York, then the output will be as if the value 2010-02-15T07:00:00-05:00 had been supplied. This adjustment takes daylight savings time into account where possible; if the date in question falls during daylight savings time in New York, then it is adjusted to timezone offset -PT4H rather than -PT5H. Adjustment using daylight savings time is only possible where the value includes a date, and where the date is within the range covered by the timezone database.

9.8.5 Examples of date and time formatting

The following examples show a selection of dates and times and the way they might be formatted. These examples assume the use of the Gregorian calendar as the default calendar.

Required Output	Expression
`2002-12-31`	`format-date($d, "[Y0001]-[M01]-[D01]")`
`12-31-2002`	`format-date($d, "[M]-[D]-[Y]")`
`31-12-2002`	`format-date($d, "[D]-[M]-[Y]")`
`31 XII 2002`	`format-date($d, "[D1] [MI] [Y]")`
`31st December, 2002`	`format-date($d, "[D1o] [MNn], [Y]", "en", (), ())`
`31 DEC 2002`	`format-date($d, "[D01] [MN,*-3] [Y0001]", "en", (), ())`
`December 31, 2002`	`format-date($d, "[MNn] [D], [Y]", "en", (), ())`
`31 Dezember, 2002`	`format-date($d, "[D] [MNn], [Y]", "de", (), ())`
`Tisdag 31 December 2002`	`format-date($d, "[FNn] [D] [MNn] [Y]", "sv", (), ())`
`[2002-12-31]`	`format-date($d, "[[[Y0001]-[M01]-[D01]]]")`
`Two Thousand and Three`	`format-date($d, "[YWw]", "en", (), ())`
`einunddreißigste Dezember`	`format-date($d, "[Dwo] [MNn]", "de", (), ())`
`3:58 PM`	`format-time($t, "[h]:[m01] [PN]", "en", (), ())`
`3:58:45 pm`	`format-time($t, "[h]:[m01]:[s01] [Pn]", "en", (), ())`
`3:58:45 PM PDT`	`format-time($t, "[h]:[m01]:[s01] [PN] [ZN,*-3]", "en", (), ())`
`3:58:45 o'clock PM PDT`	`format-time($t, "[h]:[m01]:[s01] o'clock [PN] [ZN,*-3]", "en", (), ())`
`15:58`	`format-time($t,"[H01]:[m01]")`
`15:58:45.762`	`format-time($t,"[H01]:[m01]:[s01].[f001]")`
`15:58:45 GMT+02:00`	`format-time($t,"[H01]:[m01]:[s01] [z,6-6]", "en", (), ())`
`15.58 Uhr GMT+2`	`format-time($t,"[H01]:[m01] Uhr [z]", "de", (), ())`
`3.58pm on Tuesday, 31st December`	`format-dateTime($dt, "[h].[m01][Pn] on [FNn], [D1o] [MNn]")`
`12/31/2002 at 15:58:45`	`format-dateTime($dt, "[M01]/[D01]/[Y0001] at [H01]:[m01]:[s01]")`

The following examples use calendars other than the Gregorian calendar.

Description	Request	Result
Islamic	`format-date($d, "[D١] [Mn] [Y١]", "ar", "AH", ())`	٢٦ ﺸﻭّﺍﻝ ١٤٢٣
Jewish (with Western numbering)	`format-date($d, "[D] [Mn] [Y]", "he", "AM", ())`	‏26 טבת 5763
Jewish (with traditional numbering)	`format-date($d, "[Dאt] [Mn] [Yאt]", "he", "AM", ())`	כ״ו טבת תשס״ג
Julian (Old Style)	`format-date($d, "[D] [MNn] [Y]", "en", "OS", ())`	18 December 2002
Thai	`format-date($d, "[D๑] [Mn] [Y๑]", "th", "BE", ())`	๓๑ ธันวาคม ๒๕๔๕

9.9 Parsing dates and times

Function	Meaning
`fn:parse-ietf-date`	Parses a string containing the date and time in IETF format, returning the corresponding `xs:dateTime` value.

A function is provided to parse dates and times expressed using syntax that is commonly encountered in internet protocols.

9.9.1 fn:parse-ietf-date

Summary

Parses a string containing the date and time in IETF format, returning the corresponding xs:dateTime value.

Signature

`fn:parse-ietf-date`(
`$value`	`as` `xs:string?`
) `as` `xs:dateTime?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function accepts a string matching the production input in the following grammar:

`input`	`::=`	`S? (dayname ","? S)? ((datespec S time) \| asctime) S?`
`dayname`	`::=`	`"Mon" \| "Tue" \| "Wed" \| "Thu" \| "Fri" \| "Sat" \| "Sun" \| "Monday \| "Tuesday" \| "Wednesday" \| "Thursday" \| "Friday" \| "Saturday" \| "Sunday"`
`datespec`	`::=`	`daynum dsep monthname dsep year`
`asctime`	`::=`	`monthname dsep daynum S time S year`
`dsep`	`::=`	`S \| (S? "-" S?)`
`daynum`	`::=`	`digit digit?`
`year`	`::=`	`digit digit (digit digit)?`
`digit`	`::=`	`[0-9]`
`monthname`	`::=`	`"Jan" \| "Feb" \| "Mar" \| "Apr" \| "May" \| "Jun" \| "Jul" \| "Aug" \| "Sep" \| "Oct" \| "Nov" \| "Dec"`
`time`	`::=`	`hours ":" minutes (":" seconds)? (S? timezone)?`
`hours`	`::=`	`digit digit?`
`minutes`	`::=`	`digit digit`
`seconds`	`::=`	`digit digit ("." digit+)?`
`timezone`	`::=`	`tzname \| tzoffset (S? "(" S? tzname S? ")")?`
`tzname`	`::=`	`"UT" \| "UTC" \| "GMT" \| "EST" \| "EDT" \| "CST" \| "CDT" \| "MST" \| "MDT" \| "PST" \| "PDT"`
`tzoffset`	`::=`	`("+"\|"-") hours ":"? minutes?`
`S`	`::=`	`(x09 \| x0A \| x0D \| x20)+`

The input is case-insensitive: upper-case and lower-case distinctions in the above grammar show the conventional usage, but otherwise have no significance.

If the input is an empty sequence, the result is an empty sequence.

The dayname, if present, is ignored.

The daynum, monthname, and year supply the day, month, and year of the resulting xs:dateTime value. A two-digit year must have 1900 added to it. A year such as 0070 is to be treated as given; negative years are not permitted.

The hours, minutes, and seconds (including fractional seconds) values supply the corresponding components of the resulting xs:dateTime value; if the seconds value or the fractional seconds value is absent then zero is assumed.

If both a tzoffset and a tzname are supplied then the tzname is ignored.

If a tzoffset is supplied then this defines the hours and minutes parts of the timezone offset:

If it contains a colon, this separates the hours part from the minutes part.
Otherwise, the grammar allows a sequence of from one to four digits. These are interpreted as H, HH, HMM, or HHMM respectively, where H or HH is the hours part, and MM (if present) is the minutes part.
If the minutes part is absent it defaults to 00.

If a tzname is supplied with no tzoffset then it is translated to a timezone offset as follows:

tzname	Offset
UT, UTC, GMT	00:00
EST	-05:00
EDT	-04:00
CST	-06:00
CDT	-05:00
MST	-07:00
MDT	-06:00
PST	-08:00
PDT	-07:00

If neither a tzoffset nor tzname is supplied, a timezone offset of 00:00 is assumed.

Error Conditions

A dynamic error is raised [err:FORG0010] if the input does not match the grammar, or if the resulting date/time value is invalid (for example, "31 February").

Notes

The parse-ietf-date function attempts to interpret its input as a date in any of the three formats specified by HTTP [RFC 2616].

These formats are used widely on the Internet to represent timestamps, and were specified in:

[RFC 822] (electronic mail), extended in [RFC 1123] to allow four-digit years;
[RFC 850] (Usenet Messages), obsoleted by [RFC 1036];
POSIX asctime() format

[RFC 2616] (HTTP) officially uses a subset of those three formats restricted to GMT.

The grammar for this function is slightly more liberal than the RFCs (reflecting the internet tradition of being liberal in what is accepted). For example the function:

Accepts a single-digit value where appropriate in place of a two-digit value with a leading zero (so "Wed 1 Jun" is acceptable in place of "Wed 01 Jun", and the timezone offset "-5:00" is equivalent to "-05:00")
Accepts one or more whitespace characters (x20, x09, x0A, x0D) wherever a single space is required, and allows whitespace to be omitted where it is not required for parsing
Accepts and ignores whitespace characters (x20, x09, x0A, x0D) at the start or end of the string.

In new protocols IETF recommends the format of [RFC 3339], which is based on a profile of ISO 8601 similar to that already used in XPath and XSD, but the “approximate” [RFC 822] format described here is very widely used.

An [RFC 1123] date can be generated approximately using fn:format-dateTime with a picture string of "[FNn3], [D01] [MNn3] [Y04] [H01]:[m01]:[s01] [Z0000]".

Examples

Expression	Result
`parse-ietf-date("Wed, 06 Jun 1994 07:29:35 GMT")`	xs:dateTime("1994-06-06T07:29:35Z")
`parse-ietf-date("Wed, 6 Jun 94 07:29:35 GMT")`	xs:dateTime("1994-06-06T07:29:35Z")
`parse-ietf-date("Wed Jun 06 11:54:45 EST 2013")`	xs:dateTime("2013-06-06T11:54:45-05:00")
`parse-ietf-date("Sunday, 06-Nov-94 08:49:37 GMT")`	xs:dateTime("1994-11-06T08:49:37Z")
`parse-ietf-date("Wed, 6 Jun 94 07:29:35 +0500")`	xs:dateTime("1994-06-06T07:29:35+05:00")

10 Functions related to QNames

10.1 Functions to create a QName

In addition to the xs:QName constructor function, QName values can be constructed by combining a namespace URI, prefix, and local name, or by resolving a lexical QName against the in-scope namespaces of an element node. This section defines functions that perform these operations. Leading and trailing whitespace, if present, is stripped from string arguments before the result is constructed.

Function	Meaning
`fn:QName`	Returns an `xs:QName` value formed using a supplied namespace URI and lexical QName.
`fn:parse-QName`	Returns an `xs:QName` value formed by parsing an EQName.
`fn:resolve-QName`	Returns an `xs:QName` value (that is, an expanded-QName) by taking an `xs:string` that has the lexical form of an `xs:QName` (a string in the form `"prefix:local-name"` or `"local-name"`) and resolving it using the in-scope namespaces for a given element.

10.1.1 fn:QName

Summary

Returns an xs:QName value formed using a supplied namespace URI and lexical QName.

Signature

`fn:QName`(
`$uri`	`as` `xs:string?`,
`$qname`	`as` `xs:string`
) `as` `xs:QName`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The namespace URI in the returned QName is taken from $uri. If $uri is the zero-length string or the empty sequence, it represents “no namespace”.

The prefix (or absence of a prefix) in $qname is retained in the returned xs:QName value.

The local name in the result is taken from the local part of $qname.

Error Conditions

A dynamic error is raised [err:FOCA0002] if $qname does not have the correct lexical form for an instance of xs:QName.

A dynamic error is raised [err:FOCA0002] if $uri is the zero-length string or the empty sequence, and the value of $qname contains a colon (:).

A dynamic error may be raised [err:FOCA0002] if $uri is not a valid URI (XML Namespaces 1.0) or IRI (XML Namespaces 1.1).

Examples

`fn:QName("http://www.example.com/example", "person")` returns an `xs:QName` with namespace URI `"http://www.example.com/example"`, local name `"person"` and prefix `""`.
`fn:QName("http://www.example.com/example", "ht:person")` returns an `xs:QName` with namespace URI `"http://www.example.com/example"`, local name `"person"` and prefix `"ht"`.

10.1.2 fn:parse-QName

Summary

Returns an xs:QName value formed by parsing an EQName.

Signature

`fn:parse-QName`(
`$value`	`as` `xs:string`
) `as` `xs:QName`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on namespaces.

Rules

Leading and trailing whitespace in $value is stripped.

If the resulting $value is castable to xs:NCName, the result is fn:QName("", $value): that is, a QName in no namespace.

Otherwise, if the resulting $value is in the lexical space of xs:QName (that is, if it is in the form prefix:local), the result is xs:QName($value). Note that this result depends on the in-scope prefixes in the static context, and may result in various error conditions.

Otherwise, if the resulting $value takes the form of an XPath BracedURILiteral^XP40 (that is, Q{uri}local, where the uri part may be zero-length), then the result is fn:QName(uri, local).

The rules used for parsing a BracedURILiteral^XP40 within a URIQualifiedName^XP40 are the XPath rules, not the XQuery rules (the XQuery rules require special characters such as < and & to be escaped).

Error Conditions

A dynamic error is raised [err:FOCA0002] if the supplied value of $value, after whitespace normalization, does not match the XPath production EQName^XP40

A dynamic error is raised [err:FONS0004] if the supplied value of $value, after whitespace normalization, is in the form prefix:local (with a non-absent prefix), and the prefix cannot be resolved to a namespace URI using the in-scope namespace bindings from the static context.

Examples

`fn:parse-QName("Q{http://www.example.com/example}person")` returns an `xs:QName` with namespace URI `"http://www.example.com/example"`, local name `"person"` and prefix `""`.
`fn:parse-QName("person")` returns an `xs:QName` with absent namespace URI, local name `"person"` and prefix `""`.
`fn:parse-QName("Q{}person")` returns an `xs:QName` with absent namespace URI, local name `"person"` and prefix `""`.
`fn:parse-QName("p:person")` returns an `xs:QName` with namespace URI obtained from the static context, local name `"person"` and prefix `"p"` (The result is the same as `xs:QName("p:person")`).

History

New function, accepted 2022-11-18

10.1.3 fn:resolve-QName

Summary

Returns an xs:QName value (that is, an expanded-QName) by taking an xs:string that has the lexical form of an xs:QName (a string in the form "prefix:local-name" or "local-name") and resolving it using the in-scope namespaces for a given element.

Signature

`fn:resolve-QName`(
`$value`	`as` `xs:string?`,
`$element`	`as` `element()`
) `as` `xs:QName?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, returns the empty sequence.

More specifically, the function searches the namespace bindings of $element for a binding whose name matches the prefix of $value, or the zero-length string if it has no prefix, and returns an expanded-QName whose local name is taken from the supplied $value, and whose namespace URI is taken from the string value of the namespace binding.

If the $value has no prefix, and there is no namespace binding for $element corresponding to the default (unnamed) namespace, then the resulting expanded-QName has no namespace part.

The prefix (or absence of a prefix) in the supplied $value argument is retained in the returned expanded-QName, as described in Section 2.1 Terminology^DM40.

Error Conditions

A dynamic error is raised [err:FOCA0002] if $value does not have the correct lexical form for an instance of xs:QName.

A dynamic error is raised [err:FONS0004] if $value has a prefix and there is no namespace binding for $element that matches this prefix.

Notes

Sometimes the requirement is to construct an xs:QName without using the default namespace. This can be achieved by writing:

 if (contains($value, ":")) then resolve-QName($value, $element) else
            QName("", $value)

If the requirement is to construct an xs:QName using the namespaces in the static context, then the xs:QName constructor should be used.

Examples

Assume that the element bound to `$element` has a single namespace binding bound to the prefix `eg`.
`fn:resolve-QName("hello", $element)` returns a QName with local name `"hello"` that is in no namespace.
`fn:resolve-QName("eg:myFunc", $element)` returns an `xs:QName` whose namespace URI is specified by the namespace binding corresponding to the prefix `"eg"` and whose local name is `"myFunc"`.

10.2 Functions and operators on QNames

This section specifies functions and an operator on QNames as defined in [XML Schema Part 2: Datatypes Second Edition].

Function	Meaning
`op:QName-equal`	Returns `true` if two supplied QNames have the same namespace URI and the same local part.
`fn:prefix-from-QName`	Returns the prefix component of the supplied QName.
`fn:local-name-from-QName`	Returns the local part of the supplied QName.
`fn:namespace-uri-from-QName`	Returns the namespace URI part of the supplied QName.
`fn:expanded-QName`	Returns a string representation of an `xs:QName` in the format `Q{uri}local`.
`fn:in-scope-namespaces`	Returns the in-scope namespaces of an element node, as a map.
`fn:in-scope-prefixes`	Returns the prefixes of the in-scope namespaces for an element node.
`fn:namespace-uri-for-prefix`	Returns the namespace URI of one of the in-scope namespaces for `$element`, identified by its namespace prefix.

10.2.1 op:QName-equal

Summary

Returns true if two supplied QNames have the same namespace URI and the same local part.

Operator Mapping

Defines the semantics of the eq and ne operators when applied to two values of type xs:QName.

Signature

`op:QName-equal`(
`$arg1`	`as` `xs:QName`,
`$arg2`	`as` `xs:QName`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns true if the namespace URIs of $arg1 and $arg2 are equal and the local names of $arg1 and $arg2 are equal.

Otherwise, the function returns false.

The namespace URI parts are considered equal if they are both absent^DM40, or if they are both present and equal under the rules of the fn:codepoint-equal function.

The local parts are also compared under the rules of the fn:codepoint-equal function.

Notes

The prefix parts of $arg1 and $arg2, if any, are ignored.

10.2.2 fn:prefix-from-QName

Summary

Returns the prefix component of the supplied QName.

Signature

`fn:prefix-from-QName`(
`$value`	`as` `xs:QName?`
) `as` `xs:NCName?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence the function returns the empty sequence.

If $value has no prefix component the function returns the empty sequence.

Otherwise, the function returns an xs:NCName representing the prefix component of $value.

10.2.3 fn:local-name-from-QName

Summary

Returns the local part of the supplied QName.

Signature

`fn:local-name-from-QName`(
`$value`	`as` `xs:QName?`
) `as` `xs:NCName?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence the function returns the empty sequence.

Otherwise, the function returns an xs:NCName representing the local part of $value.

Examples

Expression:	local-name-from-QName( QName("http://www.example.com/example", "person") )
Result:	"person"

10.2.4 fn:namespace-uri-from-QName

Summary

Returns the namespace URI part of the supplied QName.

Signature

`fn:namespace-uri-from-QName`(
`$value`	`as` `xs:QName?`
) `as` `xs:anyURI?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence the function returns the empty sequence.

Otherwise, the function returns an xs:anyURI representing the namespace URI part of $value.

If $value is in no namespace, the function returns the zero-length xs:anyURI.

Examples

Expression:	namespace-uri-from-QName( QName("http://www.example.com/example", "person") )
Result:	xs:anyURI("http://www.example.com/example")

10.2.5 fn:expanded-QName

Summary

Returns a string representation of an xs:QName in the format Q{uri}local.

Signature

`fn:expanded-QName`(
`$value`	`as` `xs:QName?`
) `as` `xs:string?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $value is the empty sequence, returns the empty sequence.

The result is a string in the format Q{uri}local, where:

uri is the result of fn:string(fn:namespace-uri-from-QName($value)) (which will be a zero-length string if the QName is in no namespace), and
local is the result of fn:local-name-from-QName($value).

There is no escaping of special characters in the namespace URI. If the namespace URI contains curly braces, the resulting string will not be a valid BracedURILiteral^XP40.

Examples

Expression:	QName("http://example.com/", "person") => expanded-QName()
Result:	"Q{http://example.com/}person"
Expression:	QName("", "person") => expanded-QName()
Result:	"Q{}person"

History

New function, accepted 2022-11-15.

10.2.6 fn:in-scope-namespaces

Summary

Returns the in-scope namespaces of an element node, as a map.

Signature

`fn:in-scope-namespaces`(
`$element`	`as` `element()`
) `as` `map(union(xs:NCName, enum('')), xs:anyURI)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns a map representing the prefixes of the in-scope namespaces for $element. The map contains one entry for each in-scope namespace: the key of the entry is the namespace prefix or a zero-length string, and the corresponding value is the namespace URI.

For namespace bindings that have a prefix, the key represents the prefix as an instance of xs:NCName. For the default namespace, which has no prefix, the key is the zero-length string as an instance of xs:string.

Notes

The XML namespace is in scope for every element, so the result will always include an entry with key "xml" and corresponding value http://www.w3.org/XML/1998/namespace.

Examples

Variables
let $e := <z:a xmlns="http://example.org/one" xmlns:z="http://example.org/two"> <b xmlns=""/> </z:a>

Expression	Result
`in-scope-namespaces($e)`	map{"": "http://example.org/one", "z": "http://example.org/two", "xml": "http://www.w3.org/XML/1998/namespace"}

History

New in 4.0. Accepted 2022-09-20. Note that the function signature uses notation that is not yet accepted.

10.2.7 fn:in-scope-prefixes

Summary

Returns the prefixes of the in-scope namespaces for an element node.

Signature

`fn:in-scope-prefixes`(
`$element`	`as` `element()`
) `as` `xs:string*`

Properties

This function is ·nondeterministic-wrt-ordering·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the result of the expression map:keys(fn:in-scope-namespaces($element)) (but in no defined order).

Notes

The XML namespace is in scope for every element, so the result will always include the string "xml".

History

Reformulated in 4.0, so it is now defined in terms of the new fn:in-scope-namespaces function; the semantics are unchanged.

10.2.8 fn:namespace-uri-for-prefix

Summary

Returns the namespace URI of one of the in-scope namespaces for $element, identified by its namespace prefix.

Signature

`fn:namespace-uri-for-prefix`(
`$value`	`as` `union(xs:NCName, enum(''))?`,
`$element`	`as` `element()`
) `as` `xs:anyURI?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the result of the expression map:get(fn:in-scope-namespaces($element), string($value)).

Examples

Variables
let $e := <z:a xmlns="http://example.org/one" xmlns:z="http://example.org/two"> <b xmlns=""/> </z:a>

Expression	Result
`namespace-uri-for-prefix("z", $e)`	"http://example.org/two"
`namespace-uri-for-prefix("", $e)`	"http://example.org/one"
`namespace-uri-for-prefix((), $e)`	"http://example.org/one"
`namespace-uri-for-prefix("xml", $e)`	"http://www.w3.org/XML/1998/namespace"

History

Reformulated in 4.0, so it is now defined in terms of the new fn:in-scope-namespaces function; the semantics are unchanged.

11 Operators on base64Binary and hexBinary

11.1 Comparisons of base64Binary and hexBinary values

The following comparison operators on xs:hexBinary and xs:base64Binary values are defined. Each returns a boolean value.

These functions can be used to compare any xs:hexBinary or xs:base64Binary value with any other xs:hexBinary or xs:base64Binary value: both types have the same value space, namely a sequence of octets which are treated as integers in the range 0 to 255.

Function	Meaning
`op:binary-equal`	Returns `true` if both binary values contain the same octet sequence.
`op:binary-less-than`	Returns `true` if the first argument is less than the second.

11.1.1 op:binary-equal

Summary

Returns true if both binary values contain the same octet sequence.

Operator Mapping

Defines the semantics of the eq and ne operators when applied to two xs:hexBinary or xs:base64Binary values.

Signature

`op:binary-equal`(
`$value1`	`as` `union(xs:hexBinary, xs:base64Binary)`,
`$value2`	`as` `union(xs:hexBinary, xs:base64Binary)`
) `as` `xs:boolean`

Rules

The function returns true if $value1 and $value2 are of the same length, measured in binary octets, and contain the same octets in the same order. Otherwise, it returns false.

11.1.2 op:binary-less-than

Summary

Returns true if the first argument is less than the second.

Operator Mapping

Defines the semantics of the lt operator when applied to two xs:hexBinary or xs:base64Binaryvalues. Also used in the definition of the ge operator.

Signature

`op:binary-less-than`(
`$arg1`	`as` `union(xs:hexBinary, xs:base64Binary)`,
`$arg2`	`as` `union(xs:hexBinary, xs:base64Binary)`
) `as` `xs:boolean`

Rules

Each of the two arguments are converted to a sequence of octets, $A and $B, and the first octet in each sequence, $a and $b, are compared.

If $a is empty and $b is non-empty return true.
If $b is empty return false.
Otherwise (neither $a nor $b are empty):
1. If $a and $b are identical the result is obtained by applying these same rules recursively to fn:tail($A) and fn:tail($B).
2. Otherwise, if $a is less than $b, treating the value of each octet as an unsigned integer in the range 0 to 255, then return true, otherwise return false.

12 Operators on NOTATION

This section specifies operators that take xs:NOTATION values as arguments.

Function	Meaning
`op:NOTATION-equal`	Returns `true` if the two `xs:NOTATION` values have the same namespace URI and the same local part.

12.1 op:NOTATION-equal

Summary

Returns true if the two xs:NOTATION values have the same namespace URI and the same local part.

Operator Mapping

Defines the semantics of the eq and ne operators when applied to two values of type xs:NOTATION.

Signature

`op:NOTATION-equal`(
`$arg1`	`as` `xs:NOTATION`,
`$arg2`	`as` `xs:NOTATION`
) `as` `xs:boolean`

Rules

The function returns true if the namespace URIs of $arg1 and $arg2 are equal and the local names of $arg1 and $arg2 are equal.

Otherwise, the function returns false.

The namespace URI parts are considered equal if they are both absent^DM40, or if they are both present and equal under the rules of the fn:codepoint-equal function.

The local parts are also compared under the rules of the fn:codepoint-equal function.

Notes

The prefix parts of $arg1 and $arg2, if any, are ignored.

13 Functions and operators on nodes

This section specifies functions and operators on nodes. Nodes are formally defined in Section 6 Nodes ^DM31.

Function	Meaning
`fn:name`	Returns the name of a node, as an `xs:string` that is either the zero-length string, or has the lexical form of an `xs:QName`.
`fn:local-name`	Returns the local part of the name of `$node` as an `xs:string` that is either the zero-length string, or has the lexical form of an `xs:NCName`.
`fn:namespace-uri`	Returns the namespace URI part of the name of `$node`, as an `xs:anyURI` value.
`fn:lang`	This function tests whether the language of `$node`, or the context value if the second argument is omitted, as specified by `xml:lang` attributes is the same as, or is a sublanguage of, the language specified by `$language`.
`fn:root`	Returns the root of the tree to which `$node` belongs. This will usually, but not necessarily, be a document node.
`fn:path`	Returns a path expression that can be used to select the supplied node relative to the root of its containing document.
`fn:has-children`	Returns `true` if the supplied node has one or more child nodes (of any kind).
`fn:innermost`	Returns every node within the input sequence that is not an ancestor of another member of the input sequence; the nodes are returned in document order with duplicates eliminated.
`fn:outermost`	Returns every node within the input sequence that has no ancestor that is itself a member of the input sequence; the nodes are returned in document order with duplicates eliminated.

13.1 fn:name

Summary

Returns the name of a node, as an xs:string that is either the zero-length string, or has the lexical form of an xs:QName.

Signature

`fn:name`(
`$node`	`as` `node()?`	`:=` `.`
) `as` `xs:string`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If the argument is supplied and is the empty sequence, the function returns the zero-length string.

If the node identified by $node has no name (that is, if it is a document node, a comment, a text node, or a namespace node having no name), the function returns the zero-length string.

Otherwise, the function returns the value of the expression fn:string(fn:node-name($node)).

Error Conditions

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Notes

Because the result depends on the choice of namespace prefixes in the source document, it is not good practice to use the result of this function for anything other than display purposes. For example, the test name(.) = 'my:profile' will fail if the source document uses an unexpected namespace prefix. Such a test (assuming it relates to an element node) is better written as boolean(self::my:profile).

Examples

Variables
let $e := <doc> <p id="alpha" xml:id="beta">One</p> <p id="gamma" xmlns="http://example.com/ns">Two</p> <ex:p id="delta" xmlns:ex="http://example.com/ns">Three</ex:p> <?pi 3.14159?> </doc>

Expression	Result
`name($e//*[@id = 'alpha'])`	"p"
`name($e//*[@id = 'gamma'])`	"p"
`name($e//*[@id = 'delta'])`	"ex:p"
`name($e//processing-instruction()[1])`	"pi"
`name($e//*[@id = 'alpha']/text())`	""
`name($e//*[@id = 'alpha']/@id)`	"id"
`name($e//*[@id = 'alpha']/@xml:id`	"xml:id"

13.2 fn:local-name

Summary

Returns the local part of the name of $node as an xs:string that is either the zero-length string, or has the lexical form of an xs:NCName.

Signature

`fn:local-name`(
`$node`	`as` `node()?`	`:=` `.`
) `as` `xs:string`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If the argument is supplied and is the empty sequence, the function returns the zero-length string.

If the node identified by $node has no name (that is, if it is a document node, a comment, a text node, or a namespace node having no name), the function returns the zero-length string.

Otherwise, the function returns the local part of the expanded-QName of the node identified by $node, as determined by the dm:node-name accessor defined in Section 4.10 node-name Accessor^DM40. This will be an xs:string whose lexical form is an xs:NCName.

Error Conditions

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Examples

Variables
let $e := <doc> <p id="alpha" xml:id="beta">One</p> <p id="gamma" xmlns="http://example.com/ns">Two</p> <ex:p id="delta" xmlns:ex="http://example.com/ns">Three</ex:p> <?pi 3.14159?> </doc>

Expression	Result
`local-name($e//*[@id = 'alpha'])`	"p"
`local-name($e//*[@id = 'gamma'])`	"p"
`local-name($e//*[@id = 'delta'])`	"p"
`local-name($e//processing-instruction()[1])`	"pi"
`local-name($e//*[@id = 'alpha']/text())`	""
`local-name($e//*[@id = 'alpha']/@id)`	"id"
`local-name($e//*[@id = 'alpha']/@xml:id`	"id"

13.3 fn:namespace-uri

Summary

Returns the namespace URI part of the name of $node, as an xs:anyURI value.

Signature

`fn:namespace-uri`(
`$node`	`as` `node()?`	`:=` `.`
) `as` `xs:anyURI`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If the argument is omitted, it defaults to the context node (.). The behavior of the function if the argument is omitted is exactly the same as if the context value had been passed as the argument.

If the node identified by $node is neither an element nor an attribute node, or if it is an element or attribute node whose expanded-QName (as determined by the dm:node-name accessor in the Section 4.10 node-name Accessor^DM40) is in no namespace, then the function returns the zero-length xs:anyURI value.

Otherwise, the result will be the namespace URI part of the expanded-QName of the node identified by $node, as determined by the dm:node-name accessor defined in Section 4.10 node-name Accessor^DM40), returned as an xs:anyURI value.

Error Conditions

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Examples

Variables
let $e := <doc> <p id="alpha" xml:id="beta">One</p> <p id="gamma" xmlns="http://example.com/ns">Two</p> <ex:p id="delta" xmlns:ex="http://example.com/ns">Three</ex:p> <?pi 3.14159?> </doc>

Expression	Result
`namespace-uri($e//*[@id = 'alpha'])`	""
`namespace-uri($e//*[@id = 'gamma'])`	"http://example.com/ns"
`namespace-uri($e//*[@id = 'delta'])`	"http://example.com/ns"
`namespace-uri($e//processing-instruction()[1])`	""
`namespace-uri($e//*[@id = 'alpha']/text())`	""
`namespace-uri($e//*[@id = 'alpha']/@id)`	""
`namespace-uri($e//*[@id = 'alpha']/@xml:id)`	"http://www.w3.org/XML/1998/namespace"

13.4 fn:lang

Summary

This function tests whether the language of $node, or the context value if the second argument is omitted, as specified by xml:lang attributes is the same as, or is a sublanguage of, the language specified by $language.

Signature

`fn:lang`(
`$language`	`as` `xs:string?`,
`$node`	`as` `node()`	`:=` `.`
) `as` `xs:boolean`

Properties

The one-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The two-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The behavior of the function if the second argument is omitted is exactly the same as if the context value (.) had been passed as the second argument.

The language of the argument $node, or the context value if the second argument is omitted, is determined by the value of the xml:lang attribute on the node, or, if the node has no such attribute, by the value of the xml:lang attribute on the nearest ancestor of the node that has an xml:lang attribute. If there is no such ancestor, then the function returns false.

If $language is the empty sequence it is interpreted as the zero-length string.

The relevant xml:lang attribute is determined by the value of the XPath expression:

(ancestor-or-self::*/@xml:lang)[last()]

If this expression returns an empty sequence, the function returns false.

Otherwise, the function returns true if and only if, based on a caseless default match as specified in section 3.13 of [The Unicode Standard], either:

$language is equal to the string-value of the relevant xml:lang attribute, or
$language is equal to some substring of the string-value of the relevant xml:lang attribute that starts at the start of the string-value and ends immediately before a hyphen, - (HYPHEN-MINUS, #x002D).

Error Conditions

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Examples

The expression `fn:lang("en")` would return `true` if the context node were any of the following four elements:
`<para xml:lang="en"/>` `<div xml:lang="en"><para>And now, and forever!</para></div>` `<para xml:lang="EN"/>` `<para xml:lang="en-us"/>`
The expression `fn:lang("fr")` would return `false` if the context node were `<para xml:lang="EN"/>`

13.5 fn:root

Summary

Returns the root of the tree to which $node belongs. This will usually, but not necessarily, be a document node.

Signature

`fn:root`(
`$node`	`as` `node()?`	`:=` `.`
) `as` `node()?`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If the function is called without an argument, the context value (.) is used as the default argument. The behavior of the function if the argument is omitted is exactly the same as if the context value had been passed as the argument.

The function returns the value of the expression ($arg/ancestor-or-self::node())[1].

Error Conditions

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Examples

These examples use some variables which could be defined in [XQuery 4.1: An XML Query Language] as:
let $i := <tool>wrench</tool> let $o := <order> {$i} <quantity>5</quantity> </order> let $odoc := document {$o} let $newi := $o/tool
Or they could be defined in [XSL Transformations (XSLT) Version 4.0] as:
<xsl:variable name="i" as="element()"> <tool>wrench</tool> </xsl:variable> <xsl:variable name="o" as="element()"> <order> <xsl:copy-of select="$i"/> <quantity>5</quantity> </order> </xsl:variable> <xsl:variable name="odoc"> <xsl:copy-of select="$o"/> </xsl:variable> <xsl:variable name="newi" select="$o/tool"/>
`fn:root($i)` returns the element node `$i`
`fn:root($o/quantity)` returns the element node `$o`
`fn:root($odoc//quantity)` returns the document node `$odoc`
`fn:root($newi)` returns the element node `$o`
The final three examples could be made type-safe by wrapping their operands with `fn:exactly-one()`.

13.6 fn:path

Summary

Returns a path expression that can be used to select the supplied node relative to the root of its containing document.

Signature

`fn:path`(
`$node`	`as` `node()?`	`:=` `.`
) `as` `xs:string?`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The behavior of the function if the argument is omitted is exactly the same as if the context value (.) had been passed as the argument.

If $node is the empty sequence, the function returns the empty sequence.

If $node is a document node, the function returns the string "/".

Otherwise, the function returns a string that consists of a sequence of steps, one for each ancestor-or-self of $node other than the root node. This string is prefixed by "Q{http://www.w3.org/2005/xpath-functions}root()" if the root node is not a document node. Each step consists of the character "/" followed by a string whose form depends on the kind of node selected by that step, as follows:

For an element node, Q{uri}local[position], where uri is the namespace URI of the node name or the empty string if the node is in no namespace, local is the local part of the node name, and position is an integer representing the position of the selected node among its like-named siblings.
For an attribute node:
1. if the node is in no namespace, @local, where local is the local part of the node name
2. otherwise, @Q{uri}local, where uri is the namespace URI of the node name, and local is the local part of the node name
For a text node: text()[position] where position is an integer representing the position of the selected node among its text node siblings
For a comment node: comment()[position] where position is an integer representing the position of the selected node among its comment node siblings
For a processing-instruction node: processing-instruction(local)[position] where local is the name of the processing instruction node and position is an integer representing the position of the selected node among its like-named processing-instruction node siblings
For a namespace node:
1. If the namespace node has a name: namespace::prefix, where prefix is the local part of the name of the namespace node (which represents the namespace prefix).
2. If the namespace node has no name (that is, it represents the default namespace): namespace::*[Q{http://www.w3.org/2005/xpath-functions}local-name()=""]

Error Conditions

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Examples

Variables

let $e := 
document {            
<p xmlns="http://example.com/one" xml:lang="de" author="Friedrich von Schiller">
Freude, schöner Götterfunken,<br/>
Tochter aus Elysium,<br/>
Wir betreten feuertrunken,<br/>
Himmlische, dein Heiligtum.</p>}

let $emp := 
  <employee xml:id="ID21256">
     <empnr>E21256</empnr>
     <first>John</first>
     <last>Brown</last>
  </employee>

Expression:	`path($e)`
Result:	'/'
Expression:	`path($e/*:p)`
Result:	'/Q{http://example.com/one}p[1]'
Expression:	`path($e/*:p/@xml:lang)`
Result:	'/Q{http://example.com/one}p[1]/@Q{http://www.w3.org/XML/1998/namespace}lang'
Expression:	`path($e/*:p/@author)`
Result:	'/Q{http://example.com/one}p[1]/@author'
Expression:	`path($e/:p/:br[2])`
Result:	'/Q{http://example.com/one}p[1]/Q{http://example.com/one}br[2]'
Expression:	path( $e//text()[ starts-with(normalize-space(), 'Tochter') ] )
Result:	'/Q{http://example.com/one}p[1]/text()[2]'
Expression:	`path($emp)`
Result:	'Q{http://www.w3.org/2005/xpath-functions}root()'
Expression:	`path($emp/@xml:id)`
Result:	'Q{http://www.w3.org/2005/xpath-functions}root()/@Q{http://www.w3.org/XML/1998/namespace}id'
Expression:	`path($emp/empnr)`
Result:	'Q{http://www.w3.org/2005/xpath-functions}root()/Q{}empnr[1]'

13.7 fn:has-children

Summary

Returns true if the supplied node has one or more child nodes (of any kind).

Signature

`fn:has-children`(
`$node`	`as` `node()?`	`:=` `.`
) `as` `xs:boolean`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Provided that the supplied argument $node matches the expected type node()?, the result of the function call fn:has-children($node) is defined to be the same as the result of the expression fn:exists($node/child::node()).

Error Conditions

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Notes

If $node is an empty sequence the result is false.

The motivation for this function is to support streamed evaluation. According to the streaming rules in [XSL Transformations (XSLT) Version 4.0], the following construct is not streamable:

<xsl:if test="exists(row)">
  <ulist>
    <xsl:for-each select="row">
       <item><xsl:value-of select="."/></item>
    </xsl:for-each>
  </ulist>
</xsl:if>

This is because it makes two downward selections to read the child row elements. The use of fn:has-children in the xsl:if conditional is intended to circumvent this restriction.

Although the function was introduced to support streaming use cases, it has general utility as a convenience function.

Examples

Variables
let $e := <doc> <p id="alpha">One</p> <p/> <p>Three</p> <?pi 3.14159?> </doc>

Expression	Result
`has-children($e)`	true()
`has-children($e//p[1])`	true()
`has-children($e//p[2])`	false()
`has-children($e//p[3])`	true()
`has-children($e//processing-instruction()[1])`	false()
`has-children($e//p[1]/text())`	false()
`has-children($e//p[1]/@id)`	false()

13.8 fn:innermost

Summary

Returns every node within the input sequence that is not an ancestor of another member of the input sequence; the nodes are returned in document order with duplicates eliminated.

Signature

`fn:innermost`(
`$nodes`	`as` `node()*`
) `as` `node()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The effect of the function call fn:innermost($nodes) is defined to be equivalent to the result of the expression:

$nodes except $nodes/ancestor::node()

That is, the function takes as input a sequence of nodes, and returns every node within the sequence that is not an ancestor of another node within the sequence; the nodes are returned in document order with duplicates eliminated.

Examples

If the source document contains nested sections represented by div elements, the expression innermost(//div) returns those div elements that do not contain further div elements.

13.9 fn:outermost

Summary

Returns every node within the input sequence that has no ancestor that is itself a member of the input sequence; the nodes are returned in document order with duplicates eliminated.

Signature

`fn:outermost`(
`$nodes`	`as` `node()*`
) `as` `node()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The effect of the function call fn:outermost($nodes) is defined to be equivalent to the result of the expression:

$nodes[not(ancestor::node() intersect $nodes)]/.

That is, the function takes as input a sequence of nodes, and returns every node within the sequence that does not have another node within the sequence as an ancestor; the nodes are returned in document order with duplicates eliminated.

Notes

The formulation $nodes except $nodes/descendant::node() might appear to be simpler, but does not correctly account for attribute nodes, as these are not descendants of their parent element.

The motivation for the function was based on XSLT streaming use cases. There are cases where the [XSL Transformations (XSLT) Version 4.0] streaming rules allow the construct outermost(//section) but do not allow //section; the function can therefore be useful in cases where it is known that sections will not be nested, as well as cases where the application actually wishes to process all sections except those that are nested within another.

Examples

If the source document contains nested sections represented by div elements, the expression outermost(//div) returns those div elements that are not contained within further div elements.

14 Functions and operators on sequences

A sequence is an ordered collection of zero or more items. An item is a node, an atomic value, or a function, such as a map or an array. The terms sequence and item are defined formally in [XQuery 4.1: An XML Query Language] and [XML Path Language (XPath) 4.0].

14.1 General functions and operators on sequences

The following functions are defined on sequences. These functions work on any sequence, without performing any operations that are sensitive to the individual items in the sequence.

Function	Meaning
`fn:empty`	Returns `true` if the argument is the empty sequence.
`fn:exists`	Returns `true` if the argument is a non-empty sequence.
`fn:foot`	Returns the last item in a sequence.
`fn:head`	Returns the first item in a sequence.
`fn:identity`	Returns its argument value.
`fn:insert-before`	Returns a sequence constructed by inserting an item or a sequence of items at a given position within an existing sequence.
`fn:intersperse`	Inserts a separator between adjacent items in a sequence.
`fn:items-at`	Returns a sequence containing the items from `$input` at positions defined by `$at`, in the order specified.
`fn:remove`	Returns a new sequence containing all the items of `$input` except those at specified positions.
`fn:replicate`	Produces multiple copies of a sequence.
`fn:reverse`	Reverses the order of items in a sequence.
`fn:slice`	Returns a sequence containing selected items from a supplied input sequence based on their position.
`fn:subsequence`	Returns the contiguous sequence of items in `$input` beginning at the position indicated by `$start` and continuing for the number of items indicated by `$length`.
`fn:tail`	Returns all but the first item in a sequence.
`fn:trunk`	Returns all but the last item in a sequence.
`fn:unordered`	Returns the items of `$input` in an ·implementation-dependent· order.
`fn:void`	Absorbs the argument.

As in the previous section, for the illustrative examples below, assume an XQuery or transformation operating on a non-empty Purchase Order document containing a number of line-item elements. The variable $seq is bound to the sequence of line-item nodes in document order. The variables $item1, $item2, etc. are bound to separate, individual line-item nodes in the sequence.

14.1.1 fn:empty

Summary

Returns true if the argument is the empty sequence.

Signature

`fn:empty`(
`$input`	`as` `item()*`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $input is the empty sequence, the function returns true; otherwise, the function returns false.

Examples

Expression	Result
`empty((1,2,3)[10])`	true()
`empty(remove(("hello", "world"), 1))`	false()
`empty([])`	false()
`empty(map{})`	false()
`empty("")`	false()
Assuming `$break` is an element with no children:
let $break := <br/> return empty($break)
The result is `false()`.

14.1.2 fn:exists

Summary

Returns true if the argument is a non-empty sequence.

Signature

`fn:exists`(
`$input`	`as` `item()*`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $input is a non-empty sequence, the function returns true; otherwise, the function returns false.

Examples

Expression	Result
`exists(remove(("hello"), 1))`	false()
`exists(remove(("hello", "world"), 1))`	true()
`exists([])`	true()
`exists(map{})`	true()
`exists("")`	true()
Assuming `$break` is an element with no children:
let $break := <br/> return exists($break)
The result is `true()`.

14.1.3 fn:foot

Summary

Returns the last item in a sequence.

Signature

`fn:foot`(
`$input`	`as` `item()*`
) `as` `item()?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the value of the expression $input[last()]

Notes

If $input is the empty sequence the empty sequence is returned.

Examples

Expression	Result
`foot(1 to 5)`	(5)
`foot(())`	()

History

New in 4.0.

14.1.4 fn:head

Summary

Returns the first item in a sequence.

Signature

`fn:head`(
`$input`	`as` `item()*`
) `as` `item()?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the value of the expression $input[1]

Notes

If $input is the empty sequence, the empty sequence is returned. Otherwise the first item in the sequence is returned.

Examples

Expression	Result
`head(1 to 5)`	1
`head(("a", "b", "c"))`	"a"
`head(())`	()
`head([1,2,3])`	[1,2,3]

14.1.5 fn:identity

Summary

Returns its argument value.

Signature

`fn:identity`(
`$input`	`as` `item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns $input.

Notes

The function is useful in contexts where a function must be supplied, but no processing is required.

Examples

Expression	Result
`identity(0)`	(0)
`identity(1 to 10)`	(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
`parse-xml('<a/>') ! (identity(/) is /)`	true() (If the argument is a node, the function returns the identical node, not a copy).
`identity(())`	()

History

New in 4.0. Accepted 2022-09-20.

14.1.6 fn:insert-before

Summary

Returns a sequence constructed by inserting an item or a sequence of items at a given position within an existing sequence.

Signature

`fn:insert-before`(
`$input`	`as` `item()*`,
`$position`	`as` `xs:integer`,
`$insert`	`as` `item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The value returned by the function consists of all items of $input whose 1-based position is less than $position, followed by all items of $insert, followed by the remaining elements of $input, in that order.

Notes

If $input is the empty sequence, $insert is returned. If $insert is the empty sequence, $input is returned.

If $position is less than one (1), the first position, the effective value of $position is one (1). If $position is greater than the number of items in $input, then the effective value of $position is equal to the number of items in $input plus 1.

The value of $input is not affected by the sequence construction.

Examples

Variables
let $abc := ("a", "b", "c")

Expression	Result
`insert-before($abc, 0, "z")`	("z", "a", "b", "c")
`insert-before($abc, 1, "z")`	("z", "a", "b", "c")
`insert-before($abc, 2, "z")`	("a", "z", "b", "c")
`insert-before($abc, 3, "z")`	("a", "b", "z", "c")
`insert-before($abc, 4, "z")`	("a", "b", "c", "z")

14.1.7 fn:intersperse

Summary

Inserts a separator between adjacent items in a sequence.

Signature

`fn:intersperse`(
`$input`	`as` `item()*`,
`$separator`	`as` `item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the value of head($input), tail($input) ! ($separator, .).

Notes

If $input contains less than two items then it is returned unchanged.

If $separator is the empty sequence then $input is returned unchanged.

For example, in XQuery, fn:intersperse(para, <hr/>) would insert an empty hr element between adjacent paragraphs.

Examples

Expression	Result
`intersperse(1 to 5, "\|")`	(1, "\|", 2, "\|" , 3, "\|", 4, "\|", 5)
`intersperse((), "\|")`	()
`intersperse("A", "\|")`	"A"
`intersperse(1 to 5, ())`	(1, 2, 3, 4, 5)
`intersperse(1 to 3, ("⅓", "⅔"))`	(1, "⅓", "⅔", 2, "⅓", "⅔", 3)

History

New in 4.0. Accepted 2022-09-27.

14.1.8 fn:items-at

Summary

Returns a sequence containing the items from $input at positions defined by $at, in the order specified.

Signature

`fn:items-at`(
`$input`	`as` `item()*`,
`$at`	`as` `xs:integer*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Returns the value of $at ! fn:subsequence($input, ., 1)

Notes

The effect of the function is to return those items from $input at the positions given by the integers in $at, in the order represented by the integers in $at.

In the simplest case where $at is a single integer, fn:items-at($input, 3) returns the same result as $input[3].

Compared with a simple positional filter expression, the function is useful because:

It can select items at multiple positions, and unlike fn:subsequence, these do not need to be contiguous.
The $at expression can depend on the focus.
The order of the returned items can differ from their order in the $input sequence.

If any integer in $at is outside the range 1 to count($input), that integer is effectively ignored: no error occurs.

If either of the arguments is an empty sequence, the result is an empty sequence.

If $at contains duplicate integers, the result also contains duplicates. No de-duplication occurs. If the input sequence contains nodes, these are not copied: instead, the result sequence contains multiple references to the same node.

Examples

Expression	Result
`items-at(11 to 20, 4)`	14
`items-at(11 to 20, 4 to 6)`	14, 15, 16
`items-at(11 to 20, (7, 3))`	17, 13
`items-at(11 to 20, index-of(("a", "b", "c"), "b"))`	12
`items-at(characters("quintessential"), (4, 8, 3))`	("n", "s", "i")
`items-at(characters("quintessential"), (4, 8, 3, 1, 1))`	("n", "s", "i", "q", "q")
`items-at((), 832)`	()
`items-at((), ())`	()

History

New in 4.0 (see issue 213)

14.1.9 fn:remove

Summary

Returns a new sequence containing all the items of $input except those at specified positions.

Signature

`fn:remove`(
`$input`	`as` `item()*`,
`$positions`	`as` `xs:integer*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns a sequence consisting of all items of $input whose 1-based position is not equal to any of the integers in $positions.

More formally, the function returns the result of the expression $input[not(position() = $positions)].

Notes

Any integer in $positions that is less than 1 or greater than the number of items in $input is effectively ignored.

If $input is the empty sequence, the empty sequence is returned.

If $positions is an empty sequence, the input sequence $input is returned unchanged.

Examples

Variables
let $abc := ("a", "b", "c")

Expression	Result
`remove($abc, 0)`	("a", "b", "c")
`remove($abc, 1)`	("b", "c")
`remove($abc, 6)`	("a", "b", "c")
`remove((), 3)`	()
`remove($abc, 2 to 3)`	"a"
`remove($abc, ())`	("a", "b", "c")

History

Changed in 4.0: the second argument can now be a sequence of integers.

14.1.10 fn:replicate

Summary

Produces multiple copies of a sequence.

Signature

`fn:replicate`(
`$input`	`as` `item()*`,
`$count`	`as` `xs:nonNegativeInteger`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the value of (1 to $count) ! $input.

Notes

If $input is the empty sequence, the empty sequence is returned.

The $count argument is declared as xs:nonNegativeInteger, which means that a type error occurs if it is called with a negative value.

If the input sequence contains nodes, these are not copied: instead, the result sequence contains multiple references to the same node. So, for example, fn:count(fn:replicate(/, 6)|()) returns 1, because the fn:replicate call creates duplicates, and the union operation eliminates them.

[TODO: the use of type xs:nonNegativeInteger for the second argument assumes we will accept the proposal to allow downcasting in the coercion rules for function arguments. MHK 2022-10-04.]

Examples

Expression	Result
`replicate(0, 6)`	(0, 0, 0, 0, 0, 0)
`replicate(("A", "B", "C"), 3)`	("A", "B", "C", "A", "B", "C", "A", "B", "C")
`replicate((), 5)`	()
`replicate(("A", "B", "C"), 1)`	("A", "B", "C")
`replicate(("A", "B", "C"), 0)`	()

History

New in 4.0. Accepted 2022-10-04.

14.1.11 fn:reverse

Summary

Reverses the order of items in a sequence.

Signature

`fn:reverse`(
`$input`	`as` `item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns a sequence containing the items in $input in reverse order.

Notes

If $input is the empty sequence, the empty sequence is returned.

Examples

Variables
let $abc := ("a", "b", "c")

Expression	Result
`reverse($abc)`	("c", "b", "a")
`reverse(("hello"))`	("hello")
`reverse(())`	()
`reverse([1,2,3])`	[1,2,3] (The input is a sequence containing a single item (the array)).
`reverse(([1,2,3],[4,5,6]))`	([4,5,6],[1,2,3])

14.1.12 fn:slice

Summary

Returns a sequence containing selected items from a supplied input sequence based on their position.

Signature

`fn:slice`(
`$input`	`as` `item()*`,
`$start`	`as` `xs:integer?`	`:=` `()`,
`$end`	`as` `xs:integer?`	`:=` `()`,
`$step`	`as` `xs:integer?`	`:=` `()`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $input is the empty sequence, the function returns the empty sequence.

Let $S be the first of the following that applies:

If $start is absent, empty, or zero, then 1.
If $start is negative, then fn:count($input) + $start + 1.
Otherwise, $start.

Let $E be the first of the following that applies:

If $end is absent, empty, or zero, then fn:count($input).
If $end is negative, then fn:count($input) + $end + 1.
Otherwise, $end.

Let $STEP be the first of the following that applies:

If $step is absent, empty, or zero, then:
- If $E ge $S, then +1
- Otherwise -1
Otherwise, $step.

If $STEP is negative, the function returns $input => fn:reverse() => fn:slice(-$S, -$E, -$STEP).

Otherwise the function returns the result of the expression:

$input[position() ge $S and position() le $E and (position() - $S) mod $STEP eq 0]

Notes

The function is inspired by the slice operators in Javascript and Python, but it differs in detail to accommodate the tradition of 1-based addressing in XPath. The end position is inclusive rather than exclusive, so that in the simple case where $start and $end are positive and $end > $start, fn:slice($in, $start, $end) returns the same result as $in[position() = $start to $end].

This function can be used to enhance the RangeExpression, defined in [TITLE OF XP31 SPEC, TITLE OF id-range-expressions SECTION]^XP31, to construct a sequence of integers based on steps other than 1.

Examples

Variables
let $in := ('a', 'b', 'c', 'd', 'e')

Expression	Result
`slice($in, start := 2, end := 4)`	("b", "c", "d")
`slice($in, start := 2)`	("b", "c", "d", "e")
`slice($in, end := 2)`	("a", "b")
`slice($in, start := 3, end := 3)`	("c")
`slice($in, start := 4, end := 3)`	("d", "c")
`slice($in, start := 2, end := 5, step := 2)`	("b", "d")
`slice($in, start := 5, end := 2, step := -2)`	("e", "c")
`slice($in, start := 2, end := 5, step := -2)`	()
`slice($in, start := 5, end := 2, step := 2)`	()
`slice($in)`	("a", "b", "c", "d", "e")
`slice($in, start := -1)`	("e")
`slice($in, start := -3)`	("c", "d", "e")
`slice($in, end := -2)`	("a", "b", "c", "d")
`slice($in, start := 2, end := -2)`	("b", "c", "d")
`slice($in, start := -2, end := 2)`	("d", "c", "b")
`slice($in, start := -4, end := -2)`	("b", "c", "d")
`slice($in, start := -2, end := -4)`	("d", "c", "b")
`slice($in, start := -4, end := -2, step := 2)`	("b", "d")
`slice($in, start := -2, end := -4, step := -2)`	("d", "b")
`slice(("a", "b", "c", "d"), 0)`	("a", "b", "c", "d")
`slice((1 to 5), step := 2)`	(1, 3, 5)
`slice((1 to 5), step := -2)`	(5, 3, 1)

History

Proposed for 4.0; not yet reviewed.

14.1.13 fn:subsequence

Summary

Returns the contiguous sequence of items in $input beginning at the position indicated by $start and continuing for the number of items indicated by $length.

Signature

`fn:subsequence`(
`$input`	`as` `item()*`,
`$start`	`as` `xs:double`,
`$length`	`as` `xs:double?`	`:=` `()`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

In the two-argument case (or where the third argument is an empty sequence), the function returns:

$input[round($start) le position()]

In the three-argument case, the function returns:

$input[round($start) le position() 
         and position() lt round($start) + round($length)]

Notes

The first item of a sequence is located at position 1, not position 0.

If $input is the empty sequence, the empty sequence is returned.

In the two-argument case, the function returns a sequence comprising those items of $input whose 1-based position is greater than or equal to $start (rounded to an integer). No error occurs if $start is zero or negative.

In the three-argument case, The function returns a sequence comprising those items of $input whose 1-based position is greater than or equal to $start (rounded to an integer), and less than the sum of $start and $length (both rounded to integers). No error occurs if $start is zero or negative, or if $start plus $length exceeds the number of items in the sequence, or if $length is negative.

As a consequence of the general rules, if $start is -INF and $length is +INF, then fn:round($start) + fn:round($length) is NaN; since position() lt NaN always returns false, the result is an empty sequence.

The reason the function accepts arguments of type xs:double is that many computations on untyped data return an xs:double result; and the reason for the rounding rules is to compensate for any imprecision in these floating-point computations.

Examples

Variables
let $seq := ("item1", "item2", "item3", "item4", "item5")

Expression	Result
`subsequence($seq, 4)`	("item4", "item5")
`subsequence($seq, 3, 2)`	("item3", "item4")

14.1.14 fn:tail

Summary

Returns all but the first item in a sequence.

Signature

`fn:tail`(
`$input`	`as` `item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the value of the expression subsequence($input, 2)

Notes

If $input is the empty sequence, or a sequence containing a single item, then the empty sequence is returned.

Examples

Expression	Result
`tail(1 to 5)`	(2, 3, 4, 5)
`tail(("a", "b", "c"))`	("b", "c")
`tail("a")`	()
`tail(())`	()
`tail([1,2,3])`	()

14.1.15 fn:trunk

Summary

Returns all but the last item in a sequence.

Signature

`fn:trunk`(
`$input`	`as` `item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the value of the expression remove($input, count($input))

Notes

If $input is the empty sequence, or a sequence containing a single item, then the empty sequence is returned.

Examples

Expression	Result
`trunk(1 to 5)`	(1, 2, 3, 4)
`trunk(("a", "b", "c"))`	("a", "b")
`trunk("a")`	()
`trunk(())`	()
`trunk([1,2,3])`	()

History

New in 4.0.

14.1.16 fn:unordered

Summary

Returns the items of $input in an ·implementation-dependent· order.

Signature

`fn:unordered`(
`$input`	`as` `item()*`
) `as` `item()*`

Properties

This function is ·nondeterministic-wrt-ordering·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the items of $input in an ·implementation-dependent· order.

Notes

Query optimizers may be able to do a better job if the order of the output sequence is not specified. For example, when retrieving prices from a purchase order, if an index exists on prices, it may be more efficient to return the prices in index order rather than in document order.

This function does not guarantee that the resulting sequence will be in an order different from the input sequence. Many times the two sequences will be identical.

Examples

Expression	Result
`unordered((1, 2, 3, 4, 5))`	(1, 2, 3, 4, 5) (or some permutation thereof)

14.1.17 fn:void

Summary

Absorbs the argument.

Signature

`fn:void`(
`$input`	`as` `item()*`	`:=` `()`
) `as` `empty-sequence()`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function absorbs the supplied $input argument and returns an empty sequence.

Notes

The function can be used to discard unneeded output of expressions (functions, third-party libraries, etc.).

It can also be used to discard results during development.

The function is utilized by built-in functions such as map:get to return an empty sequence for arbitrary input.

It is ·implementation-dependent· whether the supplied argument is evaluated or ignored. An implementation may decide to evaluate ·nondeterministic· expressions and ignore deterministic ones.

Examples

Expression:	`void(1 to 1000000)`
Result:	()
Expression:	`array:get(array { 1, 2, 3 }, 4, void#1)`
Result:	() (Without the third argument, an error would be raised.)
Expression:	`for $f in (identity#1, void#1) return $f(123)`
Result:	123
Expression:	let $mapping := () return for-each(1 to 10, $mapping otherwise void#0)
Result:	() (Indicates that if no mapping is supplied, all items are dropped.)

History

New in 4.0. Approved.

14.2 Comparison functions

The functions in this section perform comparisons between the items in one or more sequences.

Function	Meaning
`fn:atomic-equal`	Determines whether two atomic values are equal, under the rules used for comparing keys in a map.
`fn:deep-equal`	This function assesses whether two sequences are deep-equal to each other. To be deep-equal, they must contain items that are pairwise deep-equal; and for two items to be deep-equal, they must either be atomic values that compare equal, or nodes of the same kind, with the same name, whose children are deep-equal, or maps with matching entries, or arrays with matching members.
`fn:compare`	Returns `-1`, `0`, or `1`, depending on whether the first value is less than, equal to, or greater than the second value.
`fn:distinct-values`	Returns the values that appear in a sequence, with duplicates eliminated.
`fn:duplicate-values`	Returns the values that appear in a sequence more than once.
`fn:index-of`	Returns a sequence of positive integers giving the positions within the sequence `$input` of items that are equal to `$search`.
`fn:starts-with-subsequence`	Determines whether one sequence starts with another, using a supplied callback function to compare items.
`fn:ends-with-subsequence`	Determines whether one sequence ends with another, using a supplied callback function to compare items.
`fn:contains-subsequence`	Determines whether one sequence contains another as a contiguous subsequence, using a supplied callback function to compare items.

14.2.1 fn:atomic-equal

Summary

Determines whether two atomic values are equal, under the rules used for comparing keys in a map.

Signature

`fn:atomic-equal`(
`$value1`	`as` `xs:anyAtomicType`,
`$value2`	`as` `xs:anyAtomicType`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function fn:atomic-equal is used to compare two atomic values for equality. This function has the following properties (which do not all apply to the eq operator):

Any two atomic values can be compared, regardless of their type.
No dynamic error is ever raised (the result is either true or false).
The result of the comparison never depends on the static or dynamic context.
Every value (including NaN) is equal to itself.
The comparison is symmetric: if A equals B, then B equals A.
The comparison is transitive: if A equals B and B equals C, then A equals C.

The function returns true if and only if one of the following conditions is true:

All of the following conditions are true:
1. $value1 is an instance of xs:string, xs:anyURI, or xs:untypedAtomic
2. $value2 is an instance of xs:string, xs:anyURI, or xs:untypedAtomic
3. fn:codepoint-equal($value1, $value2)
Note:

Strings are compared without any dependency on collations.
All of the following conditions are true:
1. $value1 is an instance of xs:decimal, xs:double, or xs:float
2. $value2 is an instance of xs:decimal, xs:double, or xs:float
3. One of the following conditions is true:
  1. Both $value1 and $value2 are NaN
    
    Note:
    
    xs:double('NaN') is the same key as xs:float('NaN')
  2. Both $value1 and $value2 are positive infinity
    
    Note:
    
    xs:double('INF') is the same key as xs:float('INF')
  3. Both $value1 and $value2 are negative infinity
    
    Note:
    
    xs:double('-INF') is the same key as xs:float('-INF')
  4. $value1 and $value2 when converted to decimal numbers with no rounding or loss of precision are mathematically equal.
    
    Note:
    
    Every instance of xs:double, xs:float, and xs:decimal can be represented exactly as a decimal number provided enough digits are available both before and after the decimal point. Unlike the eq relation, which converts both operands to xs:double values, possibly losing precision in the process, this comparison is transitive.
    
    Note:
    
    Positive and negative zero compare equal.
All of the following conditions are true:
1. One of the following conditions is true:
  1. $value1 and $value2 are both instances of xs:date.
  2. $value1 and $value2 are both instances of xs:time.
  3. $value1 and $value2 are both instances of xs:dateTime.
  4. $value1 and $value2 are both instances of xs:gYear.
  5. $value1 and $value2 are both instances of xs:gYearMonth.
  6. $value1 and $value2 are both instances of xs:gMonth.
  7. $value1 and $value2 are both instances of xs:gMonthDay.
  8. $value1 and $value2 are both instances of xs:gDay.
2. One of the following conditions is true:
  1. Both $value1 and $value2 have a timezone
  2. Neither $value1 nor $value2 has a timezone
3. $value1 eq $value2
Note:

Values having a timezone are never equal to values without one. The implicit timezone is not used.
All of the following conditions are true:
1. One of the following conditions is true:
  1. $value1 and $value2 are both instances of xs:boolean.
  2. $value1 and $value2 are both instances of xs:QName.
  3. $value1 and $value2 are both instances of xs:NOTATION.
  4. $value1 and $value2 are both instances of xs:duration.
  5. $value1 and $value2 are both instances of xs:hexBinary.
  6. $value1 and $value2 are both instances of xs:base64Binary.
2. $value1 eq $value2

Notes

The internal function op:same-key was introduced in an earlier version of this specification for comparing keys within a map. In this version of the specification, the functionality is unchanged, but the function is exposed so that it is available directly to applications.

The function is used to assess whether two atomic values are considered to be duplicates when used as keys in a map. A map cannot contain two separate entries whose keys are the same as defined by this function. The function is also used when matching keys in functions such as map:get and map:remove.

The rules for comparing keys in a map are chosen to ensure that the comparison is:

Context-free: there is no dependency on the static or dynamic context
Error-free: any two atomic values can be compared, and the result is either true or false, never an error
Transitive: if A is the same key as B, and B is the same key as C, then A is the same key as C.

Two atomic values may be distinguishable even though they are equal under this comparison. For example: they may have different type annotations; dates and times may have different timezones; xs:QName values may have different prefixes.

Unlike the eq operator and the fn:deep-equal function, xs:hexBinary and xs:base64Binary values are considered distinct. This decision was made in order to preserve backwards compatibility: if the values were treated as interchangeable, it would become impossible to construct certain maps that could be validly constructed using earlier versions of the specification, and it would be difficult to make maps fully interoperable between processors supporting different language versions, for example when calling fn:transform.

As always, any algorithm that delivers the right result is acceptable. For example, when testing whether an xs:double value D is the same key as an xs:decimal value that has N significant digits, it is not necessary to know all the digits in the decimal expansion of D to establish the result: computing the first N+1 significant digits (or indeed, simply knowing that there are more than N significant digits) is sufficient.

Examples

Expression:	`atomic-equal(3, 3)`
Result:	true()
Expression:	`atomic-equal(3, 3e0)`
Result:	true()
Expression:	`atomic-equal(3.1, 3.1e0)`
Result:	false()
Expression:	`atomic-equal(xs:double('NaN'), xs:float('NaN'))`
Result:	true()
Expression:	`atomic-equal("a", "a")`
Result:	true()
Expression:	`atomic-equal("a", "A")`
Result:	false()
Expression:	`atomic-equal("a", xs:untypedAtomic("a"))`
Result:	true()
Expression:	atomic-equal( "https://www.w3.org/", xs:anyURI("https://www.w3.org/") )
Result:	true()
Expression:	`atomic-equal(12, "12")`
Result:	false()

History

Proposed for 4.0; the function is identical to the internal op:same-key function in 3.1

14.2.2 fn:deep-equal

Summary

This function assesses whether two sequences are deep-equal to each other. To be deep-equal, they must contain items that are pairwise deep-equal; and for two items to be deep-equal, they must either be atomic values that compare equal, or nodes of the same kind, with the same name, whose children are deep-equal, or maps with matching entries, or arrays with matching members.

Signature

`fn:deep-equal`(
`$input1`	`as` `item()*`,
`$input2`	`as` `item()*`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `xs:boolean`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and implicit timezone.

The three-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI, and implicit timezone.

The four-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI, and implicit timezone.

Rules

The $collation argument identifies a collation which is used at all levels of recursion when strings are compared (but not when names are compared), according to the rules in 5.3.5 Choosing a collation. If the argument is not supplied, or if it is empty, then the default collation from the dynamic context of the caller is used.

The $options argument, if present, defines additional parameters controlling how the comparison is done. The ·option parameter conventions· apply.

If the two sequences are both empty, the function returns true.

If the two sequences are of different lengths, the function returns false.

If the two sequences are of the same length, the comparison is controlled by the ordered option:

By default, the option is true: The function returns true if and only if every item in the sequence $input1 is deep-equal to the item at the same position in the sequence $input2.
If the option is set to false, the function returns false if and only if every item in the sequence $input1 is deep-equal to an item at some position in the sequence $input2, and vice versa.

The rules for deciding whether two items are deep-equal appear below.

The entries that may appear in the $options map are as follows. The detailed rules for the interpretation of each option appear later.

Key	Meaning
`base-uri`	Determines whether the `base-uri` of a node is significant. Type: `xs:boolean` Default: `false`
`comments`	Determines whether comments are significant. Type: `xs:boolean` Default: `false`
`debug`	Requests diagnostics in the case where the function returns `false`. When this option is set and the two inputs are found to be not equal, the implementation should output messages (in an implementation-dependent format and to an implementation-dependent destination) indicating the nature of the differences that were found. Type: `xs:boolean` Default: `false`
`id-property`	Determines whether the `id` property of elements and attributes is significant. Type: `xs:boolean` Default: `false`
`idrefs-property`	Determines whether the `idrefs` property of elements and attributes is significant. Type: `xs:boolean` Default: `false`
`in-scope-namespaces`	Determines whether the in-scope namespaces of elements are significant. Type: `xs:boolean` Default: `false`
`namespace-prefixes`	Determines whether namespace prefixes in `xs:QName` values (particularly the names of elements and attributes) are significant. Type: `xs:boolean` Default: `false`
`nilled-property`	Determines whether the `nilled` property of elements and attributes is significant. Type: `xs:boolean` Default: `false`
`normalization-form`	If present, indicates that text and attributes are converted to the specified Unicode normalization form prior to comparison. The value is as for the corresponding argument of `fn:normalize-unicode`. Type: `xs:string?` Default: `()`
`orderd`	Controls whether the top-level order of the items of the input sequences is considered. Type: `xs:boolean` Default: `true`
`processing-instructions`	Determines whether processing instructions are significant. Type: `xs:boolean` Default: `false`
`timezones`	Determines whether timezones in date/time values are significant. Type: `xs:boolean` Default: `false`
`type-annotations`	Determines whether type annotations are significant. Type: `xs:boolean` Default: `false`
`type-variety`	Determines whether the variety of the type annotation of an element (whether it has complex content or simple content) is significant. Type: `xs:boolean` Default: `true`
`typed-values`	Determines whether nodes are compared using their typed values rather than their string values. Type: `xs:boolean` Default: `true`
`unordered-elements`	A list of QNames of elements considered to be unordered: that is, their child elements may appear in any order. Type: `xs:QName` Default:* `()`
`whitespace`	Determines the extent to which whitespace is treated as significant. The value `preserve` retains all whitespace. The value `strip` ignores text nodes consisting entirely of whitespace. The value `normalize` ignores whitespace text nodes in the same way as the `strip` option, and additionally compares text and attribute nodes after normalizing whitespace in accordance with the rules of the `fn:normalize-space` function. The detailed rules, given below, also take into account type annotations and `xml:space` attributes. Type: `enum("preserve", "strip", "normalize")` Default: `preserve`

Note:

As a general rule for boolean options (but not invariably), the value true indicates that the comparison is more strict.

In the following rules, where a recursive call on fn:deep-equal is made, this is assumed to use the same values of $collation and $options as the original call.

The rules reference a function equal-strings which compares two strings as follows:

If the whitespace option is set to normalize, then each string is processed by calling the fn:normalize-space function.
If the normalization-form option is present, each string is then normalized by calling the fn:normalize-unicode function, supplying the specified normalization form.
The two strings are then compared for equality under the requested $collation.

More formally, the equal-strings function is equivalent to the following implementation in XQuery:

declare function equal-strings(
  $string1   as xs:string,
  $string2   as xs:string, 
  $collation as xs:string,
  $options   as map(*)
) as xs:boolean {
  let $n1 := if ($options?whitespace = "normalize"))
             then normalize-unicode(?, $options?normalization-form) 
             else identity#1
  let $n2 := if ($options?normalize-space)
             then normalize-space#1 
             else identity#1               
  return compare($n1($n2($string1)), $n1($n2($string2)), $collation) eq 0    
}

The rules for deciding whether two items $i1 and $i2 are deep-equal are as follows. The two items are deep-equal if one or more of the following conditions are true:

All of the following conditions are true:
1. $i1 is an atomic value.
2. $i2 is an atomic value.
3. Either the type-annotations option is false, or both atomic values have the same type annotation.
4. One of the following conditions is true:
  1. If both $i1 and $i2 are instances of xs:string or xs:untypedAtomic, equal-strings($i1, $i2, $collation, $options) returns true.
  2. If both $i1 and $i2 are instances of xs:date, xs:time or xs:dateTime, $i1 eq $i2 returns true.
  3. If both $i1 and $i2 are instances of xs:hexBinary or xs:base64Binary, $i1 eq $i2 returns true.
  4. Otherwise, fn:atomic-equal($i1, $i2) returns true.
  Note:
  
  If $i1 and $i2 are not comparable, that is, if the expression ($i1 eq $i2) would raise an error, then the function returns false; it does not report an error.
5. One of the following conditions is true:
  1. Option namespace-prefixes is false.
  2. Neither $i1 nor $i2 is of type xs:QName or xs:NOTATION.
  3. $i1 and $i2 are qualified names with the same namespace prefix.
6. One of the following conditions is true:
  1. Option timezones is false.
  2. Neither $i1 nor $i2 is of type xs:date, xs:time, xs:dateTime, xs:gYear, xs:gYearMonth, xs:gMonth, xs:gMonthDay, or xs:gDay.
  3. Neither $i1 nor $i2 has a timezone component.
  4. Both $i1 and $i2 have a timezone component and the timezone components are equal.
All of the following conditions are true:
1. $i1 is a map.
2. $i2 is a map.
3. Both maps have the same number of entries.
4. For every entry in the first map, there is an entry in the second map that:
  1. has the ·same key· (note that the collation is not used when comparing keys), and
  2. has the same associated value (compared using the fn:deep-equal function, recursively).
All the following conditions are true:
1. $i1 is an array.
2. $i2 is an array.
3. Both arrays have the same number of members (array:size($i1) eq array:size($i2)).
4. Members in the same position of both arrays are deep-equal to each other: that is, every $p in 1 to array:size($i1) satisfies deep-equal($i1($p), $i2($p), $collation, $options).
All the following conditions are true:
1. $i1 is a function item and is not a map or array.
2. $i2 is a function item and is not a map or array.
3. $i1 and $i2 have the same function identity. The concept of function identity is explained in Section 2.9.4 Function Items^DM40.
All the following conditions are true:
1. $i1 is a node.
2. $i2 is a node.
3. Both nodes have the same node kind.
4. Either the base-uri option is false, or both nodes have the same value for their base URI property, or both nodes have an absent base URI.
5. Let significant-children($parent) be the sequence of nodes obtained by applying the following steps to the children of $parent, in turn:
  1. Comment nodes are discarded if the option comments is false.
  2. Processing instruction nodes are discarded if the option processing-instructions is false.
  3. Adjacent text nodes are merged.
  4. Whitespace-only text nodes are discarded if both the following conditions are true:
    1. Either:
      1. The option whitespace is set to strip or normalize; or
      2. $parent is a schema-validated element node whose type annotation is a complex type with an element-only or empty content model.
    2. The text node is not within the scope of an element that has the attribute xml:space="preserve".
6. One of the following conditions is true.
  1. Both nodes are document nodes, and the sequence significant-children($i1) is deep-equal to the sequence significant-children($i2).
  2. Both nodes are element nodes, and all the following conditions are true:
    1. The two nodes have the same name, that is (node-name($i1) eq node-name($i2)).
    2. Either the option namespace-prefixes is false, or both element names have the same prefix.
    3. Either the option in-scope-namespaces is false, or both element nodes have the same in-scope namespace bindings.
    4. Either the option type-annotations is false, or both element nodes have the same type annotation.
    5. Either the option id-property is false, or both element nodes have the same value for their is-id property.
    6. Either the option idrefs-property is false, or both element nodes have the same value for their is-idrefs property.
    7. Either the option nilled-property is false, or both element nodes have the same value for their nilled property.
    8. One of the following conditions is true:
      1. The option type-variety is false.
      2. Both nodes are annotated as having simple content. For this purpose simple content means either a simple type or a complex type with simple content.
      3. Both nodes are annotated as having complex content. For this purpose complex content means a complex type whose variety is mixed, element-only, or empty.
      Note:
      
      It is a consequence of this rule that, by default, validating a document D against a schema will usually (but not necessarily) result in a document that is not deep-equal to D. The exception is when the schema allows all elements to have mixed content.
    9. The two nodes have the same number of attributes, and for every attribute $a1 in $i1/@* there exists an attribute $a2 in $i2/@* such that $a1 and $a2 are deep-equal.
    10. One of the following conditions holds:
      1. Both element nodes are annotated as having simple content (as defined above), the typed-values option is true, and the typed value of $i1 is deep-equal to the typed value of $i2.
        
        Note:
        
        The typed value of an element node is used only when the element has simple content, which means that no error can occur as a result of atomizing a node with no typed value.
      2. Both element nodes are annotated as having simple content (as defined above), the typed-values option is false, and the equal-strings function returns true when applied to the string value of $i1 and the string value of $i2.
      3. Both element nodes have a type annotation that is a complex type with element-only, mixed, or empty content, the (common) element name is not present in the unordered-elements option, and the sequence significant-children($i1) is deep-equal to the sequence significant-children($i2).
      4. Both element nodes have a type annotation that is a complex type with element-only, mixed, or empty content, the (common) element name is present in the unordered-elements option, and the sequence significant-children($i1) is deep-equal to some permutation of the sequence significant-children($i2).
        
        Note:
        
        Elements annotated as xs:untyped fall into this category.
        
        Including an element name in the unordered-elements list is unlikely to be useful except when the relevant elements have element-only content, but this is not a requirement: the rules apply equally to elements with mixed content, or even (trivially) to elements with empty content.
  3. Both nodes are attribute nodes, and all the following conditions are true:
    1. The two attribute nodes have the same name, that is (node-name($i1) eq node-name($i2)).
    2. Either the option namespace-prefixes is false, or both attribute names have the same prefix.
    3. Either the option type-annotations is false, or both attribute nodes have the same type annotation.
    4. Either the option id-property is false, or both attribute nodes have the same value for their is-id property.
    5. Either the option idrefs-property is false, or both attribute nodes have the same value for their is-idrefs property.
    6. Either the option typed-value is false, or the typed value of $i1 is deep-equal to the typed value of $i2.
    7. Either the option typed-value is true, or the equal-strings function returns true when applied to the string value of $i1 and the string value of $i2.
  4. Both nodes are processing instruction nodes, and all the following conditions are true:
    1. The two nodes have the same name, that is (node-name($i1) eq node-name($i2)).
    2. The equal-strings function returns true when applied to the string value of $i1 and the string value of $i2.
  5. Both nodes are namespace nodes, and all the following conditions are true:
    1. The two nodes either have the same name or are both nameless, that is fn:deep-equal(node-name($i1), node-name($i2)).
    2. The string value of $i1 is equal to the string value of $i2 when compared using the Unicode codepoint collation.
    Note:
    
    Namespace nodes are not considered directly unless they appear in the top-level sequences passed explicitly to the fn:deep-equal function.
  6. Both nodes are comment nodes, and the equal-strings function returns true when applied to their string values.
  7. Both nodes are text nodes, and the equal-strings function returns true when applied to their string values.

In all other cases the result is false.

Error Conditions

A type error is raised [err:XPTY0004]^XP if the value of $options includes an entry whose key is defined in this specification, and whose value is not of the permitted type for that key.

A dynamic error is raised [err:FOJS0005] if the value of $options includes an entry whose key is defined in this specification, and whose value is not a permitted value for that key.

Notes

By default, whitespace in text nodes and attributes is considered significant. There are various ways whitespace differences can be ignored:

If nodes have been schema-validated, setting the typed-values option to true causes the typed values rather than the string values to be compared. This will typically cause whitespace to be ignored except where the type of the value is xs:string.
Setting the whitespace option to normalize causes all text and attribute nodes to have leading and trailing whitespace removed, and intermediate whitespace reduced to a single character.

By default, two nodes are not required to have the same type annotation, and they are not required to have the same in-scope namespaces. They may also differ in their parent, their base URI, and the values returned by the is-id and is-idrefs accessors (see Section 4.5 is-id Accessor^DM40 and Section 4.6 is-idrefs Accessor^DM40). The order of children is significant, but the order of attributes is insignificant.

By default, the contents of comments and processing instructions are significant only if these nodes appear directly as items in the two sequences being compared. The content of a comment or processing instruction that appears as a descendant of an item in one of the sequences being compared does not affect the result. In previous versions of this specification, the presence of a comment or processing instruction, if it caused text to be split across two text nodes, might affect the result; this has been changed in 4.0 so that adjacent text nodes are merged after comments and processing instructions have been stripped.

Comparing items of different kind (for example, comparing an atomic value to a node, or a map to an array, or an integer to an xs:date) returns false, it does not return an error. So the result of fn:deep-equal(1, current-dateTime()) is false.

Examples

Variables
let $at := <attendees> <name last="Parker" first="Peter"/> <name last="Barker" first="Bob"/> <name last="Parker" first="Peter"/> </attendees>

Expression:	`deep-equal($at, $at/*)`
Result:	false()
Expression:	`deep-equal($at/name[1], $at/name[2])`
Result:	false()
Expression:	`deep-equal($at/name[1], $at/name[3])`
Result:	true()
Expression:	`deep-equal($at/name[1], 'Peter Parker')`
Result:	false()
Expression:	`deep-equal([1, 2, 3], [1, 2, 3])`
Result:	true()
Expression:	`deep-equal((1, 2, 3), [1, 2, 3])`
Result:	false()
Expression:	deep-equal( map { 1: 'a', 2: 'b' }, map { 2: 'b', 1: 'a' } )
Result:	true()
Expression:	deep-equal( (1, 2, 3, 4), (1, 4, 3, 2), options := map { 'ordered': false() } )
Result:	true()
Expression:	deep-equal( (1, 1, 2, 3), (1, 2, 3, 3), options := map { 'ordered': false() } )
Result:	false()
Expression:	deep-equal( parse-xml("<a xmlns='AA'/>"), parse-xml("<p:a xmlns:p='AA'/>") )
Result:	true() (By default, namespace prefixes are ignored).
Expression:	deep-equal( parse-xml("<a xmlns='AA'/>"), parse-xml("<p:a xmlns:p='AA'/>"), options := map { 'namespace-prefixes': true() } )
Result:	false() (False because the namespace prefixes differ).
Expression:	deep-equal( parse-xml("<a xmlns='AA'/>"), parse-xml("<p:a xmlns:p='AA'/>"), options := map { 'in-scope-namespaces': true() } )
Result:	false() (False because the in-scope namespace bindings differ).
Expression:	deep-equal( parse-xml("<a><b/><c/></a>"), parse-xml("<a><c/><b/></a>") )
Result:	false() (By default, order of elements is significant).
Expression:	deep-equal( parse-xml("<a><b/><c/></a>"), parse-xml("<a><c/><b/></a>"), options := map {'unordered-elements': xs:QName('a') } )
Result:	true() (The `unordered-elements` option means that the ordering of the children of `a` is ignored.)
Expression:	deep-equal( parse-xml("<para style='bold'><span>x</span></para>"), parse-xml("<para style=' bold'> <span>x</span></para>") )
Result:	false() (By default, both the leading whitespace in the `style` attribute and the whitespace text node preceding the `span` element are significant.)
Expression:	deep-equal( parse-xml("<para style='bold'><span>x</span></para>"), parse-xml("<para style=' bold'> <span>x</span></para>"), options := map { 'whitespace': 'normalize' } )
Result:	true() (The `whitespace` option causes both the leading space in the attribute value and the whitespace preceding the `span` element to be ignored.)

History

Changed in 4.0: Options parameter added. Approved in principle on 2023-01-31, subject to further review.

14.2.3 fn:compare

Summary

Returns -1, 0, or 1, depending on whether the first value is less than, equal to, or greater than the second value.

Signature

`fn:compare`(
`$value1`	`as` `xs:anyAtomicType?`,
`$value2`	`as` `xs:anyAtomicType?`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:integer?`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

The three-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI.

Rules

Compares two atomic values $value1 and $value2 for order, and returns the integer value -1, 0, or 1, depending on whether $value1 is less than, equal to, or greater than $value2, respectively.

This function differs from the operators lt, eq, and gt in that decimal values are not converted to doubles. This means that the comparison is fully transitive, which makes it safe for use in sorting algorithms. It is used to underpin sorting in XQuery 4.0 and XSLT 4.0, and is also available as a free-standing function in its own right.

If either $value1 or $value2 is the empty sequence, the function returns the empty sequence.

Otherwise, the result is determined as follows:

If $value1 is an instance of xs:string, xs:anyURI or xs:untypedAtomic, and if $value2 is an instance of xs:string, xs:anyURI or xs:untypedAtomic, the values are compared as strings, and the result reflects the order according to the rules of the collation that is used.

The collation is determined according to the rules in 5.3.5 Choosing a collation.

When used with the default collation, the function defines the semantics of the eq, ne, gt, lt, le and ge operators on xs:string values.
If both $value1 and $value2 are instances of xs:numeric, the function relies on a total order, which is defined as follows:
1. A value $f of type xs:float is in all cases equal to the value xs:double($f). The remaining rules therefore only consider instances of xs:double and xs:decimal.
2. NaN is equal to itself and less than any other value.
3. Negative infinity is equal to itself and less than any other value except NaN.
4. Positive infinity is equal to itself and greater than any other value.
5. Negative zero is equal to positive zero.
6. Other xs:double and xs:decimal values (that is, values other than the infinities, NaN, and negative zero) are ordered according to their mathematical magnitude, the comparison being done without any rounding or loss of precision. This effect can be achieved by converting xs:double values to xs:decimal using an implementation of xs:decimal that imposes no limits on precision or scale, or an implementation whose limits are such that all xs:double values can be represented precisely.
If both $value1 and $value2 are instances of xs:boolean, then:
1. -1 is returned if op:boolean-less-than($value1, $value2) returns true.
2. 0 is returned if op:boolean-equal($value1, $value2) returns true.
3. 1 is returned otherwise.
If $value1 is an instance of xs:hexBinary or xs:base64Binary, and if $value2 is an instance of xs:hexBinary or xs:base64Binary, then:
1. -1 is returned if op:binary-less-than($value1, $value2) returns true.
2. 0 is returned if op:binary-equal($value1, $value2) returns true.
3. 1 is returned otherwise.
If both $value1 and $value2 are instances of xs:date, then:
1. -1 is returned if op:date-less-than($value1, $value2) returns true.
2. 0 is returned if op:date-equal($value1, $value2) returns true.
3. 1 is returned otherwise.
If both $value1 and $value2 are instances of xs:time, then:
1. -1 is returned if op:time-less-than($value1, $value2) returns true.
2. 0 is returned if op:time-equal($value1, $value2) returns true.
3. 1 is returned otherwise.
If both $value1 and $value2 are instances of xs:dateTime, then:
1. -1 is returned if op:dateTime-less-than($value1, $value2) returns true.
2. 0 is returned if op:dateTime-equal($value1, $value2) returns true.
3. 1 is returned otherwise.
If both $value1 and $value2 are instances of xs:dayTimeDuration, then:
1. -1 is returned if op:dayTimeDuration-less-than($value1, $value2) returns true.
2. 0 is returned if op:duration-equal($value1, $value2) returns true.
3. 1 is returned otherwise.
If both $value1 and $value2 are instances of xs:yearMonthDuration, then:
1. -1 is returned if op:yearMonthDuration-less-than($value1, $value2) returns true.
2. 0 is returned if op:duration-equal($value1, $value2) returns true.
3. 1 is returned otherwise.
For any other combination of types, a type error [err:XPTY0004]^XP is raised.

Notes

For numeric values, consider the xs:double value written as 0.1e0 and the xs:decimal value written as 0.1: The mathematical magnitude of this xs:double value is 0.1000000000000000055511151231257827021181583404541015625. Therefore, compare(0.1e0, 0.1) returns +1. By contrast, 0.1e0 lt 0.1 is false and 0.1e0 eq 0.1 is true, because those expressions convert the xs:decimal value 0.1 to the xs:double value 0.1e0 before the comparison.

Although operations such as sorting and the fn:min and fn:max functions invoke fn:compare to perform numeric comparison, these functions in some cases treat NaN differently.

Examples

Expression:	`compare('abc', 'abc')`
Result:	0
Expression:	`compare('Strasse', 'Straße')`
Result:	-1
Expression:	`compare('Strasse', 'Straße')`
Result:	0 (Assuming the default collation equates “ss” and the German letter “ß”.)
Expression:	compare( 'Strasse', 'Straße', 'http://www.w3.org/2013/collation/UCA?lang=de;strength=primary' )
Result:	0 (The specified collation equates “ss” and the German letter “ß”.)
Expression:	`compare('text', parse-xml('<xml>text</xml>'))`
Result:	0
Expression:	`compare(9, 10)`
Result:	-1
Expression:	`compare(123, 123.0)`
Result:	0
Expression:	`compare(xs:double('NaN'), xs:float('NaN'))`
Result:	0
Expression:	`compare(xs:double('NaN'), xs:double('-INF'))`
Result:	-1
Expression:	`compare(xs:double('-INF'), -23)`
Result:	-1
Expression:	`compare(1, 1e0)`
Result:	0
Expression:	`compare(1.1, 1.1e0)`
Result:	-1
Expression:	`compare(1.2, 1.2e0)`
Result:	+1
Expression:	`compare(9999, xs:double('INF'))`
Result:	-1
Expression:	`compare(false(), true())`
Result:	-1
Expression:	`compare(xs:hexBinary(''), xs:base64Binary(''))`
Result:	0
Expression:	`compare(xs:time('23:59:59'), xs:time('00:00:00'))`
Result:	1
Expression:	`compare(xs:date('2001-01-01+01:00'), xs:date('2001-01-01+00:00'))`
Result:	-1

History

Changed in 4.0: Enhanced to accept types other than strings.

14.2.4 fn:distinct-values

Summary

Returns the values that appear in a sequence, with duplicates eliminated.

Signature

`fn:distinct-values`(
`$values`	`as` `xs:anyAtomicType*`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:anyAtomicType*`

Properties

The one-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and implicit timezone.

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI, and implicit timezone.

Rules

The function returns the sequence that results from removing from $values all but one of a set of values that are considered equal to one another. Two items $J and $K in the input sequence (after atomization, as required by the function signature) are considered equal if fn:deep-equal($J, $K, $coll) is true, where $coll is the collation selected according to the rules in 5.3.5 Choosing a collation. This collation is used when string comparison is required.

If ordering mode (in the static context) is ordered then:

For any set of values that compare equal, the one that is returned is the one that appears first in $values.
The items that are returned appear in the order in which they occur within $values.

By contrast, if ordering mode is unordered then:

For any set of values that compare equal, the one that is returned is ·implementation-dependent·.
The order in which the sequence of values is returned is ·implementation-dependent·.

If the input sequence contains values of different numeric types that differ from each other by small amounts, then the eq operator is not transitive, because of rounding effects occurring during type promotion. In the situation where the input contains three values A, B, and C such that A eq B, B eq C, but A ne C, then the number of items in the result of the function (as well as the choice of which items are returned) is ·implementation-dependent·, subject only to the constraints that (a) no two items in the result sequence compare equal to each other, and (b) every input item that does not appear in the result sequence compares equal to some item that does appear in the result sequence.

For example, this arises when computing:

    distinct-values(
            (xs:float('1.0'),
            xs:decimal('1.0000000000100000000001',
            xs:double('1.00000000001'))

because the values of type xs:float and xs:double both compare equal to the value of type xs:decimal but not equal to each other.

Notes

If $values is the empty sequence, the function returns the empty sequence.

Values of type xs:untypedAtomic are compared as if they were of type xs:string.

Values that cannot be compared, because the eq operator is not defined for their types, are considered to be distinct.

For xs:float and xs:double values, positive zero is equal to negative zero and, although NaN does not equal itself, if $values contains multiple NaN values a single NaN is returned.

If xs:dateTime, xs:date or xs:time values do not have a timezone, they are considered to have the implicit timezone provided by the dynamic context for the purpose of comparison. Note that xs:dateTime, xs:date or xs:time values can compare equal even if their timezones are different.

Examples

Expression	Result
`distinct-values((1, 2.0, 3, 2))`	(1, 2.0, 3) (Assuming ordering mode is `ordered`.)
distinct-values(( xs:untypedAtomic("cherry"), xs:untypedAtomic("plum"), xs:untypedAtomic("plum") ))	(xs:untypedAtomic("cherry"), xs:untypedAtomic("plum")) (Assuming ordering mode is `ordered`.)

History

Changed in 4.0 (a) to use transitive equality comparisons for numeric values, (b) to prescribe the order of results unless ordering mode is unordered.

14.2.5 fn:duplicate-values

Summary

Returns the values that appear in a sequence more than once.

Signature

`fn:duplicate-values`(
`$values`	`as` `xs:anyAtomicType*`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:anyAtomicType*`

Properties

The one-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and implicit timezone.

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI, and implicit timezone.

Rules

The items of $values are compared against each other, according to the rules of fn:distinct-values and with $coll as the collation selected according to the rules in 5.3.5 Choosing a collation.

From each resulting set of values that are considered equal, one value will be returned if the set contains more than one value.

If ordering mode (in the static context) is ordered then:

For any set of values that compare equal, the one that is returned is the one that appears first in $values.
The items that are returned appear in the order in which they occur within $values.

By contrast, if ordering mode is unordered then:

For any set of values that compare equal, the one that is returned is ·implementation-dependent·.
The order in which the sequence of values is returned is ·implementation-dependent·.

Notes

The effect of the function is equivalent to the following XSLT expression:

<xsl:for-each-group select="$values" group-by="." collation="{$collation}">
  <xsl:sequence select="current-group()[2]"/>
</xsl:for-each>

The following XQuery expression is equivalent if no collation is specified (group by requires collation URIs to be static):

for $group in $values
group by $value := $group
where count($group) > 1
return $value

Examples

Expression:	`duplicate-values((1, 2, 3, 1.0, 1e0))`
Result:	1 (If ordering mode is `ordered` the result will be the `xs:integer` value 1.)
Expression:	`duplicate-values(1 to 100)`
Result:	()
Expression:	`duplicate-values(('1', <x>1</x>, '2', 2))`
Result:	"1" (The string `"1"` and the untyped value of the element node are considered equal, whereas the string `"2"` and the integer are considered unequal.)
Raise an error for duplicates in an ID sequence:
let $ids := duplicate-values(//@id) where exists($ids) return error((), 'Duplicate IDs found: ' \|\| string-join($ids, ', '))

14.2.6 fn:index-of

Summary

Returns a sequence of positive integers giving the positions within the sequence $input of items that are equal to $search.

Signature

`fn:index-of`(
`$input`	`as` `xs:anyAtomicType*`,
`$search`	`as` `xs:anyAtomicType`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:integer*`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and implicit timezone.

The three-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI, and implicit timezone.

Rules

The function returns a sequence of positive integers giving the positions within the sequence $input of items that are equal to $search.

The collation used by this function is determined according to the rules in 5.3.5 Choosing a collation. This collation is used when string comparison is required.

The items in the sequence $input are compared with $search under the rules for the eq operator. Values of type xs:untypedAtomic are compared as if they were of type xs:string. Values that cannot be compared, because the eq operator is not defined for their types, are considered to be distinct. If an item compares equal, then the position of that item in the sequence $input is included in the result.

The first item in a sequence is at position 1, not position 0.

The result sequence is in ascending numeric order.

Notes

If $input is the empty sequence, or if no item in $input matches $search, then the function returns the empty sequence.

No error occurs if non-comparable values are encountered. So when comparing two atomic values, the effective boolean value of fn:index-of($a, $b) is true if $a and $b are equal, false if they are not equal or not comparable.

Examples

Expression:	`index-of((10, 20, 30, 40), 35)`
Result:	()
Expression:	`index-of((10, 20, 30, 30, 20, 10), 20)`
Result:	(2, 5)
Expression:	index-of( ("a", "sport", "and", "a", "pastime"), "a" )
Result:	(1, 4)
Expression:	index-of( ("a", "b", "c"), "B", "http://www.w3.org/2005/xpath-functions/collation/html-ascii-case-insensitive" )
Result:	2
Expression:	`index-of(current-date(), 23)`
Result:	()
Expression:	`index-of([1, [5, 6], [6, 7]], 6)`
Result:	(3, 4) (The array is atomized to a sequence of five integers).
If `@a` is an attribute of type `xs:NMTOKENS` whose string value is `"red green blue"`, and whose typed value is therefore `("red", "green", "blue")`, then `fn:index-of(@a, "blue")` returns `3`. This is because the function calling mechanism atomizes the attribute node to produce a sequence of three `xs:NMTOKEN` values.

14.2.7 fn:starts-with-subsequence

Summary

Determines whether one sequence starts with another, using a supplied callback function to compare items.

Signature

`fn:starts-with-subsequence`(
`$input`	`as` `item()*`,
`$subsequence`	`as` `item()*`,
`$compare`	`as` `(function(item(), item()) as xs:boolean)?`	`:=` `fn:deep-equal#2`
) `as` `xs:boolean`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and implicit timezone.

The three-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function returns true if $input starts with $subsequence, when items are compared using the supplied (or default) $compare function.

More formally, the function returns the value of the expression:

count($input) ge count($subsequence) and
every(for-each-pair($input, $subsequence, $compare))

Notes

There is no requirement that the $compare function should have the traditional qualities of equality comparison. The result is well-defined, for example, even if $compare is not transitive or not symmetric.

Examples

Expression:	`starts-with-subsequence((), ())`
Result:	true()
Expression:	`starts-with-subsequence(1 to 10, 1 to 5)`
Result:	true()
Expression:	`starts-with-subsequence(1 to 10, ())`
Result:	true()
Expression:	`starts-with-subsequence(1 to 10, 1 to 10)`
Result:	true()
Expression:	`starts-with-subsequence(1 to 10, 1)`
Result:	true()
Expression:	starts-with-subsequence( 1 to 10, 101 to 105, function($x, $y) { $x mod 100 = $y mod 100 } )
Result:	true()
Expression:	starts-with-subsequence( ("A", "B", "C"), ("a", "b"), function($x, $y) { compare( $x, $y, "http://www.w3.org/2005/xpath-functions/collation/html-ascii-case-insensitive" ) eq 0 } )
Result:	true()
Expression:	let $p := parse-xml("<doc><chap><p/><p/></chap></doc>")//p[2] return starts-with-subsequence( $p/ancestor::[1], $p/parent::, op("is") )
Result:	true()
Expression:	`starts-with-subsequence(10 to 20, 1 to 5, op("gt"))`
Result:	true()
Expression:	starts-with-subsequence( ("Alpha", "Beta", "Gamma"), ("A", "B"), starts-with#2 )
Result:	true()
Expression:	starts-with-subsequence( ("Alpha", "Beta", "Gamma", "Delta"), 1 to 3, function($x, $y) { ends-with($x, 'a' ) } )
Result:	true() (True because the first three items in the input sequence end with `"a"`.)

History

New in 4.0. Accepted 2022-11-01

14.2.8 fn:ends-with-subsequence

Summary

Determines whether one sequence ends with another, using a supplied callback function to compare items.

Signature

`fn:ends-with-subsequence`(
`$input`	`as` `item()*`,
`$subsequence`	`as` `item()*`,
`$compare`	`as` `(function(item(), item()) as xs:boolean)?`	`:=` `fn:deep-equal#2`
) `as` `xs:boolean`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and implicit timezone.

The three-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function returns true if $input ends with $subsequence, when items are compared using the supplied (or default) $compare function.

More formally, the function returns the value of the expression:

starts-with-subsequence(reverse($input), reverse($subsequence), $compare)

Notes

Examples

Expression:	`ends-with-subsequence((), ())`
Result:	true()
Expression:	`ends-with-subsequence(1 to 10, 5 to 10)`
Result:	true()
Expression:	`ends-with-subsequence(1 to 10, ())`
Result:	true()
Expression:	`ends-with-subsequence(1 to 10, 1 to 10)`
Result:	true()
Expression:	`ends-with-subsequence(1 to 10, 10)`
Result:	true()
Expression:	ends-with-subsequence( 1 to 10, 108 to 110, function($x, $y) { $x mod 100 = $y mod 100 } )
Result:	true()
Expression:	ends-with-subsequence( ("A", "B", "C"), ("b", "c"), function($x, $y) { compare( $x, $y, "http://www.w3.org/2005/xpath-functions/collation/html-ascii-case-insensitive" ) eq 0 } )
Result:	true()
Expression:	let $p := parse-xml("<doc><chap><p/><p/></chap></doc>")//p[2] return ends-with-subsequence( $p/ancestor::node()[last()], $p/root(), op("is") )
Result:	true()
Expression:	`ends-with-subsequence(10 to 20, 1 to 5, op("gt"))`
Result:	true()
Expression:	ends-with-subsequence( ("Alpha", "Beta", "Gamma"), ("B", "G"), starts-with#2 )
Result:	true()
Expression:	ends-with-subsequence( ("Alpha", "Beta", "Gamma", "Delta"), 1 to 2, function($x, $y) { string-length($x) eq 5 } )
Result:	true() (True because the last two items in the input sequence have a string length of 5.)

History

New in 4.0. Accepted 2022-11-01

14.2.9 fn:contains-subsequence

Summary

Determines whether one sequence contains another as a contiguous subsequence, using a supplied callback function to compare items.

Signature

`fn:contains-subsequence`(
`$input`	`as` `item()*`,
`$subsequence`	`as` `item()*`,
`$compare`	`as` `(function(item(), item()) as xs:boolean)?`	`:=` `fn:deep-equal#2`
) `as` `xs:boolean`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and implicit timezone.

The three-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function returns true if $input contains a consecutive subsequence matching $subsequence, when items are compared using the supplied (or default) $compare function.

More formally, the function returns the value of the expression:

some $i in 0 to count($input) - count($subsequence) satisfies (
  every $j in 1 to count($subsequence)
  satisfies $compare($input[$i + $j], $subsequence[$j])
)

Notes

Examples

Expression:	`contains-subsequence((), ())`
Result:	true()
Expression:	`contains-subsequence(1 to 10, 3 to 6)`
Result:	true()
Expression:	`contains-subsequence(1 to 10, (2, 4, 6))`
Result:	false()
Expression:	`contains-subsequence(1 to 10, ())`
Result:	true()
Expression:	`contains-subsequence(1 to 10, 1 to 10)`
Result:	true()
Expression:	`contains-subsequence(1 to 10, 5)`
Result:	true()
Expression:	contains-subsequence( 1 to 10, 103 to 105, function($x, $y) { $x mod 100 = $y mod 100 } )
Result:	true()
Expression:	contains-subsequence( ("A", "B", "C", "D"), ("b", "c"), function($x, $y) { compare( $x, $y, "http://www.w3.org/2005/xpath-functions/collation/html-ascii-case-insensitive" ) eq 0 } )
Result:	true()
Expression:	let $chap := parse-xml("<doc><chap><h1/><p/><p/><footnote/></chap></doc>")//chap return contains-subsequence( $chap ! child::*, $chap ! child::p, op("is") )
Result:	true() (True because the `p` children of the `chap` element form a contiguous subsequence.)
Expression:	`contains-subsequence(10 to 20, (5, 3, 1), op("gt"))`
Result:	true()
Expression:	contains-subsequence( ("Alpha", "Beta", "Gamma", "Delta"), ("B", "G"), starts-with#2 )
Result:	true()
Expression:	contains-subsequence( ("Zero", "Alpha", "Beta", "Gamma", "Delta", "Epsilon"), 1 to 4, function($x, $y) { ends-with($x, 'a') } )
Result:	true() (True because there is a run of 4 consecutive items ending in `"a"`.)

History

New in 4.0. Accepted 2022-11-01

14.3 Functions that test the cardinality of sequences

The following functions test the cardinality of their sequence arguments.

Function	Meaning
`fn:zero-or-one`	Returns `input` if it contains zero or one items. Otherwise, raises an error.
`fn:one-or-more`	Returns `$input` if it contains one or more items. Otherwise, raises an error.
`fn:exactly-one`	Returns `$input` if it contains exactly one item. Otherwise, raises an error.

The functions fn:zero-or-one, fn:one-or-more, and fn:exactly-one defined in this section, check that the cardinality of a sequence is in the expected range. They are particularly useful with regard to static typing. For example, the function call fn:remove($seq, fn:index-of($seq2, 'abc')) requires the result of the call on fn:index-of to be a singleton integer, but the static type system cannot infer this; writing the expression as fn:remove($seq, fn:exactly-one(fn:index-of($seq2, 'abc'))) will provide a suitable static type at query analysis time, and ensures that the length of the sequence is correct with a dynamic check at query execution time.

The type signatures for these functions deliberately declare the argument type as item()*, permitting a sequence of any length. A more restrictive signature would defeat the purpose of the function, which is to defer cardinality checking until query execution time.

14.3.1 fn:zero-or-one

Summary

Returns input if it contains zero or one items. Otherwise, raises an error.

Signature

`fn:zero-or-one`(
`$input`	`as` `item()*`
) `as` `item()?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Except in error cases, the function returns $input unchanged.

Error Conditions

A dynamic error is raised [err:FORG0003] if $input contains more than one item.

14.3.2 fn:one-or-more

Summary

Returns $input if it contains one or more items. Otherwise, raises an error.

Signature

`fn:one-or-more`(
`$input`	`as` `item()*`
) `as` `item()+`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Except in error cases, the function returns $input unchanged.

Error Conditions

A dynamic error is raised [err:FORG0004] if $input is an empty sequence.

14.3.3 fn:exactly-one

Summary

Returns $input if it contains exactly one item. Otherwise, raises an error.

Signature

`fn:exactly-one`(
`$input`	`as` `item()*`
) `as` `item()`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Except in error cases, the function returns $input unchanged.

Error Conditions

A dynamic error is raised [err:FORG0005] if $input is an empty sequence or a sequence containing more than one item.

14.4 Aggregate functions

Aggregate functions take a sequence as argument and return a single value computed from values in the sequence. Except for fn:count, the sequence must consist of values of a single type or one if its subtypes, or they must be numeric. xs:untypedAtomic values are permitted in the input sequence and handled by special conversion rules. The type of the items in the sequence must also support certain operations.

Function	Meaning
`fn:count`	Returns the number of items in a sequence.
`fn:avg`	Returns the average of the values in the input sequence `$values`, that is, the sum of the values divided by the number of values.
`fn:max`	Returns a value that is equal to the highest value appearing in the input sequence.
`fn:min`	Returns a value that is equal to the lowest value appearing in the input sequence.
`fn:sum`	Returns a value obtained by adding together the values in `$values`.
`fn:all-equal`	Returns `true` if all items in a supplied sequence (after atomization) are equal.
`fn:all-different`	Returns `true` if no two items in a supplied sequence are equal.

14.4.1 fn:count

Summary

Returns the number of items in a sequence.

Signature

`fn:count`(
`$input`	`as` `item()*`
) `as` `xs:integer`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the number of items in $input.

Notes

returns 0.if $input is the empty sequence.

Examples

Variables
let $tree := <doc><chap><p/><p/><p/></chap></doc>
let $seq2 := (98.5, 98.3, 98.9)
let $seq3 := ()

Expression	Result
`count($tree//chap/p)`	3
`count($seq3)`	0
`count($seq2)`	3
`count($seq2[. > 100])`	0
`count([])`	1
`count([1,2,3])`	1

14.4.2 fn:avg

Summary

Returns the average of the values in the input sequence $values, that is, the sum of the values divided by the number of values.

Signature

`fn:avg`(
`$values`	`as` `xs:anyAtomicType*`
) `as` `xs:anyAtomicType?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $values is the empty sequence, the empty sequence is returned.

If $values contains values of type xs:untypedAtomic they are cast to xs:double.

Duration values must either all be xs:yearMonthDuration values or must all be xs:dayTimeDuration values. For numeric values, the numeric promotion rules defined in 4.2 Arithmetic operators on numeric values are used to promote all values to a single common type. After these operations, $values must satisfy the following condition:

There must be a type T such that:

every item in $values is an instance of T.
T is one of xs:double, xs:float, xs:decimal, xs:yearMonthDuration, or xs:dayTimeDuration.

The function returns the average of the values as sum($values) div count($values); but the implementation may use an otherwise equivalent algorithm that avoids arithmetic overflow.

Error Conditions

A type error is raised [err:FORG0006] if the input sequence contains items of incompatible types, as described above.

Examples

Variables
let $d1 := xs:yearMonthDuration("P20Y")
let $d2 := xs:yearMonthDuration("P10M")
let $seq3 := (3, 4, 5)

Expression	Result
`avg($seq3)`	4.0 (The result is of type `xs:decimal`.)
`avg(($d1, $d2))`	xs:yearMonthDuration("P10Y5M")
`avg(())`	()
`avg((xs:float('INF'), xs:float('-INF')))`	xs:float('NaN')
`avg(($seq3, xs:float('NaN')))`	xs:float('NaN')
`fn:avg(($d1, $seq3))` raises a type error [err:FORG0006].

14.4.3 fn:max

Summary

Returns a value that is equal to the highest value appearing in the input sequence.

Signature

`fn:max`(
`$values`	`as` `xs:anyAtomicType*`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:anyAtomicType?`

Properties

The one-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and implicit timezone.

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI, and implicit timezone.

Rules

Any item in $values that is an instance of xs:untypedAtomic is first cast to xs:double. The resulting sequence is referred to as the converted sequence.

All pairs of values in the converted sequence must be mutually comparable. Two values are mutually comparable if one or more of the following conditions applies:

Both values are instances of xs:string or xs:anyURI.
Both values are instances of xs:numeric.
Both values are instances of xs:hexBinary or xs:base64Binary.
Both values are instances of xs:date.
Both values are instances of xs:dateTime.
Both values are instances of xs:time.
Both values are instances of xs:dayTimeDuration.
Both values are instances of xs:yearMonthDuration.
Both values are instances of xs:boolean.

If the converted sequence contains a single value then it must be comparable to itself under the above rules. (So the input cannot be, for example, a singleton xs:QName.)

If the converted sequence is empty, the function returns the empty sequence.

If the converted sequence contains the value NaN, the value NaN is returned (as an xs:float or xs:double as appropriate).

Two items $v1 and $v2 from the converted sequence are compared as follows:

If both values are instances of xs:string or xs:anyURI, they are compared using fn:compare($v1, $v2, $collation), where $collation is determined by the rules in 5.3.5 Choosing a collation.

Note:

In other cases, $collation is ignored.
If both values are instances of xs:numeric, they are compared using fn:compare($v1, $v2).
In all other cases, the values are compared using the lt and eq operators appropriate to their type.

The result of the function is a value from the converted sequence that is greater than or equal to every other value under the above rules. If there is more than one such value, then it is ·implementation-dependent· which of them is returned.

Error Conditions

A type error is raised [err:FORG0006] if the input sequence contains items of incompatible types, as described above.

Notes

If there are two or items that are “equal highest”, the specific item whose value is returned is ·implementation-dependent·. This can arise for example if two different strings compare equal under the selected collation, or if two different xs:dateTime values compare equal despite being in different timezones.

If the converted sequence contains exactly one value then that value is returned.

The default type when the fn:max function is applied to xs:untypedAtomic values is xs:double. This differs from the default type for operators such as lt, and for sorting in XQuery and XSLT, which is xs:string.

In version 4.0, if $values is a sequence of xs:decimal values (including the case where it is a sequence of xs:integer values), then the result will be one of these xs:decimal or xs:integer values. In earlier versions it would be the result of converting this xs:decimal to xs:double.

Examples

Expression	Result
`max((3,2,1))`	3
`max([3,2,1])`	3 (Arrays are atomized).
`max((xs:integer(5), xs:float(5), xs:double(0)))`	5 (The result may be either the `xs:integer` or the `xs:float`, since they are equal.)
`max((xs:float(0.0E0), xs:float(-0.0E0)))`	xs:float(0.0e0) (The result may be either positive or negative zero, since they are equal.)
`max((current-date(), xs:date("2100-01-01")))`	xs:date("2100-01-01") (Assuming that the current date is during the 21st century.)
`max(("a", "b", "c"))`	"c" (Assuming a typical default collation.)
`max((3,4,"Zero"))` raises a type error [err:FORG0006].

14.4.4 fn:min

Summary

Returns a value that is equal to the lowest value appearing in the input sequence.

Signature

`fn:min`(
`$values`	`as` `xs:anyAtomicType*`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:anyAtomicType?`

Properties

The one-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and implicit timezone.

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI, and implicit timezone.

Rules

Any item in $values that is an instance of xs:untypedAtomic is first cast to xs:double. The resulting sequence is referred to as the converted sequence.

All pairs of values in the converted sequence must be mutually comparable. Two values are mutually comparable if one or more of the following conditions applies:

Both values are instances of xs:string or xs:anyURI.
Both values are instances of xs:numeric.
Both values are instances of xs:hexBinary or xs:base64Binary.
Both values are instances of xs:date.
Both values are instances of xs:dateTime.
Both values are instances of xs:time.
Both values are instances of xs:dayTimeDuration.
Both values are instances of xs:yearMonthDuration.
Both values are instances of xs:boolean.

If the converted sequence contains a single value then it must be comparable to itself under the above rules. (So the input cannot be, for example, a singleton xs:QName.)

If the converted sequence is empty, the function returns the empty sequence.

If the converted sequence contains the value NaN, the value NaN is returned (as an xs:float or xs:double as appropriate).

Two items $v1 and $v2 from the converted sequence are compared as follows:

If both values are instances of xs:string or xs:anyURI, they are compared using fn:compare($v1, $v2, $collation), where $collation is determined by the rules in 5.3.5 Choosing a collation.

Note:

In other cases, $collation is ignored.
If both values are instances of xs:numeric, they are compared using fn:compare($v1, $v2).
In all other cases, the values are compared using the lt and eq operators appropriate to their type.

The result of the function is a value from the converted sequence that is less than or equal to every other value under the above rules. If there is more than one such value, then it is ·implementation-dependent· which of them is returned.

Error Conditions

A type error is raised [err:FORG0006] if the input sequence contains items of incompatible types, as described above.

Notes

If there are two or items that are “equal lowest”, the specific item whose value is returned is ·implementation-dependent·. This can arise for example if two different strings compare equal under the selected collation, or if two different xs:dateTime values compare equal despite being in different timezones.

If the converted sequence contains exactly one value then that value is returned.

The default type when the fn:min function is applied to xs:untypedAtomic values is xs:double. This differs from the default type for operators such as lt, and for sorting in XQuery and XSLT, which is xs:string.

Examples

Expression	Result
`min((3,4,5))`	3
`min([3,4,5])`	3 (Arrays are atomized).
`min((xs:integer(5), xs:float(5), xs:double(10)))`	5 (The result may be either the `xs:integer` or the `xs:float`, since they are equal.)
`min((xs:float(0.0E0), xs:float(-0.0E0)))`	xs:float(0.0e0) (The result may be either positive or negative zero, since they are equal.)
`min((current-date(), xs:date("1900-01-01")))`	xs:date("1900-01-01") (Assuming that the current date is set to a reasonable value.)
`min(("a", "b", "c"))`	"a" (Assuming a typical default collation.)
`min((3,4,"Zero"))` raises a type error [err:FORG0006].

14.4.5 fn:sum

Summary

Returns a value obtained by adding together the values in $values.

Signature

`fn:sum`(
`$values`	`as` `xs:anyAtomicType*`,
`$zero`	`as` `xs:anyAtomicType?`	`:=` `0`
) `as` `xs:anyAtomicType?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Any values of type xs:untypedAtomic in $values are cast to xs:double. The items in the resulting sequence may be reordered in an arbitrary order. The resulting sequence is referred to below as the converted sequence.

If the converted sequence is empty, then the function returns the value of the argument $zero, which defaults to the xs:integer value 0.

If the converted sequence contains the value NaN, NaN is returned.

All items in $values must be numeric or derived from a single base type. In addition, the type must support addition. Duration values must either all be xs:yearMonthDuration values or must all be xs:dayTimeDuration values. For numeric values, the numeric promotion rules defined in 4.2 Arithmetic operators on numeric values are used to promote all values to a single common type. The sum of a sequence of integers will therefore be an integer, while the sum of a numeric sequence that includes at least one xs:double will be an xs:double.

The result of the function is the value of the expression:

if (count($c) eq 0) then $zero
else if (count($c) eq 1) then $c[1]
else $c[1] + sum(subsequence($c, 2))

where $c is the converted sequence.

The result of the function when a single argument is supplied is the result of the expression: fn:sum($arg, 0).

Error Conditions

A type error is raised [err:FORG0006] if the input sequence contains items of incompatible types, as described above.

Notes

The second argument allows an appropriate value to be defined to represent the sum of an empty sequence. For example, when summing a sequence of durations it would be appropriate to return a zero-length duration of the appropriate type. This argument is necessary because a system that does dynamic typing cannot distinguish “an empty sequence of integers", for example, from “an empty sequence of durations”.

The explicit or implicit value of the $zero argument is used only when the input sequence is empty, not when a non-empty sequence sums to zero. For example, sum((-1, +1), xs:double('NaN')) returns the xs:integer value 0, not NaN.

If the converted sequence contains exactly one value then that value is returned.

Examples

Variables
let $d1 := xs:yearMonthDuration("P20Y")
let $d2 := xs:yearMonthDuration("P10M")
let $seq1 := ($d1, $d2)
let $seq3 := (3, 4, 5)

Expression:	`sum(($d1, $d2))`
Result:	xs:yearMonthDuration("P20Y10M")
Expression:	sum( $seq1[. lt xs:yearMonthDuration('P3M')], xs:yearMonthDuration('P0M') )
Result:	xs:yearMonthDuration("P0M")
Expression:	`sum($seq3)`
Result:	12
Expression:	`sum(())`
Result:	0
Expression:	`sum((),())`
Result:	()
Expression:	`sum((1 to 100)[. lt 0], 0)`
Result:	0
Expression:	`sum(($d1, $d2), "ein Augenblick")`
Result:	xs:yearMonthDuration("P20Y10M") (There is no requirement that the `$zero` value should be the same type as the items in `$value`, or even that it should belong to a type that supports addition.)
Expression:	`sum([1, 2, 3])`
Result:	6 (Atomizing an array returns the sequence obtained by atomizing its members.)
Expression:	`sum([[1, 2], [3, 4]])`
Result:	10 (Atomizing an array returns the sequence obtained by atomizing its members.)
`fn:sum(($d1, 9E1))` raises a type error [err:FORG0006].

14.4.6 fn:all-equal

Summary

Returns true if all items in a supplied sequence (after atomization) are equal.

Signature

`fn:all-equal`(
`$values`	`as` `xs:anyAtomicType*`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

Rules

Omitting the second argument, $collation, is equivalent to supplying fn:default-collation(). For more information on collations see 5.3.5 Choosing a collation.

The result of the function fn:all-equal($values, $collation) is true if and only if the result of fn:count(fn:distinct-values($values, $collation)) le 1 is true (that is, if the sequence is empty, or if all the items in the sequence are equal under the rules of the fn:distinct-values function).

Examples

Expression:	`all-equal((1,2,3))`
Result:	false()
Expression:	`all-equal((1, 1.0, 1.0e0))`
Result:	true()
Expression:	`all-equal("one")`
Result:	true()
Expression:	`all-equal(())`
Result:	true()
Expression:	all-equal( ("ABC", "abc"), "http://www.w3.org/2005/xpath-functions/collation/html-ascii-case-insensitive" )
Result:	true()
The expression `fn:all-equal(//p/@class)` returns `true` if all `p` elements have the same value for `@class`.
The expression `fn:all-equal(*!fn:node-name())` returns `true` if all element children of the context node have the same name.

History

Originally proposed for 4.0 under the name fn:uniform. Accepted 2022-09-20 with a change of name.

14.4.7 fn:all-different

Summary

Returns true if no two items in a supplied sequence are equal.

Signature

`fn:all-different`(
`$values`	`as` `xs:anyAtomicType*`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

Rules

Omitting the second argument, $collation, is equivalent to supplying fn:default-collation(). For more information on collations see 5.3.5 Choosing a collation.

The result of the function fn:all-different($values, $collation) is true if and only if the result of fn:count(fn:distinct-values($values, $collation)) eq fn:count($values) is true (that is, if the sequence is empty, or if all the items in the sequence are distinct under the rules of the fn:distinct-values function).

Examples

Expression:	`all-different((1,2,3))`
Result:	true()
Expression:	`all-different((1, 1.0, 1.0e0))`
Result:	false()
Expression:	`all-different("one")`
Result:	true()
Expression:	`all-different(())`
Result:	true()
Expression:	all-different( ("ABC", "abc"), "http://www.w3.org/2005/xpath-functions/collation/html-ascii-case-insensitive" )
Result:	false()
The expression `fn:all-different(//employee/@ssn)` is `true` if no two employees have the same value for their `@ssn` attribute.
The expression `fn:all-different(*!fn:node-name())` returns `true` if all element children of the context node have distinct names.

History

Originally proposed for 4.0 under the name fn:unique. Accepted 2022-09-20 with a change of name and with clarifications to the description.

14.5 Functions on node identifiers

This section defines a number of functions used to find elements by ID or IDREF value, or to generate IDs.

Function	Meaning
`fn:id`	Returns the sequence of element nodes that have an `ID` value matching the value of one or more of the `IDREF` values supplied in `$values`.
`fn:element-with-id`	Returns the sequence of element nodes that have an `ID` value matching the value of one or more of the `IDREF` values supplied in `$values`.
`fn:idref`	Returns the sequence of element or attribute nodes with an `IDREF` value matching the value of one or more of the `ID` values supplied in `$values`.
`fn:generate-id`	This function returns a string that uniquely identifies a given node.

14.5.1 fn:id

Summary

Returns the sequence of element nodes that have an ID value matching the value of one or more of the IDREF values supplied in $values.

Signature

`fn:id`(
`$values`	`as` `xs:string*`,
`$node`	`as` `node()`	`:=` `.`
) `as` `element()*`

Properties

The one-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The two-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns a sequence, in document order with duplicates eliminated, containing every element node E that satisfies all the following conditions:

E is in the target document. The target document is the document containing $node, or the document containing the context value (.) if the second argument is omitted. The behavior of the function if $node is omitted is exactly the same as if the context value had been passed as $node.
E has an ID value equal to one of the candidate IDREF values, where:
- An element has an ID value equal to V if either or both of the following conditions are true:
  - The is-id property (See Section 4.5 is-id Accessor^DM40.) of the element node is true, and the typed value of the element node is equal to V under the rules of the eq operator using the Unicode codepoint collation (http://www.w3.org/2005/xpath-functions/collation/codepoint).
  - The element has an attribute node whose is-id property (See Section 4.5 is-id Accessor^DM40.) is true and whose typed value is equal to V under the rules of the eq operator using the Unicode code point collation (http://www.w3.org/2005/xpath-functions/collation/codepoint).
- Each xs:string in $values is parsed as if it were of type IDREFS, that is, each xs:string in $values is treated as a whitespace-separated sequence of tokens, each acting as an IDREF. These tokens are then included in the list of candidate IDREFs. If any of the tokens is not a lexically valid IDREF (that is, if it is not lexically an xs:NCName), it is ignored. Formally, the candidate IDREF values are the strings in the sequence given by the expression:
```
for $s in $values return 
    tokenize(normalize-space($s), ' ')[. castable as xs:IDREF]
```
If several elements have the same ID value, then E is the one that is first in document order.

Error Conditions

A dynamic error is raised [err:FODC0001] if $node, or the context value if the second argument is absent, is a node in a tree whose root is not a document node.

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Notes

The effect of this function is anomalous in respect of element nodes with the is-id property. For legacy reasons, this function returns the element that has the is-id property, whereas it would be more appropriate to return its parent, that being the element that is uniquely identified by the ID. A new function fn:element-with-id has been introduced with the desired behavior.

If the data model is constructed from an Infoset, an attribute will have the is-id property if the corresponding attribute in the Infoset had an attribute type of ID: typically this means the attribute was declared as an ID in a DTD.

If the data model is constructed from a PSVI, an element or attribute will have the is-id property if its typed value is a single atomic value of type xs:ID or a type derived by restriction from xs:ID.

No error is raised in respect of a candidate IDREF value that does not match the ID of any element in the document. If no candidate IDREF value matches the ID value of any element, the function returns the empty sequence.

It is not necessary that the supplied argument should have type xs:IDREF or xs:IDREFS, or that it should be derived from a node with the is-idrefs property.

An element may have more than one ID value. This can occur with synthetic data models or with data models constructed from a PSVI where the element and one of its attributes are both typed as xs:ID.

If the source document is well-formed but not valid, it is possible for two or more elements to have the same ID value. In this situation, the function will select the first such element.

It is also possible in a well-formed but invalid document to have an element or attribute that has the is-id property but whose value does not conform to the lexical rules for the xs:ID type. Such a node will never be selected by this function.

Examples

Variables

let $emp := 
        validate lax{    
          document{
            <employee xml:id="ID21256"
                      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
                      xmlns:xs="http://www.w3.org/2001/XMLSchema">
               <empnr xsi:type="xs:ID">E21256</empnr>
               <first>John</first>
               <last>Brown</last>
            </employee>
          }
        }

Expression	Result
`$emp/id('ID21256')/name()`	"employee" (The `xml:id` attribute has the `is-id` property, so the employee element is selected.)
`$emp/id('E21256')/name()`	"empnr" (Assuming the `empnr` element is given the type `xs:ID` as a result of schema validation, the element will have the `is-id` property and is therefore selected. Note the difference from the behavior of `fn:element-with-id`.)

14.5.2 fn:element-with-id

Summary

Returns the sequence of element nodes that have an ID value matching the value of one or more of the IDREF values supplied in $values.

Signature

`fn:element-with-id`(
`$values`	`as` `xs:string*`,
`$node`	`as` `node()`	`:=` `.`
) `as` `element()*`

Properties

The one-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The two-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Note:

The effect of this function is identical to fn:id in respect of elements that have an attribute with the is-id property. However, it behaves differently in respect of element nodes with the is-id property. Whereas the fn:id function, for legacy reasons, returns the element that has the is-id property, this function returns the element identified by the ID, which is the parent of the element having the is-id property.

The function returns a sequence, in document order with duplicates eliminated, containing every element node E that satisfies all the following conditions:

E is in the target document. The target document is the document containing $node, or the document containing the context value (.) if the second argument is omitted. The behavior of the function if $node is omitted is exactly the same as if the context value had been passed as $node.
E has an ID value equal to one of the candidate IDREF values, where:
- An element has an ID value equal to V if either or both of the following conditions are true:
  - The element has an child element node whose is-id property (See Section 4.5 is-id Accessor^DM40.) is true and whose typed value is equal to V under the rules of the eq operator using the Unicode code point collation (http://www.w3.org/2005/xpath-functions/collation/codepoint).
  - The element has an attribute node whose is-id property (See Section 4.5 is-id Accessor^DM40.) is true and whose typed value is equal to V under the rules of the eq operator using the Unicode code point collation (http://www.w3.org/2005/xpath-functions/collation/codepoint).
- Each xs:string in $values is parsed as if it were of type IDREFS, that is, each xs:string in $values is treated as a whitespace-separated sequence of tokens, each acting as an IDREF. These tokens are then included in the list of candidate IDREFs. If any of the tokens is not a lexically valid IDREF (that is, if it is not lexically an xs:NCName), it is ignored. Formally, the candidate IDREF values are the strings in the sequence given by the expression:
```
for $s in $arg return 
   tokenize(normalize-space($s), ' ')[. castable as xs:IDREF]
```
If several elements have the same ID value, then E is the one that is first in document order.

Error Conditions

A dynamic error is raised [err:FODC0001] if $node, or the context value if the second argument is omitted, is a node in a tree whose root is not a document node.

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Notes

This function is equivalent to the fn:id function except when dealing with ID-valued element nodes. Whereas the fn:id function selects the element containing the identifier, this function selects its parent.

It is not necessary that the supplied argument should have type xs:IDREF or xs:IDREFS, or that it should be derived from a node with the is-idrefs property.

If the source document is well-formed but not valid, it is possible for two or more elements to have the same ID value. In this situation, the function will select the first such element.

Examples

Variables

let $emp := 
         validate lax{    
          document{
            <employee xml:id="ID21256"
                      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
                      xmlns:xs="http://www.w3.org/2001/XMLSchema">
               <empnr xsi:type="xs:ID">E21256</empnr>
               <first>John</first>
               <last>Brown</last>
            </employee>
          }
        }

Expression	Result
`$emp/element-with-id('ID21256')/name()`	"employee" (The `xml:id` attribute has the `is-id` property, so the employee element is selected.)
`$emp/element-with-id('E21256')/name()`	"employee" (Assuming the `empnr` element is given the type `xs:ID` as a result of schema validation, the element will have the `is-id` property and is therefore its parent is selected. Note the difference from the behavior of `fn:id`.)

14.5.3 fn:idref

Summary

Returns the sequence of element or attribute nodes with an IDREF value matching the value of one or more of the ID values supplied in $values.

Signature

`fn:idref`(
`$values`	`as` `xs:string*`,
`$node`	`as` `node()`	`:=` `.`
) `as` `node()*`

Properties

The one-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The two-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns a sequence, in document order with duplicates eliminated, containing every element or attribute node $N that satisfies all the following conditions:

$N is in the target document. The target document is the document containing $node, or the document containing the context value (.) if the second argument is omitted. The behavior of the function if $node is omitted is exactly the same as if the context value had been passed as $node.
$N has an IDREF value equal to one of the candidate ID values, where:
- A node $N has an IDREF value equal to V if both of the following conditions are true:
  - The is-idrefs property (see Section 4.6 is-idrefs Accessor^DM40) of $N is true.
  - The sequence
```
tokenize(normalize-space(string($N)), ' ')
```
    contains a string that is equal to V under the rules of the eq operator using the Unicode code point collation (http://www.w3.org/2005/xpath-functions/collation/codepoint).
- Each xs:string in $values is parsed as if it were of lexically of type xs:ID. These xs:strings are then included in the list of candidate xs:IDs. If any of the strings in $values is not a lexically valid xs:ID (that is, if it is not lexically an xs:NCName), it is ignored. More formally, the candidate ID values are the strings in the sequence:
```
$values[. castable as xs:NCName]
```

Error Conditions

A dynamic error is raised [err:FODC0001] if $node, or the context value if the second argument is omitted, is a node in a tree whose root is not a document node.

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Notes

An element or attribute typically acquires the is-idrefs property by being validated against the schema type xs:IDREF or xs:IDREFS, or (for attributes only) by being described as of type IDREF or IDREFS in a DTD.

Because the function is sensitive to the way in which the data model is constructed, calls on this function are not always interoperable.

No error is raised in respect of a candidate ID value that does not match the IDREF value of any element or attribute in the document. If no candidate ID value matches the IDREF value of any element or attribute, the function returns the empty sequence.

It is possible for two or more nodes to have an IDREF value that matches a given candidate ID value. In this situation, the function will return all such nodes. However, each matching node will be returned at most once, regardless how many candidate ID values it matches.

It is possible in a well-formed but invalid document to have a node whose is-idrefs property is true but that does not conform to the lexical rules for the xs:IDREF type. The effect of the above rules is that ill-formed candidate ID values and ill-formed IDREF values are ignored.

If the data model is constructed from a PSVI, the typed value of a node that has the is-idrefs property will contain at least one atomic value of type xs:IDREF (or a type derived by restriction from xs:IDREF). It may also contain atomic values of other types. These atomic values are treated as candidate ID values if two conditions are met: their lexical form must be valid as an xs:NCName, and there must be at least one instance of xs:IDREF in the typed value of the node. If these conditions are not satisfied, such values are ignored.

Examples

Variables

let $emp := 
      validate lax {  
        document {    
          <employees xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
                     xmlns:xs="http://www.w3.org/2001/XMLSchema">  
            <employee xml:id="ID21256">
               <empnr xsi:type="xs:ID">E21256</empnr>
               <first>Anil</first>
               <last>Singh</last>
               <deputy xsi:type="xs:IDREF">E30561</deputy>
            </employee>
            <employee xml:id="ID30561">
               <empnr xsi:type="xs:ID">E30561</empnr>
               <first>John</first>
               <last>Brown</last>
               <manager xsi:type="xs:IDREF">ID21256</manager>
            </employee>
          </employees>
        }
      }

Expression:	$emp/( element-with-id('ID21256')/@xml:id => idref() )/ancestor::employee/last => string()
Result:	"Brown" (Assuming that `manager` has the is-idref property, the call on `fn:idref` selects the `manager` element. If, instead, the `manager` had a `ref` attribute with the is-idref property, the call on `fn:idref` would select the attribute node.)
Expression:	$emp/( element-with-id('E30561')/empnr => idref() )/ancestor::employee/last => string()
Result:	"Singh" (Assuming that `employee/deputy` has the is-idref property, the call on `fn:idref` selects the `deputy` element.)

14.5.4 fn:generate-id

Summary

This function returns a string that uniquely identifies a given node.

Signature

`fn:generate-id`(
`$node`	`as` `node()?`	`:=` `.`
) `as` `xs:string`

Properties

The zero-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

The one-argument form of this function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If the argument is the empty sequence, the result is the zero-length string.

In other cases, the function returns a string that uniquely identifies a given node. More formally, it is guaranteed that within a single ·execution scope·, fn:codepoint-equal(fn:generate-id($N), fn:generate-id($M)) returns true if and only if ($M is $N) returns true.

The returned identifier must consist of ASCII alphanumeric characters and must start with an alphabetic character. Thus, the string is syntactically an XML name.

Error Conditions

The following errors may be raised when $node is omitted:

If the context value is absent^DM40, type error [err:XPDY0002]^XP
If the context value is not a single node, type error [err:XPTY0004]^XP.

Notes

An implementation is free to generate an identifier in any convenient way provided that it always generates the same identifier for the same node and that different identifiers are always generated from different nodes. An implementation is under no obligation to generate the same identifiers each time a document is transformed or queried.

There is no guarantee that a generated unique identifier will be distinct from any unique IDs specified in the source document.

There is no inverse to this function; it is not directly possible to find the node with a given generated ID. Of course, it is possible to search a given sequence of nodes using an expression such as $nodes[generate-id()=$id].

It is advisable, but not required, for implementations to generate IDs that are distinct even when compared using a case-blind collation.

Examples

The primary use case for this function is to generate hyperlinks. For example, when generating HTML, an anchor for a given section `$sect` can be generated by writing (in either XSLT or XQuery):
`<a name="{fn:generate-id($sect)}"/>`
and a link to that section can then be produced with code such as:
`see <a href="#{fn:generate-id($sect)}">here</a>`
Note that anchors generated in this way will not necessarily be the same each time a document is republished.
Since the keys in a map must be atomic values, it is possible to use generated IDs as surrogates for nodes when constructing a map. For example, in some implementations, testing whether a node `$N` is a member of a large node-set `$S` using the expression `fn:exists($N intersect $S)` may be expensive; there may then be performance benefits in creating a map:
`let $SMap := map:merge($S!map{fn:generate-id(.) : .})`
and then testing for membership of the node-set using:
`map:contains($SMap, generate-id($N))`

14.6 Functions giving access to external information

The functions in this section provide access to resources (such as files) in the external environment.

Function	Meaning
`fn:doc`	Retrieves a document using a URI supplied as an `xs:string`, and returns the corresponding document node.
`fn:doc-available`	The function returns `true` if and only if the function call `fn:doc($href)` would return a document node.
`fn:collection`	Returns a sequence of items identified by a collection URI; or a default collection if no URI is supplied.
`fn:uri-collection`	Returns a sequence of `xs:anyURI` values representing the URIs in a URI collection.
`fn:unparsed-text`	The `fn:unparsed-text` function reads an external resource (for example, a file) and returns a string representation of the resource.
`fn:unparsed-text-lines`	The `fn:unparsed-text-lines` function reads an external resource (for example, a file) and returns its contents as a sequence of strings, one for each line of text in the string representation of the resource.
`fn:unparsed-text-available`	Because errors in evaluating the `fn:unparsed-text` function are non-recoverable, these two functions are provided to allow an application to determine whether a call with particular arguments would succeed.
`fn:environment-variable`	Returns the value of a system environment variable, if it exists.
`fn:available-environment-variables`	Returns a list of environment variable names that are suitable for passing to `fn:environment-variable`, as a (possibly empty) sequence of strings.

14.6.1 fn:doc

Summary

Retrieves a document using a URI supplied as an xs:string, and returns the corresponding document node.

Signature

`fn:doc`(
`$href`	`as` `xs:string?`
) `as` `document-node()?`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on available documents, and static base URI.

Rules

If $href is the empty sequence, the result is an empty sequence.

If $href is a relative URI reference, it is resolved relative to the value of the static base URI property from the static context. The resulting absolute URI is promoted to an xs:string.

If the available documents described in Section 2.1.2 Dynamic Context ^XP31 provides a mapping from this string to a document node, the function returns that document node.

The URI may include a fragment identifier.

By default, this function is ·deterministic·. Two calls on this function return the same document node if the same URI Reference (after resolution to an absolute URI Reference) is supplied to both calls. Thus, the following expression (if it does not raise an error) will always return true:

doc("foo.xml") is doc("foo.xml")

Note:

This equivalence applies only because the two calls on the doc function have the same dynamic context. If two calls on doc have different dynamic contexts, then the mapping from URIs to document nodes in the two contexts may differ, which means that different document nodes may be returned for the same URI. This can happen, for example, if the two calls appear in different XSLT packages with different validation options or whitespace-stripping options; one call might produce a schema-validated document, the other an untyped document.

The requirement to deliver a deterministic result has performance implications, and for this reason implementations may provide a user option to evaluate the function without a guarantee of determinism. The manner in which any such option is provided is ·implementation-defined·. If the user has not selected such an option, a call of the function must either return a deterministic result or must raise a dynamic error [err:FODC0003].

Note:

If $href is read from a source document, it is generally appropriate to resolve it relative to the base URI property of the relevant node in the source document. This can be achieved by calling the fn:resolve-uri function, and passing the resulting absolute URI as an argument to the fn:doc function.

If two calls to this function supply different absolute URI References as arguments, the same document node may be returned if the implementation can determine that the two arguments refer to the same resource.

By defining the semantics of this function in terms of a string-to-document-node mapping in the dynamic context, the specification is acknowledging that the results of this function are outside the purview of the language specification itself, and depend entirely on the run-time environment in which the expression is evaluated. This run-time environment includes not only an unpredictable collection of resources (“the web”), but configurable machinery for locating resources and turning their contents into document nodes within the XPath data model. Both the set of resources that are reachable, and the mechanisms by which those resources are parsed and validated, are ·implementation-dependent·.

One possible processing model for this function is as follows. The resource identified by the URI Reference is retrieved. If the resource cannot be retrieved, a dynamic error is raised [err:FODC0002]. The data resulting from the retrieval action is then parsed as an XML document and a tree is constructed in accordance with the [XQuery and XPath Data Model (XDM) 3.0]. If the top-level media type is known and is "text", the content is parsed in the same way as if the media type were text/xml; otherwise, it is parsed in the same way as if the media type were application/xml. If the contents cannot be parsed successfully, a dynamic error is raised [err:FODC0002]. Otherwise, the result of the function is the document node at the root of the resulting tree. This tree is then optionally validated against a schema.

Various aspects of this processing are ·implementation-defined·. Implementations may provide external configuration options that allow any aspect of the processing to be controlled by the user. In particular:

The set of URI schemes that the implementation recognizes is implementation-defined. Implementations may allow the mapping of URIs to resources to be configured by the user, using mechanisms such as catalogs or user-written URI handlers.
The handling of non-XML media types is implementation-defined. Implementations may allow instances of the data model to be constructed from non-XML resources, under user control.
It is ·implementation-defined· whether DTD validation and/or schema validation is applied to the source document.
Implementations may provide user-defined error handling options that allow processing to continue following an error in retrieving a resource, or in parsing and validating its content. When errors have been handled in this way, the function may return either an empty sequence, or a fallback document provided by the error handler.
Implementations may provide user options that relax the requirement for the function to return deterministic results.
The effect of a fragment identifier in the supplied URI is ·implementation-defined·. One possible interpretation is to treat the fragment identifier as an ID attribute value, and to return a document node having the element with the selected ID value as its only child.

Error Conditions

A dynamic error may be raised [err:FODC0005] if $href is not a valid URI reference.

A dynamic error is raised [err:FODC0002] if a relative URI reference is supplied, and the base-URI property in the static context is absent.

A dynamic error is raised [err:FODC0002] if the available documents provides no mapping for the absolutized URI.

A dynamic error is raised [err:FODC0002] if the resource cannot be retrieved or cannot be parsed successfully as XML.

A dynamic error is raised [err:FODC0003] if the implementation is not able to guarantee that the result of the function will be deterministic, and the user has not indicated that an unstable result is acceptable.

14.6.2 fn:doc-available

Summary

The function returns true if and only if the function call fn:doc($href) would return a document node.

Signature

`fn:doc-available`(
`$href`	`as` `xs:string?`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on available documents, and static base URI.

Rules

If $href is an empty sequence, this function returns false.

If a call on fn:doc($href) would return a document node, this function returns true.

In all other cases this function returns false. This includes the case where an invalid URI is supplied, and also the case where a valid relative URI reference is supplied, and cannot be resolved, for example because the static base URI is absent.

If this function returns true, then calling fn:doc($href) within the same ·execution scope· must return a document node. However, if nondeterministic processing has been selected for the fn:doc function, this guarantee is lost.

14.6.3 fn:collection

Summary

Returns a sequence of items identified by a collection URI; or a default collection if no URI is supplied.

Signature

`fn:collection`(
`$uri`	`as` `xs:string?`	`:=` `()`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on available collections, and static base URI.

Rules

This function takes an xs:string as argument and returns a sequence of items obtained by interpreting $uri as an xs:anyURI and resolving it according to the mapping specified in available collections described in Section C.2 Dynamic Context Components ^XP31.

If available collections provides a mapping from this string to a sequence of items, the function returns that sequence. If available collections maps the string to an empty sequence, then the function returns an empty sequence.

If $uri is not specified, the function returns the sequence of items in the default collection in the dynamic context. See Section C.2 Dynamic Context Components ^XP31.

If $uri is a relative xs:anyURI, it is resolved against the value of the base-URI property from the static context.

If $uri is the empty sequence, the function behaves as if it had been called without an argument. See above.

By default, this function is ·deterministic·. This means that repeated calls on the function with the same argument will return the same result. However, for performance reasons, implementations may provide a user option to evaluate the function without a guarantee of determinism. The manner in which any such option is provided is ·implementation-defined·. If the user has not selected such an option, a call to this function must either return a deterministic result or must raise a dynamic error [err:FODC0003].

There is no requirement that any nodes in the result should be in document order, nor is there a requirement that the result should contain no duplicates.

Error Conditions

A dynamic error is raised [err:FODC0002] if no URI is supplied and the value of the default collection is absent^DM40.

A dynamic error is raised [err:FODC0002] if a relative URI reference is supplied, and the base-URI property in the static context is absent.

A dynamic error is raised [err:FODC0002] if available node collections provides no mapping for the absolutized URI.

A dynamic error may be raised [err:FODC0004] if $uri is not a valid xs:anyURI.

Notes

In earlier versions of this specification, the primary use for the fn:collection function was to retrieve a collection of XML documents, perhaps held as lexical XML in operating system filestore, or perhaps held in an XML database. In this release the concept has been generalised to allow other resources to be retrieved: for example JSON documents might be returned as arrays or maps, non-XML text files might be returned as strings, and binary files might be returned as instances of xs:base64Binary.

The abstract concept of a collection might be realized in different ways by different implementations, and the ways in which URIs map to collections can be equally variable. Specifying resources using URIs is useful because URIs are dynamic, can be parameterized, and do not rely on an external environment.

14.6.4 fn:uri-collection

Summary

Returns a sequence of xs:anyURI values representing the URIs in a URI collection.

Signature

`fn:uri-collection`(
`$uri`	`as` `xs:string?`	`:=` `()`
) `as` `xs:anyURI*`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on available URI collections, and static base URI.

Rules

The zero-argument form of the function returns the URIs in the default URI collection described in Section C.2 Dynamic Context Components ^XP31.

If $uri is a relative xs:anyURI, it is resolved against the value of the base-URI property from the static context.

If $uri is the empty sequence, the function behaves as if it had been called without an argument. See above.

The single-argument form of the function returns the sequence of URIs corresponding to the supplied URI in the available URI collections described in Section C.2 Dynamic Context Components ^XP31.

There is no requirement that the URIs returned by this function should all be distinct, and no assumptions can be made about the order of URIs in the sequence, unless the implementation defines otherwise.

Error Conditions

A dynamic error is raised [err:FODC0002] if no URI is supplied (that is, if the function is called with no arguments, or with a single argument that evaluates to an empty sequence), and the value of the default resource collection is absent^DM40.

A dynamic error is raised [err:FODC0002] if a relative URI reference is supplied, and the base-URI property in the static context is absent.

A dynamic error is raised [err:FODC0002] if available resource collections provides no mapping for the absolutized URI.

A dynamic error may be raised [err:FODC0004] if $uri is not a valid xs:anyURI.

Notes

In some implementations, there might be a close relationship between collections (as retrieved by the fn:collection function), and URI collections (as retrieved by this function). For example, a collection might return XML documents, and the corresponding URI collection might return the URIs of those documents. However, this specification does not impose such a close relationship. For example, there may be collection URIs accepted by one of the two functions and not by the other; a collection might contain items that do not have any URI; or a URI collection might contain URIs that cannot be dereferenced to return any resource.

Thus, some implementations might ensure that calling fn:uri-collection and then applying fn:doc to each of the returned URIs delivers the same result as calling fn:collection with the same argument; however, this is not guaranteed.

In the case where fn:uri-collection returns the URIs of resources that could also be retrieved directly using fn:collection, there are several reasons why it might be appropriate to use this function in preference to the fn:collection function. For example:

It allows different URIs for different kinds of resource to be dereferenced in different ways: for example, the returned URIs might be referenced using the fn:unparsed-text function rather than the fn:doc function.
In XSLT 3.0 it allows the documents in a collection to be processed in streaming mode using the xsl:stream instruction.
It allows recovery from failures to read, parse, or validate individual documents, by calling the fn:doc (or other dereferencing) function within the scope of try/catch.
It allows selection of which documents to read based on their URI, for example they can be filtered to select those whose URIs end in .xml, or those that use the https scheme.
An application might choose to limit the number of URIs processed in a single run, for example it might process only the first 50 URIs in the collection; or it might present the URIs to the user and allow the user to select which of them need to be further processed.
It allows the URIs to be modified before they are dereferenced, for example by adding or removing query parameters, or by redirecting the request to a local cache or to a mirror site.

For some of these use cases, this assumes that the cost of calling fn:collection might be significant (for example, it might involving retrieving all the documents in the collection over the network and parsing them). This will not necessarily be true of all implementations.

14.6.5 fn:unparsed-text

Summary

The fn:unparsed-text function reads an external resource (for example, a file) and returns a string representation of the resource.

Signature

`fn:unparsed-text`(
`$href`	`as` `xs:string?`,
`$encoding`	`as` `xs:string?`	`:=` `()`
) `as` `xs:string?`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on static base URI.

Rules

The $href argument must be a string in the form of a URI reference, which must contain no fragment identifier, and must identify a resource for which a string representation is available. If the URI is a relative URI reference, then it is resolved relative to the static base URI property from the static context.

The mapping of URIs to the string representation of a resource is the mapping defined in the available text resources^XP31 component of the dynamic context.

If the $href argument is an empty sequence, the function returns an empty sequence.

The $encoding argument, if present and non-empty, is the name of an encoding. The values for this attribute follow the same rules as for the encoding attribute in an XML declaration. The only values which every implementation is required to recognize are utf-8 and utf-16.

The encoding of the external resource is determined as follows:

external encoding information is used if available, otherwise
if the media type of the resource is text/xml or application/xml (see [RFC 2376]), or if it matches the conventions text/*+xml or application/*+xml (see [RFC 7303] and/or its successors), then the encoding is recognized as specified in [Extensible Markup Language (XML) 1.0 (Fifth Edition)], otherwise
the $encoding argument is used if present, otherwise
the processor may use ·implementation-defined· heuristics to determine the likely encoding, otherwise
UTF-8 is assumed.

The result of the function is a string containing the string representation of the resource retrieved using the URI.

End-of-line characters are normalized as known from the Section 2.11 End-of-Line Handling^XML in [Extensible Markup Language (XML) 1.0 (Fifth Edition)], by translating both the two-character sequence x0D x0A and any x0D that is not followed by x0A to a single x0A character.

Error Conditions

A dynamic error is raised [err:FOUT1170] if the $href argument contains a fragment identifier, or if it cannot be resolved to an absolute URI (for example, because the base-URI property in the static context is absent), or if it cannot be used to retrieve the string representation of a resource.

A dynamic error is raised [err:FOUT1190] if the value of the $encoding argument is not a valid encoding name, if the processor does not support the specified encoding, if the string representation of the retrieved resource contains octets that cannot be decoded into Unicode ·characters· using the specified encoding, or if any resulting character is not a ·permitted character·.

A dynamic error is raised [err:FOUT1200] if $encoding is absent and the processor cannot infer the encoding using external information and the encoding is not UTF-8.

Notes

If it is appropriate to use a base URI other than the dynamic base URI (for example, when resolving a relative URI reference read from a source document) then it is advisable to resolve the relative URI reference using the fn:resolve-uri function before passing it to the fn:unparsed-text function.

There is no essential relationship between the sets of URIs accepted by the two functions fn:unparsed-text and fn:doc (a URI accepted by one may or may not be accepted by the other), and if a URI is accepted by both there is no essential relationship between the results (different resource representations are permitted by the architecture of the web).

There are no constraints on the MIME type of the resource.

The fact that the resolution of URIs is defined by a mapping in the dynamic context means that in effect, various aspects of the behavior of this function are ·implementation-defined·. Implementations may provide external configuration options that allow any aspect of the processing to be controlled by the user. In particular:

The set of URI schemes that the implementation recognizes is implementation-defined. Implementations may allow the mapping of URIs to resources to be configured by the user, using mechanisms such as catalogs or user-written URI handlers.
The handling of media types is implementation-defined.
Implementations may provide user-defined error handling options that allow processing to continue following an error in retrieving a resource, or in reading its content. When errors have been handled in this way, the function may return a fallback document provided by the error handler.
Implementations may provide user options that relax the requirement for the function to return deterministic results.

The rules for determining the encoding are chosen for consistency with [XML Inclusions (XInclude) Version 1.0 (Second Edition)]. Files with an XML media type are treated specially because there are use cases for this function where the retrieved text is to be included as unparsed XML within a CDATA section of a containing document, and because processors are likely to be able to reuse the code that performs encoding detection for XML external entities.

If the text file contains characters such as < and &, these will typically be output as < and & if the string is serialized as XML or HTML. If these characters actually represent markup (for example, if the text file contains HTML), then an XSLT stylesheet can attempt to write them as markup to the output file using the disable-output-escaping attribute of the xsl:value-of instruction. Note, however, that XSLT implementations are not required to support this feature.

Examples

This XSLT example attempts to read a file containing “boilerplate” HTML and copy it directly to the serialized output file:

<xsl:output method="html"/>

<xsl:template match="/">
  <xsl:value-of select="unparsed-text('header.html', 'iso-8859-1')"
                disable-output-escaping="yes"/>
  <xsl:apply-templates/>
  <xsl:value-of select="unparsed-text('footer.html', 'iso-8859-1')"
                disable-output-escaping="yes"/>
</xsl:template>

History

Changed in 4.0: end-of-line characters in the input are normalized.

14.6.6 fn:unparsed-text-lines

Summary

The fn:unparsed-text-lines function reads an external resource (for example, a file) and returns its contents as a sequence of strings, one for each line of text in the string representation of the resource.

Signature

`fn:unparsed-text-lines`(
`$href`	`as` `xs:string?`,
`$encoding`	`as` `xs:string?`	`:=` `()`
) `as` `xs:string*`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on static base URI.

Rules

The unparsed-text-lines function reads an external resource (for example, a file) and returns its string representation as a sequence of strings, separated at newline boundaries.

The result of the single-argument function is the same as the result of the expression fn:tokenize(fn:unparsed-text($href), '\n')[not(position()=last() and .='')]. The result of the two-argument function is the same as the result of the expression fn:tokenize(fn:unparsed-text($href, $encoding), '\n')[not(position()=last() and .='')].

The result is thus a sequence of strings containing the text of the resource retrieved using the URI, each string representing one line of text. End-of-line x0D is removed or converted to x0A following the rules of fn:unparsed-text. Newline characters xOA are not included in the returned strings. If there are two adjacent newline sequences, a zero-length string will be returned to represent the empty line; but if the external resource ends with a newline character, the result will be as if this final line ending were not present.

Error Conditions

Error conditions are the same as for the fn:unparsed-text function.

Notes

See the notes for fn:unparsed-text.

14.6.7 fn:unparsed-text-available

Summary

Because errors in evaluating the fn:unparsed-text function are non-recoverable, these two functions are provided to allow an application to determine whether a call with particular arguments would succeed.

Signature

`fn:unparsed-text-available`(
`$href`	`as` `xs:string?`,
`$encoding`	`as` `xs:string?`	`:=` `()`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on static base URI.

Rules

The fn:unparsed-text-available function determines whether a call on the fn:unparsed-text function with identical arguments would return a string.

If the first argument is an empty sequence, the function returns false.

In other cases, the function returns true if a call on fn:unparsed-text with the same arguments would succeed, and false if a call on fn:unparsed-text with the same arguments would fail with a non-recoverable dynamic error.

The functions fn:unparsed-text and fn:unparsed-text-available have the same requirement for ·determinism· as the functions fn:doc and fn:doc-available. This means that unless the user has explicitly stated a requirement for a reduced level of determinism, either of these functions if called twice with the same arguments during the course of a transformation must return the same results each time; moreover, the results of a call on fn:unparsed-text-available must be consistent with the results of a subsequent call on unparsed-text with the same arguments.

Notes

This requires that the fn:unparsed-text-available function should actually attempt to read the resource identified by the URI, and check that it is correctly encoded and contains no characters that are invalid in XML. Implementations may avoid the cost of repeating these checks for example by caching the validated contents of the resource, to anticipate a subsequent call on the fn:unparsed-text or fn:unparsed-text-lines function. Alternatively, implementations may be able to rewrite an expression such as if (unparsed-text-available(A)) then unparsed-text(A) else ... to generate a single call internally.

Since the function fn:unparsed-text-lines succeeds or fails under exactly the same circumstances as fn:unparsed-text, the fn:unparsed-text-available function may equally be used to test whether a call on fn:unparsed-text-lines would succeed.

14.6.8 fn:environment-variable

Summary

Returns the value of a system environment variable, if it exists.

Signature

`fn:environment-variable`(
`$name`	`as` `xs:string`
) `as` `xs:string?`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on environment variables.

Rules

The set of available environment variables^XP31 is a set of (name, value) pairs forming part of the dynamic context, in which the name is unique within the set of pairs. The name and value are arbitrary strings.

If the $name argument matches the name of one of these pairs, the function returns the corresponding value.

If there is no environment variable with a matching name, the function returns the empty sequence.

The collation used for matching names is ·implementation-defined·, but must be the same as the collation used to ensure that the names of all environment variables are unique.

The function is ·deterministic·, which means that if it is called several times within the same ·execution scope·, with the same arguments, it must return the same result.

Notes

On many platforms, the term “environment variable” has a natural meaning in terms of facilities provided by the operating system. This interpretation of the concept does not exclude other interpretations, such as a mapping to a set of configuration parameters in a database system.

Environment variable names are usually case sensitive. Names are usually of the form (letter|_) (letter|_|digit)*, but this varies by platform.

On some platforms, there may sometimes be multiple environment variables with the same name; in this case, it is implementation-dependent as to which is returned; see for example [POSIX.1-2008] (Chapter 8, Environment Variables). Implementations may use prefixes or other naming conventions to disambiguate the names.

The requirement to ensure that the function is deterministic means in practice that the implementation must make a snapshot of the environment variables at some time during execution, and return values obtained from this snapshot, rather than using live values that are subject to change at any time.

Operating system environment variables may be associated with a particular process, while queries and stylesheets may execute across multiple processes (or multiple machines). In such circumstances implementations may choose to provide access to the environment variables associated with the process in which the query or stylesheet processing was initiated.

Security advice: Queries from untrusted sources should not be permitted unrestricted access to environment variables. For example, the name of the account under which the query is running may be useful information to a would-be intruder. An implementation may therefore choose to restrict access to the environment, or may provide a facility to make fn:environment-variable always return the empty sequence.

14.6.9 fn:available-environment-variables

Summary

Returns a list of environment variable names that are suitable for passing to fn:environment-variable, as a (possibly empty) sequence of strings.

Signature

fn:available-environment-variables() as xs:string*

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on environment variables.

Rules

The function returns a sequence of strings, being the names of the environment variables in the dynamic context in some ·implementation-dependent· order.

The function is ·deterministic·: that is, the set of available environment variables does not vary during evaluation.

Notes

The function returns a list of strings, containing no duplicates.

It is intended that the strings in this list should be suitable for passing to fn:environment-variable.

See also the note on security under the definition of the fn:environment-variable function. If access to environment variables has been disabled, fn:available-environment-variables always returns the empty sequence.

15 Parsing and serializing

These functions convert between the lexical representation and XPath and XQuery data model representation of various file formats.

15.1 Functions on XML Data

These functions convert between the lexical representation of XML and the tree representation.

(The fn:serialize function also handles HTML and JSON output, but is included in this section for editorial convenience.)

Function	Meaning
`fn:parse-xml`	This function takes as input an XML document represented as a string, and returns the document node at the root of an XDM tree representing the parsed document.
`fn:parse-xml-fragment`	This function takes as input an XML external entity represented as a string, and returns the document node at the root of an XDM tree representing the parsed document fragment.
`fn:serialize`	This function serializes the supplied input sequence `$input` as described in [XSLT and XQuery Serialization 3.1], returning the serialized representation of the sequence as a string.

15.1.1 fn:parse-xml

Summary

This function takes as input an XML document represented as a string, and returns the document node at the root of an XDM tree representing the parsed document.

Signature

`fn:parse-xml`(
`$value`	`as` `xs:string?`
) `as` `document-node(element(*))?`

Properties

This function is ·nondeterministic·, ·context-dependent·, and ·focus-independent·. It depends on static base URI.

Rules

If $value is the empty sequence, the function returns the empty sequence.

The precise process used to construct the XDM instance is ·implementation-defined·. In particular, it is implementation-defined whether DTD and/or schema validation is invoked, and it is implementation-defined whether an XML 1.0 or XML 1.1 parser is used.

The static base URI property from the static context of the fn:parse-xml function call is used both as the base URI used by the XML parser to resolve relative entity references within the document, and as the base URI of the document node that is returned.

The document URI of the returned node is absent^DM40.

The function is not ·deterministic·: that is, if the function is called twice with the same arguments, it is ·implementation-dependent· whether the same node is returned on both occasions.

Error Conditions

A dynamic error is raised [err:FODC0006] if the content of $value is not a well-formed and namespace-well-formed XML document.

A dynamic error is raised [err:FODC0006] if DTD-based validation is carried out and the content of $value is not valid against its DTD.

Notes

Since the XML document is presented to the parser as a string, rather than as a sequence of octets, the encoding specified within the XML declaration has no meaning. If the XML parser accepts input only in the form of a sequence of octets, then the processor must ensure that the string is encoded as octets in a way that is consistent with rules used by the XML parser to detect the encoding.

The primary use case for this function is to handle input documents that contain nested XML documents embedded within CDATA sections. Since the content of the CDATA section are exposed as text, the receiving query or stylesheet may pass this text to the fn:parse-xml function to create a tree representation of the nested document.

Similarly, nested XML within comments is sometimes encountered, and lexical XML is sometimes returned by extension functions, for example, functions that access web services or read from databases.

A use case arises in XSLT where there is a need to preprocess an input document before parsing. For example, an application might wish to edit the document to remove its DOCTYPE declaration. This can be done by reading the raw text using the fn:unparsed-text function, editing the resulting string, and then passing it to the fn:parse-xml function.

Examples

The expression fn:parse-xml("<alpha>abcd</alpha>") returns a newly created document node, having an alpha element as its only child; the alpha element in turn is the parent of a text node whose string value is "abcd".

15.1.2 fn:parse-xml-fragment

Summary

This function takes as input an XML external entity represented as a string, and returns the document node at the root of an XDM tree representing the parsed document fragment.

Signature

`fn:parse-xml-fragment`(
`$value`	`as` `xs:string?`
) `as` `document-node()?`

Properties

This function is ·nondeterministic·, ·context-dependent·, and ·focus-independent·. It depends on static base URI.

Rules

If $value is the empty sequence, the function returns the empty sequence.

The input must be a namespace-well-formed external general parsed entity. More specifically, it must be a string conforming to the production rule extParsedEnt^XML in [Extensible Markup Language (XML) 1.0 (Fifth Edition)], it must contain no entity references other than references to predefined entities, and it must satisfy all the rules of [Namespaces in XML] for namespace-well-formed documents with the exception that the rule requiring it to be a well-formed document is replaced by the rule requiring it to be a well-formed external general parsed entity.

The string is parsed to form a sequence of nodes which become children of the new document node, in the same way as the content of any element is converted into a sequence of children for the resulting element node.

Schema validation is not invoked, which means that the nodes in the returned document will all be untyped.

The precise process used to construct the XDM instance is ·implementation-defined·. In particular, it is implementation-defined whether an XML 1.0 or XML 1.1 parser is used.

The static base URI from the static context of the fn:parse-xml-fragment function call is used as the base URI of the document node that is returned.

The document URI of the returned node is absent^DM40.

The function is not ·deterministic·: that is, if the function is called twice with the same arguments, it is ·implementation-dependent· whether the same node is returned on both occasions.

Error Conditions

A dynamic error is raised [err:FODC0006] if the content of $value is not a well-formed external general parsed entity, if it contains entity references other than references to predefined entities, or if a document that incorporates this well-formed parsed entity would not be namespace-well-formed.

Notes

See also the notes for the fn:parse-xml function.

The main differences between fn:parse-xml and fn:parse-xml-fragment are that for fn:parse-xml, the children of the resulting document node must contain exactly one element node and no text nodes, wheras for fn:parse-xml-fragment, the resulting document node can have any number (including zero) of element and text nodes among its children. An additional difference is that the text declaration at the start of an external entity has slightly different syntax from the XML declaration at the start of a well-formed document.

Note that all whitespace outside the text declaration is significant, including whitespace that precedes the first element node.

One use case for this function is to handle XML fragments stored in databases, which frequently allow zero-or-more top level element nodes. Another use case is to parse the contents of a CDATA section embedded within another XML document.

Examples

The expression `fn:parse-xml-fragment("<alpha>abcd</alpha><beta>abcd</beta>")` returns a newly created document node, having two elements named `alpha` and `beta` as its children; each of these elements in turn is the parent of a text node.
The expression `fn:parse-xml-fragment("He was <i>so</i> kind")` returns a newly created document node having three children: a text node whose string value is `"He was "`, an element node named `i` having a child text node with string value `"so"`, and a text node whose string value is `" kind"`.
The expression `fn:parse-xml-fragment("")` returns a document node having no children.
The expression `fn:parse-xml-fragment(" ")` returns a document node whose children comprise a single text node whose string value is a single space.
The expression `fn:parse-xml-fragment('<?xml version="1.0" encoding="utf8" standalone="yes"?><a/>')` results in a dynamic error [err:FODC0006] because the `standalone` keyword is not permitted in the text declaration that appears at the start of an external general parsed entity. (Thus, it is not the case that any input accepted by the `fn:parse-xml` function will also be accepted by `fn:parse-xml-fragment`.)

15.1.3 fn:serialize

Summary

This function serializes the supplied input sequence $input as described in [XSLT and XQuery Serialization 3.1], returning the serialized representation of the sequence as a string.

Signature

`fn:serialize`(
`$input`	`as` `item()*`,
`$options`	`as` `item()?`	`:=` `()`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The value of the first argument $input acts as the input sequence to the serialization process, which starts with sequence normalization.

The second argument $options, if present, provides serialization parameters. These may be supplied in either of two forms:

As an output:serialization-parameters element, having the format described in Section 3.1 Setting Serialization Parameters by Means of a Data Model Instance ^SER31. In this case the type of the supplied argument must match the required type element(output:serialization-parameters).
As a map. In this case the type of the supplied argument must match the required type map(*)

The single-argument version of this function has the same effect as the two-argument version called with $options set to an empty sequence. This in turn is the same as the effect of passing an output:serialization-parameters element with no child elements.

The final stage of serialization, that is, encoding, is skipped. If the serializer does not allow this phase to be skipped, then the sequence of octets returned by the serializer is decoded into a string by reversing the character encoding performed in the final stage.

If the second argument is omitted, or is supplied in the form of an output:serialization-parameters element, then the values of any serialization parameters that are not explicitly specified is ·implementation-defined·, and may depend on the context.

If the second argument is supplied as a map, then the ·option parameter conventions· apply. In this case:

Each entry in the map defines one serialization parameter.
The key of the entry is an xs:string value in the cases of parameter names defined in these specifications, or an xs:QName (with non-absent namespace) in the case of implementation-defined serialization parameters.
The required type of each parameter, and its default value, are defined by the following table. The default value is used when the map contains no entry for the parameter in question, and also when an entry is present, with the empty sequence as its value. The table also indicates how the value of the map entry is to be interpreted in cases where further explanation is needed.

Parameter	Required type	Interpretation	Default Value
`allow-duplicate-names`	`xs:boolean?`	`true()` means `"yes"`, `false()` means `"no"`	`no`
`byte-order-mark`	`xs:boolean?`	`true()` means `"yes"`, `false()` means `"no"`	`no`
`cdata-section-elements`	`xs:QName*`		`()`
`doctype-public`	`xs:string?`	Zero-length string and `()` both represent `"absent"`	absent
`doctype-system`	`xs:string?`	Zero-length string and `()` both represent `"absent"`	absent
`encoding`	`xs:string?`		`utf-8`
`escape-solidus`	`xs:boolean?`	`true()` means `"yes"`, `false()` means `"no"`	`yes`
`escape-uri-attributes`	`xs:boolean?`	`true()` means `"yes"`, `false()` means `"no"`	`yes`
`html-version`	`xs:decimal?`		`5`
`include-content-type`	`xs:boolean?`	`true()` means `"yes"`, `false()` means `"no"`	`yes`
`indent`	`xs:boolean?`	`true()` means `"yes"`, `false()` means `"no"`	`no`
`item-delimiter`	`xs:string?`		absent
`json-node-output-method`	`union(xs:string, xs:QName)?`	See Notes 1, 2	`xml`
`media-type`	`xs:string?`		(a media type suitable for the chosen `method`)
`method`	`union(xs:string, xs:QName)?`	See Notes 1, 2	`xml`
`normalization-form`	`xs:string?`		`none`
`omit-xml-declaration`	`xs:boolean?`	`true()` means `"yes"`, `false()` means `"no"`	`yes`
`standalone`	`xs:boolean?`	`true()` means `"yes"`, `false()` means `"no"`, `()` means `"omit"`	`omit`
`suppress-indentation`	`xs:QName*`		`()`
`undeclare-prefixes`	`xs:boolean?`	`true()` means `"yes"`, `false()` means `"no"`	`no`
`use-character-maps`	`map(xs:string, xs:string)?`	See Note 3	`map{}`
`version`	`xs:string?`		`1.0`

Notes to the table:

The notation union(A, B) is used to represent a union type whose member types are A and B.
If an xs:QName is supplied for the method or json-node-output-method options, then it must have a non-absent namespace URI. This means that system-defined serialization methods such as xml and json are defined as strings, not as xs:QName values.
For the use-character-maps option, the value is a map, whose keys are the characters to be mapped (as xs:string instances), and whose corresponding values are the strings to be substituted for these characters.

Error Conditions

A type error [err:XPTY0004]^XP occurs if the $options argument is present and does not match either of the types element(output:serialization-parameters)? or map(*).

Note:

This is defined as a type error so that it can be enforced via the function signature by implementations that generalize the type system in a suitable way.

If the host language makes serialization an optional feature and the implementation does not support serialization, then a dynamic error [err:FODC0010] is raised.

When the second argument is supplied as a map, and the supplied value is of the wrong type for the particular parameter, for example if the value of indent is a string rather than a boolean, then as defined by the ·option parameter conventions·, a type error [err:XPTY0004]^XP is raised. If the value is of the correct type, but does not satisfy the rules for that parameter defined in [XSLT and XQuery Serialization 3.1], then a dynamic error [err:SEPM0016]^SER31 is raised. (For example, this occurs if the map supplied to use-character-maps includes a key that is a string whose length is not one (1)).

If any serialization error occurs, including the detection of an invalid value for a serialization parameter as described above, this results in the fn:serialize call failing with a dynamic error.

Notes

One use case for this function arises when there is a need to construct an XML document containing nested XML documents within a CDATA section (or on occasions within a comment). See fn:parse-xml for further details.

Another use case arises when there is a need to call an extension function that expects a lexical XML document as input.

Another use case for this function is serializing instances of the data model into a human readable format for the purposes of debugging. Using the Section 10 Adaptive Output Method ^SER31 by specifying it as the output method defined in the second argument via output:serialization-parameters, allows for serializing any valid XDM instance without raising a serialization error.

There are also use cases where the application wants to post-process the output of a query or transformation, for example by adding an internal DTD subset, or by inserting proprietary markup delimiters such as the <% ... %> used by some templating languages.

The ability to specify the serialization parameters in an output:serialization-parameters element provides backwards compatibility with the 3.0 version of this specification; the ability to use a map takes advantage of new features in the 3.1 version. The default parameter values are implementation-defined when an output:serialization-parameters element is used (or when the argument is omitted), but are fixed by this specification in the case where a map (including an empty map) is supplied for the argument.

Examples

Variables

let $params := 
<output:serialization-parameters 
        xmlns:output="http://www.w3.org/2010/xslt-xquery-serialization">
  <output:omit-xml-declaration value="yes"/>
</output:serialization-parameters>

let $data := 
<a b="3"/>

Given the variables:
The following call might produce the output shown:
Expression:	`serialize($data, $params)`
Result:	'<a b="3"/>'
The following call would also produce the output shown (though the second argument could equally well be supplied as an empty map (`map{}`), since both parameters are given their default values):
Expression:	serialize( $data, map { "method": "xml", "omit-xml-declaration": true() } )
Result:	'<a b="3"/>'
The expression `fn:serialize(map{"a":"AB", "b": "BC"}, map{"method":"adaptive"})` returns `"map{"a":"AB","b":"BC"}"`
The expression `fn:serialize(array{"a",3, attribute test {"true"}}, map{"method":"adaptive"})` returns `"["a",3,test="true"]"`

15.2 Functions on HTML Data

These functions convert between the lexical representation of HTML and the tree representation.

Function	Meaning
`fn:parse-html`	This function takes as input an HTML document represented as a string, and returns the document node at the root of an XDM tree representing the parsed document.

15.2.1 XDM Mapping from HTML DOM Nodes

The HTML5 format is specified in [HTML: Living Standard]. This section describes facilities allowing HTML5 documents as defined by [DOM: Living Standard] HTML DOM nodes to be mapped to XDM accessors/nodes.

Note:

Because the [DOM: Living Standard] and [HTML: Living Standard] are not fixed, it is ·implementation-defined· which versions are used.

An implementation must match the semantics of the mapping described in this section, but the specific way it achieves that is ·implementation-dependent·.

Note:

An implementation may use the HTML DOM directly, using XDM accessor bindings for the HTML DOM nodes.

The [DOM: Living Standard] defines two parsing algorithms. The HTML parsing algorithm constructs a HTML DOM HTMLDocument document object for the HTML document. The XHTML parsing algorithm constructs a HTML DOM XMLDocument object for the HTML document, following XML parsing rules. This mapping supports both of these document types.

The [DOM: Living Standard] specification defines HTML DOM nodes that are mapped to XDM nodes as follows:

The HTML DOM Document interface maps to Section 5.1 Document nodes^DM40.
The HTML DOM Element interface maps to Section 5.2 Element nodes^DM40.
The HTML DOM Attr interface maps to Section 5.3 Attribute nodes^DM40.

HTML DOM Attr instances in an HTML DOM HTMLDocument that are namespace declarations are filtered out by this mapping. The XHTML parsing algorithm does not generate Attr nodes for namespace declarations.

Note:

If an implementation allows these nodes to be passed in via an API or similar mechanism, their behaviour is ·implementation-defined·.
The HTML DOM ProcessingInstruction interface maps to Section 5.5 Processing instruction nodes^DM40.

Note:

The HTML parsing algorithm does not support processing instructions. If encountered they are parsed as comment nodes. The HTML DOM ProcessingInstruction interface is for when the XHTML parsing algorithm is used, where the document is a valid XML document.
The HTML DOM Comment interface maps to Section 5.6 Comment nodes^DM40.
The HTML DOM Text interface maps to Section 5.7 Text nodes^DM40.

Note:

The HTML DOM CDATASection interface is an instance of HTML DOM Text, so CDATA sections also map to Section 5.7 Text nodes^DM40.

Adjacent HTML DOM Text nodes are combined into a single Section 5.7 Text nodes^DM40.

Note:

The HTML DOM DocumentFragment interface is not supported as an XML node. There are two places in the HTML DOM where this is used:

The HTML DOM ShadowRoot interface is not present in the main HTML DOM tree. It is only accessible via JavaScript.
The template element’s content property contains the child nodes of the template element. The behaviour of this is defined by the include-template-content key in the 15.2.2 HTML parser options map.

If an implementation allows these nodes to be passed in via an API or similar mechanism, their behaviour is ·implementation-defined·.

15.2.1.1 attributes Accessor

The result of the Section 4.1 attributes Accessor^DM40 dm:attributes($node) for an HTML DOM Node is as follows:

If the node is an instance of HTML DOM Element then the result is the value of the Element.attributes property mapped to a sequence as described below;
Otherwise, the result is an empty sequence.

The resulting HTML DOM NamedNodeMap is mapped to a sequence as follows:

NamedNodeMap.length is the length of the sequence, where a length of 0 results in an empty sequence;
NamedNodeMap.item(n) is the n^th element of the sequence.

That sequence is then filtered as follows:

If the Attr.namespaceURI property is "http://www.w3.org/2000/xmlns/", the attribute is not included in this sequence;
If the Attr.localName property is "xmlns", the attribute is not included in this sequence;
If the Attr.localName property starts with "xmlns:", the attribute is not included in this sequence;
Otherwise, the attribute is included in this sequence using the XDM mapping rules described in this section.

Note:

The HTML DOM Element.attributes property includes namespace and non-namespace attributes in the list when the HTML or XML parser is used. As such, the namespace attributes have to be filtered from the resulting XDM attribute sequence.

Note:

When the resulting document is an HTML DOM HTMLDocument, the Attr.localName and Attr.name properties of HTML DOM Attr nodes are both set to the qualified name. This includes namespace declarations which are filtered out by the logic in this section.

Note:

The Attr.localName property will be ASCII lowercase. The [HTML: Living Standard] section 13.2.5.33, Attribute name state specifies that ASCII upper alpha characters are appended to the attribute’s name in lowercase.

15.2.1.2 base-uri Accessor

The result of the Section 4.2 base-uri Accessor^DM40 dm:base-uri($node) for an HTML DOM Node is the value of the Node.baseURI property mapped as follows:

If the value is null or an empty string, then the result is an empty sequence;
Otherwise, the string value is cast to an xs:anyURI.

15.2.1.3 children Accessor

The result of the Section 4.3 children Accessor^DM40 dm:children($node) for an HTML DOM Node is as follows:

If the node is an instance of HTML DOM Document then the result is the value of the Node.childNodes property mapped to a sequence;
If the node is an instance of HTML DOM HTMLTemplateElement then the result is determined as follows:
1. If the include-template-content key of the parse-html-options map is false(), the result is an empty sequence;
2. Select the HTML DOM DocumentFragment from the HTMLTemplateElement.content property;
3. The HTML DOM DocumentFragment’s Node.childNodes property is mapped to a sequence;
If the node is an instance of HTML DOM Element then the result the value of the Node.childNodes property mapped to a sequence;
Otherwise, the result is an empty sequence.

The resulting HTML DOM NodeList is mapped to a sequence as follows:

NodeList.length is the length of the sequence, where a length of 0 results in an empty sequence;
NodeList.item(n) is the n^th element of the sequence.

That sequence is then filtered as follows:

If the child is an instance of HTML DOM DocumentType, that child is not included in this sequence;
If the child is an instance of HTML DOM Text, and the Node.previousSibling property value is also an instance of HTML DOM Text, that child is not included in this sequence;
Otherwise, the HTML DOM Node nodes are mapped to XDM according to the rules in this section.

Note:

Adjacent text nodes in the HTML DOM are treated as a single XDM text node by only including the first text node and providing logic to ensure that the text content is merged into a single text block.

15.2.1.4 document-uri Accessor

The result of the Section 4.4 document-uri Accessor^DM40 dm:document-uri($node) for an HTML DOM Node is as follows:

If the node is an instance of HTML DOM Document then the value of the Document.documentURI property mapped as follows:
1. If the value is null or an empty string, then the result is an empty sequence;
2. Otherwise, the string value is cast to an xs:anyURI.
Otherwise, the result is an empty sequence.

15.2.1.5 is-id Accessor

The result of the Section 4.5 is-id Accessor^DM40 dm:is-id($node) for an HTML DOM Node is as follows:

If the node is an instance of HTML DOM Attr then:
1. If the Attr.name property (its qualified name) is "id", then:
  1. If the Attr.value is castable to an xs:NCName, the result is true;
  2. Otherwise, the result is false;
2. Otherwise, the result is false;
Otherwise, the result is false.

Note:

In [HTML: Living Standard] section 3.2.5, Global attributes, the id attribute is defined as being unique in the element’s tree, containing at least one character, and not having any ASCII whitespace characters. This means that an HTML id attribute may not conform to an xs:NCName.

If an HTML id is not a valid xs:NCName then that attribute is not an XML ID.

15.2.1.6 is-idrefs Accessor

The result of the Section 4.6 is-idrefs Accessor^DM40 dm:is-idrefs($node) for an HTML DOM Node is an empty sequence.

15.2.1.7 namespace-nodes Accessor

The result of the Section 4.7 namespace-nodes Accessor^DM40 dm:namespace-nodes($node) for an HTML DOM Node is as follows:

If the node is an instance of HTML DOM Element then an ·implementation-dependent· sequence of namespace nodes that is sufficient to define the namespace context of the node.
Otherwise, the result is the empty sequence.

For the XHTML parsing algorithm, this will be equivalent to constructing the namespace nodes from an XML infoset, PSVI, or similar mapping.

For the HTML parsing algorithm, the [HTML: Living Standard] specification defines the namespace context in various places:

Section 2.1.3 XML compatibility defines the default element namespace to be http://www.w3.org/1999/xhtml.
Section 4.8.15 MathML defines rules for embedded MathML content in HTML documents. Section 13.1.2 Elements defines these elements as foreign elements, placing them in the MathML namespace (http://www.w3.org/1998/Math/MathML). The default element namespace for these elements is the MathML namespace.
Section 4.8.16 SVG defines rules for embedded SVG content in HTML documents. Section 13.1.2 Elements defines these elements as foreign elements, placing them in the SVG namespace (http://www.w3.org/2000/svg). The default element namespace for these elements is the SVG namespace.
Section 13.1.2.3 Attributes defines several namespaced attributes available on foreign elements. If any of these namespaced attributes are present, a namespace node for that namespace must be present on the element.

The supported namespace prefixes are:
1. xlink in the http://www.w3.org/1999/xlink namespace;
2. xml in the http://www.w3.org/XML/1998/namespace namespace; and
3. xmlns in the http://www.w3.org/2000/xmlns/ namespace.

No other namespaces are supported by the HTML parser.

15.2.1.8 nilled Accessor

The result of the Section 4.8 nilled Accessor^DM40 dm:nilled($node) for an HTML DOM Node is false().

15.2.1.9 node-kind Accessor

The result of the Section 4.9 node-kind Accessor^DM40 dm:node-kind($node) for an HTML DOM Node is as follows:

If the node is an instance of HTML DOM Document then the result is "document".
If the node is an instance of HTML DOM Element then the result is "element".
If the node is an instance of HTML DOM Attr then the result is "attribute".
If the node is an instance of HTML DOM ProcessingInstruction then the result is "processing-instruction".
If the node is an instance of HTML DOM Comment then the result is "comment".
If the node is an instance of HTML DOM Text then the result is "text".

15.2.1.10 node-name Accessor

The result of the Section 4.10 node-name Accessor^DM40 dm:node-name($node) for an HTML DOM Node is as follows:

If the node is an instance of HTML DOM Element then the result is determined as follows:
1. The local name is the value of the Element.localName property. This is derived as follows:
  1. The local name is initially set to the ASCII lowercase tag name. The [HTML: Living Standard] section 13.2.5.8, Tag name state specifies that ASCII upper alpha characters are appended to the element’s name in lowercase.
  2. If the local name is an SVG element name, the case-sensitive name is used. [HTML: Living Standard] section 13.2.6.5, The rules for parsing tokens in foreign content has a table mapping the lowercase element names to their SVG names.
  3. If the local name contains a character that is not a valid XML NameStartChar or NameChar, then an ·implementation-defined· replacement string is used. The result must be a valid NCName.
    
    Note:
    
    [DOM: Living Standard] section 13.2.9 Coercing an HTML DOM into an infoset uses a Unnnnnn escape sequence. That would map : to U00003A.
    
    This local name escaping applies only to the HTML parsing algorithm. If the XHTML parsing algorithm is used, the localName and prefix will be correctly set for QName-based node names.
2. The namespace prefix is the value of the Element.prefix property, or empty if the value is null;
3. The namespace URI is the value of the Element.namespaceURI property, or empty if the value is null.
  1. If the element is an HTML element, the namespace URI is "http://www.w3.org/1999/xhtml".
  2. If the element is an SVG element, the namespace URI is "http://www.w3.org/2000/svg".
  3. If the element is a MathML element, the namespace URI is "http://www.w3.org/1998/Math/MathML".
If the node is an instance of HTML DOM Attr then the result is determined as follows:
1. The attribute name is the tokenized attribute name. The [HTML: Living Standard] section 13.2.5.33, Attribute name state specifies that ASCII upper alpha characters are appended to the attribute’s name in lowercase.
2. The local name is the value of the Attr.localName property. This is derived as follows:
  1. The local name is initially set to the attribute name.
  2. If the local name is an SVG or MathML attribute name, the case-sensitive name is used. [HTML: Living Standard] section 13.2.6.1, Creating and inserting nodes has a table mapping the lowercase attribute names to their SVG/MathML names.
  3. If the local name is an allowed xlink, xml, or xmlns attribute name the local name is the value of the local name column of the attribute name mapping table in [HTML: Living Standard] section 13.2.6.1, Creating and inserting nodes.
  4. If the local name contains a character that is not a valid XML NameStartChar or NameChar, then an ·implementation-defined· replacement string is used. The result must be a valid NCName.
    
    Note:
    
    [DOM: Living Standard] section 13.2.9 Coercing an HTML DOM into an infoset uses a Unnnnnn escape sequence. That would map : to U00003A.
    
    This local name escaping applies only to the HTML parsing algorithm. If the XHTML parsing algorithm is used, the localName and prefix will be correctly set for QName-based node names.
3. The namespace prefix is the value of the Attr.prefix property, or empty if the value is null.
  1. If the attribute name is an allowed xlink, xml, or xmlns attribute name the namespace prefix is the value of the prefix column of the attribute name mapping table in [HTML: Living Standard] section 13.2.6.1, Creating and inserting nodes.
4. The namespace URI is the value of the Attr.namespaceURI property, or empty if the value is null;
  1. If the attribute name is an allowed xlink, xml, or xmlns attribute name the namespace URI is the value of the namespace column of the attribute name mapping table in [HTML: Living Standard] section 13.2.6.1, Creating and inserting nodes.
If the node is an instance of HTML DOM ProcessingInstruction then the result is an xs:QName constructed as follows:
1. The local name is the value of the ProcessingInstruction.target property;
2. The namespace prefix is empty;
3. The namespace URI is empty;
Otherwise, the result is an empty sequence.

Note:

When the resulting document is an HTML DOM HTMLDocument, the Element.localName and Element.name properties of HTML DOM Element nodes are both set to the qualified name.

Note:

When the resulting document is an HTML DOM HTMLDocument, the Attr.localName and Attr.name properties of HTML DOM Attr nodes are both set to the qualified name.

15.2.1.11 parent Accessor

The result of the Section 4.11 parent Accessor^DM40 dm:parent($node) for an HTML DOM Node is as follows:

Let $parent be the Node.parentNode property of the node;
If $parent is an instance of HTML DOM DocumentFragment, then for each HTML DOM HTMLTemplateElement $template in the parsed DOM tree:
1. Let $content be the value of the HTMLTemplateElement.content property of $template;
2. If $content is the same node as $parent, then the result is $template using the XDM mapping rules described in this section;
3. If there are no more $template nodes, then the result is an empty sequence;
If $parent is null, then the result is an empty sequence;
Otherwise, the result is $parent using the XDM mapping rules described in this section.

Note:

The current node can have a HTML DOM DocumentFragment parent node only if the include-template-content key of the html-parser-options is true().

Note:

The HTML DOM DocumentFragment’s Node.parentNode property is null, and a DocumentFragment attached to HTMLTemplateElement.content property does not have a host property connecting the fragment back to the template element.

If a future version of [DOM: Living Standard] adds a DocumentFragment.host property that references the node’s template element, or the implementation has access to that internal property, the implementation may choose to use that instead of traversing the parsed HTML tree.

15.2.1.12 string-value Accessor

The result of the Section 4.12 string-value Accessor^DM40 dm:string-value($node) for an HTML DOM Node is as follows:

If the node is an instance of HTML DOM Document, then use the algorithm described in 15.2.1.12.1 Tree string construction;
If the node is an instance of HTML DOM Element, then use the algorithm described in 15.2.1.12.1 Tree string construction;
If the node is an instance of HTML DOM Text, then use the algorithm described in 15.2.1.12.2 Text node string construction;
Otherwise, the result is the value of the Node.nodeValue property.

15.2.1.12.1 Tree string construction

The following algorithm is used to construct the concatenated string value of a node in the HTML DOM tree:

Let $text be the string value "";
For each descendant node $node in document order:
1. If $node is not an instance of HTML DOM Text, process the next node in document order;
2. Append the value of the Node.nodeValue property for $node to $text;
The result is $text.

15.2.1.12.2 Text node string construction

The following algorithm is used to construct the maximal sequence of adjacent character information items for text node children of an element:

Let $text be the string value "";
Append the value of the Node.nodeValue property for $node to $text;
Let $next be the value of Node.nextSibling;
Let $next is null, or not an instance of HTML DOM Text, the result is $text;
Otherwise, repeat from step 2 using $next as $node.

Note:

Adjacent text nodes in the HTML DOM are treated as a single XDM text node by only including the first text node and providing logic to ensure that the text content is merged into a single text block.

15.2.1.13 type-name Accessor

The result of the Section 4.13 type-name Accessor^DM40 dm:type-name($node) for an HTML DOM Node is as follows:

If the node is an instance of HTML DOM Element then the result is xs:untyped.
If the node is an instance of HTML DOM Attr then the result is xs:untypedAtomic.
If the node is an instance of HTML DOM Text then the result is xs:untypedAtomic.
Otherwise, the result is an empty sequence.

15.2.1.14 typed-value Accessor

The result of the Section 4.14 typed-value Accessor^DM40 dm:typed-value($node) for an HTML DOM Node is as follows:

Let $string-value be the 15.2.1.12 string-value Accessor for the node;
If the node is an instance of HTML DOM Document then the result is $string-value as an xs:untypedAtomic;
If the node is an instance of HTML DOM Element then the result is $string-value as an xs:untypedAtomic;
If the node is an instance of HTML DOM Attr then the result is $string-value as an xs:untypedAtomic;
If the node is an instance of HTML DOM Text then the result is $string-value as an xs:untypedAtomic;
Otherwise, the result is $string-value.

15.2.1.15 unparsed-entity-public-id Accessor

The result of the Section 4.15 unparsed-entity-public-id Accessor^DM40 dm:unparsed-entity-public-id($node) for an HTML DOM Node is an empty sequence.

15.2.1.16 unparsed-entity-system-id Accessor

The result of the Section 4.16 unparsed-entity-system-id Accessor^DM40 dm:unparsed-entity-system-id($node) for an HTML DOM Node is an empty sequence.

15.2.2 HTML parser options

This section describes the record structure used to pass options to the fn:parse-html function.

`parse-html-options`:
`record(`
`method`	`as` `union(enum("html", "xhtml"), xs:string)`,
`html-version`	`as` `union(enum("LS"), xs:decimal)`,
`encoding?`	`as` `xs:string?`,
`include-template-content?`	`as` `xs:boolean?`,
`*`
`)`

The keys of this record type are:

The parse-html options record
method	The approach used to parse the HTML document into XDM nodes. Note: An implementation may use this to specify a specific algorithm, tool, or library that is used, such as `tidy` or `tagsoup`. An implementation may also use this to specify a non-standard variant of HTML to support, such as `word` for the Microsoft Word HTML variant.
html-version	The version of HTML to support when parsing HTML strings or sequences of octets. Valid values an implementation must support for the `html` method are: `3`, `3.2` for HTML 3.2 W3C Recommendation, 14 January 1997 `4`, `4.01` for HTML 4.01 W3C Recommendation, 24 December 1999 `5.0` for HTML5 W3C Recommendation, 28 October 2014 `5.1` for HTML 5.1 W3C Recommendation, 1 November 2016 `5.2` for HTML 5.2 W3C Recommendation, 14 December 2017 `LS` for HTML Living Standard, WHATWG `5` may be equivalent to any of `5.0`, `5.1`, `5.2`, or `LS` Valid values an implementation must support for the `xhtml` method are: `1.0` for XHTML 1.0 W3C Recommendation, 26 January 2000 `1.1` for XHTML 1.1 W3C Recommendation, 31 May 2001 Any other `method` and `html-version` combinations are ·implementation-defined·.
encoding	The character encoding to use to decode a sequence of octets that represents an HTML document.
include-template-content	Defines how to handle elements in the `HTMLTemplateElement.content` property. If this option is `true()`, the `template` element’s children are the children of the `content` property’s document fragment node. If this option is `false()`, the `template` element’s children are the empty sequence. The default behaviour is ·implementation-defined·. Note: This allows an implementation to support the behaviour defined in [HTML: Living Standard] section 4.12.3.1, Interaction of `template` elements with XSLT and XPath: This option would default to `true()` for an XSLT processor operating on an HTML DOM constructed from an XHTML document. This option would default to `false()` for an XPath processor using the [DOM: Living Standard] section 8, XPath APIs.
*	Additional ·implementation-defined· parser options. Example: An implementation may provide keys for options to the tidy HTML parser, allowing a user to configure the behaviour of that parser.

15.2.3 fn:parse-html

Summary

This function takes as input an HTML document represented as a string, and returns the document node at the root of an XDM tree representing the parsed document.

Signature

`fn:parse-html`(
`$html`	`as` `union(xs:string, xs:hexBinary, xs:base64Binary)?`,
`$options`	`as` `parse-html-options`	`:=` `map{ "method":"html", "html-version":"5" }`
) `as` `document-node(element(*:html))?`

Properties

This function is ·nondeterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $html is the empty sequence the function returns the empty sequence.

If $html is not the empty sequence, an input byte stream is constructed as follows:

If $html is an xs:string, the encoding of the input byte stream is determined in a way consistent with [HTML: Living Standard] section 13.2.3.1, Parsing with a known character encoding to generate the bytes for that string. The specific character encoding is the ·implementation-dependent· encoding corresponding to the implementation's string representation.
If the type of $html is a sequence of octets (xs:hexBinary or xs:base64Binary) the encoding of the input byte stream is determined in a way consistent with [HTML: Living Standard] section 13.2.3.2, Determining the character encoding:
1. The encoding key of $options is used in step 2 of Determining the character encoding as the user instructing the user agent to override the document’s character encoding with the specified encoding.
2. If the encoding key of $options is not specified, step 2 of Determining the character encoding is skipped.

The resulting byte stream is then used to construct an XDM representation of the HTML document in an ·implementation-dependent· way that is equivalent to:

Tokenizing the byte stream according to the HTML parsing algorithm determined by the method and html-version keys of $options (see below). For {"method": "html", "html-version": "LS"} this will be equivalent to [HTML: Living Standard] section 13.2.5, Tokenization.
Constructing a HTMLDocument object for HTML documents, or an XMLDocument for XML/XHTML documents according to the method's tree construction algorithm from the tokens. For {"method": "html", "html-version": "LS"} this will be equivalent to [HTML: Living Standard] section 13.2.6, Tree construction.
Building an XDM representation of the HTMLDocument or XMLDocument according to the 15.2.1 XDM Mapping from HTML DOM Nodes.

For any given method key of $options the implementation must use a parser and validator consistent with the html-version key of $options. These are:

Valid method and html version combinations
method	html-version	Description
html	3, 3.2, 4, 4.01	An ·implementation-dependent· parsing algorithm, tree construction, and validation consistent with the specified HTML version.
html	5, 5.0, 5.1, 5.2	An HTML5 conformant parsing algorithm, tree construction, and validation consistent with the specified HTML version. An implementation may choose to use `LS` for all these HTML versions.
html	LS	A parsing algorithm, tree construction, and validation consistent with the [HTML: Living Standard].
xhtml	1.0, 1.1	An implementation may choose to use an XML parser to directly construct the XDM nodes, and then use an ·implementation-dependent· validation mechanism (such as DTD or XMLSchema) to validate the XHTML DOM tree. An implementation may also choose to use [HTML: Living Standard] for all these XHTML versions, or some other HTML parser capable of processing XHTML documents.
*	*	An ·implementation-defined· parsing algorithm, tree construction, and validation consistent with the specified HTML version. This allows an implementation to provide their own `method` and `html-version` combinations. For example, an implementation could use the values `"whatwg"` and `"2023-01-28"` for an implementation of the WHATWG HTML Living Standard at a given date.

The function is not ·deterministic·: that is, if the function is called twice with the same arguments, it is ·implementation-dependent· whether the same node is returned on both occasions.

Error Conditions

A dynamic error is raised [err:FODC0011] if the content of $html is not a well-formed HTML document.

A dynamic error is raised [err:FODC0012] if the method key of $options is not supported by the implementation.

A dynamic error is raised [err:FODC0012] if a key passed to $options, or the value of that key, is not supported by the implementation.

Notes

If the HTML parser accepts a string as the input then that may be used directly when $html is an xs:string instead of converting the string to a sequence of octets in an ·implementation-dependent· encoding. The HTML parser must not perform character encoding processing on that input, treating the HTML string as being in a known character encoding that matches the encoding of the string.

The mapping from the HTML document to the XDM nodes can be done in several ways:

An implementation could construct the XDM nodes directly in the HTML tree construction step of the HTML parsing algorithm.
An implementation could take the DOM tree and interfaces generated by the HTML parser and adapt those to the XDM accessors. The 15.2.1 XDM Mapping from HTML DOM Nodes section defines this for the [DOM: Living Standard] specification.
An implementation could traverse the HTML document returned by the parsing algorithm and create the corresponding XDM nodes.

The WHATWG Encoding specification defines the ISO 8859-1 (latin1) and ASCII encodings as aliases of the windows-1252 encoding.

Examples

The expression `parse-html(())` returns `()`.
The expression `parse-html("<p>Hello</p>")` returns an XDM document node for a HTML document with a single paragraph within the body element.
The expression `parse-html("<p>Hi</p>", method:="html")` is equivalent to `parse-html("<p>Hi</p>")`.
The expression `parse-html($html, method:="tidy")` could use the tidy application or library to parse `$html` if supported by the implementation. Otherwise an [err:FODC0012] error is raised.
The expression `parse-html($html, method:="tagsoup", nons:=true())` could use the tagsoup application to parse `$html` if supported by the implementation, passing the `--nons` argument to the application.
[TODO: The examples depend on keyword arguments.]

History

New in 4.0. Accepted 2023-01-10.

15.3 Functions on JSON Data

The functions listed in this section parse or serialize JSON data.

JSON is a popular format for exchange of structured data on the web: it is specified in [RFC 7159]. This section describes facilities allowing JSON data to be converted to and from XDM values.

This specification describes two ways of representing JSON data losslessly using XDM constructs. The first method uses XDM maps to represent JSON objects, and XDM arrays to represent JSON arrays. The second method represents all JSON constructs using XDM element and attribute nodes.

Function	Meaning
`fn:parse-json`	Parses a string supplied in the form of a JSON text, returning the results typically in the form of a map or array.
`fn:json-doc`	Reads an external resource containing JSON, and returns the result of parsing the resource as JSON.
`fn:json-to-xml`	Parses a string supplied in the form of a JSON text, returning the results in the form of an XML document node.
`fn:xml-to-json`	Converts an XML tree, whose format corresponds to the XML representation of JSON defined in this specification, into a string conforming to the JSON grammar.
`fn:json`	Creates a JSON representation of an arbitrary XDM value.
`fn:pin`	Adapts a map or array so that retrieval operations retain additional information.
`fn:label`	Returns the label associated with a labeled item, as a map.

Note also that the function fn:serialize has an option to act as the inverse function to fn:parse-json.

15.3.1 Representing JSON using maps and arrays

This section defines a mapping from JSON data to XDM maps and arrays. Two functions are available to support this mapping: fn:parse-json and fn:serialize (with options selecting JSON as the output method). The fn:parse-json function will accept any JSON text as input, and converts it to XDM data values. The fn:serialize function (with JSON as the output method) will accept any XDM value produced using fn:parse-json and convert it back to the original JSON text (subject to insignificant variations such as reordering the properties in a JSON object).

Note:

The conversion is lossless if recommended JSON good practice is followed. Information may however be lost if (a) JSON numbers are not exactly representable as double-precision floating point, or (b) duplicate key values appear within a JSON object.

The representation of JSON data produced by the fn:parse-json function has been chosen with ease of manipulation as a design aim. For example, a simple JSON object such as {"Sun":1, "Mon":2, "Tue":3, ...} produces a simple map, so if the result of parsing is held in $weekdays, the number for a given weekday can be extracted using an expression such as $weekdays?Tue. Similarly, a simple array such as ["Sun", "Mon", "Tue", ...] produces an array that can be addressed as, for example, $weekdays(3). A more deeply nested structure can be addressed in a similar way: for example if the JSON text is an array of person objects, each of which has a property named phones which is an array of strings containing phone numbers, then the first phone number of each person in the data can be addressed as $data?phones(1).

15.3.2 XML Representation of JSON

This section defines a mapping from JSON data to XML (specifically, to XDM element and attribute nodes). A function fn:json-to-xml is provided to take a JSON string as input and convert it to the XML representation, and a second function fn:xml-to-json performs the reverse operation.

The XML representation is designed to be capable of representing any valid JSON text including one that uses characters which are not valid in XML. The transformation is normally lossless: that is, distinct JSON texts convert to distinct XML representations. When converting JSON to XML, options are provided to reject unsupported characters, to replace them with a substitute character, or to leave them in backslash-escaped form.

Note:

The following example demonstrates the correspondence of a JSON text and the corresponding XML representation.

Example: A JSON Text and its XML Representation

Consider the following JSON text:

{
    "desc"    : "Distances between several cities, in kilometers.",
    "updated" : "2014-02-04T18:50:45",
    "uptodate": true,
    "author"  : null,
    "cities"  : {
        "Brussels": [
                      {"to": "London",    "distance": 322},
                      {"to": "Paris",     "distance": 265},
                      {"to": "Amsterdam", "distance": 173}
                    ],
        "London": [
                      {"to": "Brussels",  "distance": 322},
                      {"to": "Paris",     "distance": 344},
                      {"to": "Amsterdam", "distance": 358}
                  ],
        "Paris": [
                      {"to": "Brussels",  "distance": 265},
                      {"to": "London",    "distance": 344},
                      {"to": "Amsterdam", "distance": 431}
                 ],
        "Amsterdam": [
                      {"to": "Brussels",  "distance": 173},
                      {"to": "London",    "distance": 358},
                      {"to": "Paris",     "distance": 431}
                     ]
     }
}

The XML representation of this text is as follows. Whitespace is included in the XML representation for purposes of illustration, but it will not necessarily be present in the output of the json-to-xml function.

  <map xmlns="http://www.w3.org/2005/xpath-functions">
    <string key='desc'>Distances between several cities, in kilometers.</string>
    <string key='updated'>2014-02-04T18:50:45</string>
    <boolean key="uptodate">true</boolean>
    <null key="author"/>
    <map key='cities'>
      <array key="Brussels">
        <map>
            <string key="to">London</string>
            <number key="distance">322</number>
        </map>
        <map>
            <string key="to">Paris</string>
            <number key="distance">265</number>
        </map>
        <map>
            <string key="to">Amsterdam</string>
            <number key="distance">173</number>
        </map>
      </array>
      <array key="London">
        <map>
            <string key="to">Brussels</string>
            <number key="distance">322</number>
        </map>
        <map>
            <string key="to">Paris</string>
            <number key="distance">344</number>
        </map>
        <map>
            <string key="to">Amsterdam</string>
            <number key="distance">358</number>
        </map>
      </array>
      <array key="Paris">
        <map>
            <string key="to">Brussels</string>
            <number key="distance">265</number>
        </map>
        <map>
            <string key="to">London</string>
            <number key="distance">344</number>
        </map>
        <map>
            <string key="to">Amsterdam</string>
            <number key="distance">431</number>
        </map>
      </array>
      <array key="Amsterdam">
        <map>
            <string key="to">Brussels</string>
            <number key="distance">173</number>
        </map>
        <map>
            <string key="to">London</string>
            <number key="distance">358</number>
        </map>
        <map>
            <string key="to">Paris</string>
            <number key="distance">431</number>
        </map>
      </array>
    </map>
  </map>

An XSD 1.0 schema for the XML representation is provided in C.2 Schema for the result of fn:json-to-xml. It is not necessary to import this schema into the static context unless the stylesheet or query makes explicit reference to the components defined in the schema. If the stylesheet or query does import a schema for the namespace http://www.w3.org/2005/xpath-functions, then:

Unless the host language specifies otherwise, the processor (if it is schema-aware) must recognize an import declaration for this namespace, whether or not a schema location is supplied.
If a schema location is provided, then the schema document at that location must be equivalent to the schema document at C.2 Schema for the result of fn:json-to-xml; the effect if it is not equivalent is ·implementation-dependent·

The rules governing the mapping from JSON to XML are as follows. In these rules, the phrase “an element named N” is to be interpreted as meaning “an element node whose local name is N and whose namespace URI is http://www.w3.org/2005/xpath-functions”.

The JSON value null is represented by an element named null, with empty content.
The JSON values true and false are represented by an element named boolean, with content conforming to the type xs:boolean. When the element is created by the fn:json-to-xml function, the string value of the element will be true or false. The fn:xml-to-json function also recognizes other strings that validate as xs:boolean, for example 1 and 0. Leading and trailing whitespace is accepted.
A JSON number is represented by an element named number, with content conforming to the type xs:double, with the additional restriction that the value must not be positive or negative infinity, nor NaN. The fn:json-to-xml function creates an element whose string value is lexically the same as the JSON representation of the number. The fn:xml-to-json function generates a JSON representation that is the result of casting the (typed or untyped) value of the node to xs:double and then casting the result to xs:string. Leading and trailing whitespace is accepted. Since JSON does not impose limits on the range or precision of numbers, these rules mean that conversion from JSON to XML will always succeed, and will retain full precision in the lexical representation unless the data model implementation is one that reconstructs the string value from the typed value. In the reverse direction, conversion from XML to JSON may fail if the value is infinity or NaN, or if the string value is such that casting to xs:double produces positive or negative infinity.
A JSON string is represented by an element named string, with content conforming to the type xs:string. The string element has two alternative representations: escaped form, and unescaped form.
A JSON array is represented by an element named array. The content is a sequence of child elements representing the members of the array in order, each such element being the representation of the array member obtained by applying these rules recursively.
A JSON object is represented by an element named map. The content is a sequence of child elements each of which represents one of the name/value pairs in the object. The representation of the name/value pair N:V is obtained by taking the element that represents the value V (by applying these rules recursively) and adding an attribute with name key (in no namespace), whose value is N as an instance of xs:string. The functions fn:json-to-xml and fn:xml-to-json both retain the order of entries, subject to rules about how duplicate keys are handled. The key may be represented in escaped or unescaped form.

The attribute escaped="true" may be specified on a string element to indicate that the string value contains backslash-escaped characters that are to be interpreted according to the JSON rules. The attribute escaped-key="true" may be specified on any element with a key attribute to indicate that the key contains backslash-escaped characters that are to be interpreted according to the JSON rules. Both attributes have the default value false, signifying that the relevant value is in unescaped form. In unescaped form, the backslash character has no special significance (it represents itself).

The JSON grammar for number is a subset of the lexical space of the XSD type xs:double. The mapping from JSON number values to xs:double values is defined by the XPath rules for casting from xs:string to xs:double. Note that these rules will never generate an error for out-of-range values; instead very large or very small values will be converted to +INF or -INF. Since JSON does not impose limits on the range or precision of numbers, the conversion is not guaranteed to retain full precision.

Although the order of entries in a JSON object is generally considered to have no significance, the functions json-to-xml and json-to-xml both retain order.

The XDM representation of a JSON value may either be untyped (all elements annotated as xs:untyped, attributes as xs:untypedAtomic), or it may be typed. If it is typed, then it must have the type annotations obtained by validating the untyped representation against the schema given in C.2 Schema for the result of fn:json-to-xml. If it is untyped, then it must be an XDM instance such that validation against this schema would succeed; with the proviso that all attributes other than those in no namespace or in namespace http://www.w3.org/2005/xpath-functions are ignored, including attributes such as xsi:type and xsi:nil that would normally influence the process of schema validation.

The namespace prefix associated with the namespace http://www.w3.org/2005/xpath-functions (if any) is immaterial. The effect of the fn:xml-to-json function does not depend on the choice of prefix, and the prefix (if any) generated by the fn:json-to-xml function is ·implementation-dependent·.

15.3.3 fn:parse-json

Summary

Parses a string supplied in the form of a JSON text, returning the results typically in the form of a map or array.

Signature

`fn:parse-json`(
`$value`	`as` `xs:string?`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `item()?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If the second argument is omitted or an empty sequence, the result is the same as calling the two-argument form with an empty map as the value of the $options argument.

The first argument is a JSON text as defined in [RFC 7159], in the form of a string. The function parses this string to return an XDM value.

If $value is the empty sequence, the function returns the empty sequence.

Note:

The result will also be an empty sequence if $value is the string "null".

The $options argument can be used to control the way in which the parsing takes place. The ·option parameter conventions· apply.

The entries that may appear in the $options map are as follows:

Key	Value	Meaning
`liberal`	Determines whether deviations from the syntax of RFC7159 are permitted. Type: `xs:boolean` Default: `false`
	`false`	The input must consist of an optional byte order mark (which is ignored) followed by a string that conforms to the grammar of `JSON-text` in [RFC 7159]. An error must be raised [err:FOJS0001] if the input does not conform to the grammar.
	`true`	The input may contain deviations from the grammar of [RFC 7159], which are handled in an ·implementation-defined· way. (Note: some popular extensions include allowing quotes on keys to be omitted, allowing a comma to appear after the last item in an array, allowing leading zeroes in numbers, and allowing control characters such as tab and newline to be present in unescaped form.) Since the extensions accepted are implementation-defined, an error may be raised [err:FOJS0001] if the input does not conform to the grammar.
`duplicates`	Determines the policy for handling duplicate keys in a JSON object. To determine whether keys are duplicates, they are compared using the Unicode codepoint collation, after expanding escape sequences, unless the `escape` option is set to `true`, in which case keys are compared in escaped form. Type: `xs:string` Default: `use-first`
	`reject`	An error is raised [err:FOJS0003] if duplicate keys are encountered.
	`use-first`	If duplicate keys are present in a JSON object, all but the first of a set of duplicates are ignored.
	`use-last`	If duplicate keys are present in a JSON object, all but the last of a set of duplicates are ignored.
`escape`	Determines whether special characters are represented in the XDM output in backslash-escaped form. Type: `xs:boolean` Default: `true`
	`false`	All characters in the input that are valid in the version of XML supported by the implementation, whether or not they are represented in the input by means of an escape sequence, are represented as unescaped characters in the result. Any characters or codepoints that are not valid XML characters (for example, unpaired surrogates) are passed to the `fallback` function as described below; in the absence of a fallback function, they are replaced by the Unicode `REPLACEMENT CHARACTER` (`xFFFD`).
	`true`	JSON escape sequences are used in the result to represent special characters in the JSON input, as defined below, whether or not they were represented using JSON escape sequences in the input. The characters that are considered “special” for this purpose are: all codepoints in the range `x00` to `x1F` or `x7F` to `x9F`; all codepoints that do not represent characters that are valid in the version of XML supported by the processor, including codepoints representing unpaired surrogates; the backslash character itself (`x5C`). Such characters are represented using a two-character escape sequence where available (for example, `\t`), or a six-character escape sequence otherwise (for example `\uDEAD`). Characters other than these are not escaped in the result, even if they were escaped in the input.
`fallback`	Provides a function which is called when the input contains an escape sequence that represents a character that is not valid in the version of XML supported by the implementation. It is an error to supply the `fallback` option if the `escape` option is present with the value `true`. Type: `(function(xs:string) as xs:anyAtomicType)?` Default: `fn { char(0xFFFD) }`
`fallback`	`User-supplied function`	The function is called when the JSON input contains a special character (as defined under the `escape` option) that is valid according to the JSON grammar (whether the special character is represented in the input directly or as an escape sequence), but which does not represent a character that is valid in the version of XML supported by the processor. It is called once for any surrogate that is not properly paired with another surrogate. The untyped atomic value supplied as the argument will always be a two- or six-character escape sequence, starting with a backslash, that conforms to the rules in the JSON grammar (as extended by the implementation if `liberal:true()` is specified): for example `\b` or `\uFFFF` or `\uDEAD`. By default, the escape sequence is replaced with the Unicode `REPLACEMENT CHARACTER`. The function is not called for an escape sequence that is invalid against the grammar (for example `\x0A`). The string, which results from invoking `fn:string` on the result of the function, is inserted into the result in place of the invalid character. The function also has the option of raising a dynamic error by calling `fn:error`.
`null`	Determines how the JSON `null` value should be represented. Type: `item()` Default:* `()`
`null`	`Value`	The supplied XDM value is used to represent the JSON `null` value. The default representation of `null` is an empty sequence, which works well in cases where setting a property of an object to `null` has the same meaning as omitting the property. It works less well in cases where `null` is used with some other meaning, because expressions such as the lookup operators `?` and `??` flatten the result to a single sequence of items, which means that any entries whose value is an empty sequence effectively disappear. The property can be set to any XDM value; a suggested value is the `xs:QName` value `fn:QName("http://www.w3.org/2005/xpath-functions", "null")`, which is recognized by the JSON serialization method as representing the JSON value `null`.
`number-parser`	Determines how numeric values should be processed. Type: `(function(xs:untypedAtomic) as item()?)?` Default: `xs:double#1`
`number-parser`	`User-supplied function`	The supplied function is called to process the string value of any JSON number in the input. By default, numbers are processed by converting to `xs:double` using the XPath casting rules. Supplying the value `xs:decimal#1` will instead convert to `xs:decimal` (which potentially retains more precision, but disallows exponential notation), while supplying a function that casts to `union(xs:decimal, xs:double)` will treat the value as `xs:decimal` if there is no exponent, or as `xs:double` otherwise. Supplying the value `fn:identity#1` causes the value to be retained unchanged as an `xs:untypedAtomic`. Before calling the supplied `number-parser`, the value is first checked to ensure that it conforms to the JSON grammar (for example, a leading plus sign and redundant leading zeroes are not allowed); these checks are disabled if the `liberal` option is set to `true`.

The various structures that can occur in JSON are transformed recursively to XDM values as follows:

A JSON object is converted to a map. The entries in the map correspond to the key/value pairs in the JSON object. The key is always of type xs:string; the associated value may be of any type, and is the result of converting the JSON value by recursive application of these rules. For example, the JSON text {"x":2, "y":5} is transformed to the value map{"x":2, "y":5}.

If duplicate keys are encountered in a JSON object, they are handled as determined by the duplicates option defined above.
A JSON array is transformed to an array whose members are the result of converting the corresponding member of the array by recursive application of these rules. For example, the JSON text ["a", "b", null] is transformed (by default) to the value ["a", "b", ()].
A JSON string is converted to an xs:string value. The handling of special characters depends on the escape and fallback options, as described in the table above.
A JSON number is processed using the function supplied in the number-parser option; by default it is converted to an xs:double value using the rules for casting from xs:string to xs:double.
The JSON boolean values true and false are converted to the corresponding xs:boolean values.
The JSON value null is converted to the value given by the null option, which defaults to an empty sequence.

Error Conditions

A dynamic error [err:FOJS0001] occurs if the value of $value does not conform to the JSON grammar, unless the option "liberal":true() is present and the processor chooses to accept the deviation.

A dynamic error [err:FOJS0003] occurs if the option "duplicates":"reject" is present and the value of $value contains a JSON object with duplicate keys.

A dynamic error [err:FOJS0005] occurs if the $options map contains an entry whose key is defined in this specification and whose value is not valid for that key, or if it contains an entry with the key fallback when the option "escape":true() is also present.

Notes

The result of the function will be an instance of one of the following types. An instance of test (or in XQuery, typeswitch) can be used to distinguish them:

map(xs:string, item()?) for a JSON object
array(item()?) for a JSON array
xs:string for a JSON string
xs:double for a JSON number
xs:boolean for a JSON boolean
empty-sequence() for a JSON null (or for empty input)

If the input starts with a byte order mark, this function ignores it. The byte order mark may have been added to the data stream in order to facilitate decoding of an octet stream to a character string, but since this function takes a character string as input, the byte order mark serves no useful purpose.

The possibility of the input containing characters that are not valid in XML (for example, unpaired surrogates) arises only when such characters are expressed using JSON escape sequences. This is the only possibility, because the input to the function is an instance of xs:string, which by definition can contain only those characters that are valid in XML.

Examples

Expression:	`parse-json('{"x":1, "y":[3,4,5]}')`
Result:	map { "x": 1e0, "y": [ 3e0, 4e0, 5e0 ] }
Expression:	`parse-json('"abcd"')`
Result:	"abcd"
Expression:	`parse-json('{"x":"\\", "y":"\u0025"}')`
Result:	map { "x": "\", "y": "%" }
Expression:	parse-json( '{"x":"\\", "y":"\u0025"}', map { 'escape': true() } )
Result:	map { "x": "\\", "y": "%" }
Expression:	parse-json( '{"x":"\\", "y":"\u0000"}' )
Result:	map { "x": "\", "y": char(0xFFFD) }
Expression:	parse-json( '{"x":"\\", "y":"\u0000"}', map { 'escape': true() } )
Result:	map { "x": "\\", "y": "\u0000" }
Expression:	parse-json( '{"x":"\\", "y":"\u0000"}', map { 'fallback': function($s) { '[' \|\| $s \|\| ']' } } )
Result:	map { "x": "\", "y": "[\u0000]" }
Expression:	parse-json( "1984.2", map { 'number-parser': fn { xs:integer(round(.)) } } )
Result:	1984
Expression:	parse-json( '[ 1, -1, 2 ]', map { 'number-parser': fn { boolean(. >= 0) } } )
Result:	[ true(), false(), true() ]
Expression:	parse-json('["a", null, "b"]', map { 'null': xs:QName("fn:null") } )
Result:	[ "a", xs:QName("fn:null"), "b" ]

15.3.4 fn:json-doc

Summary

Reads an external resource containing JSON, and returns the result of parsing the resource as JSON.

Signature

`fn:json-doc`(
`$href`	`as` `xs:string?`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `item()?`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on static base URI.

Rules

If the second argument is omitted or an empty sequence, the result is the same as calling the two-argument form with an empty map as the value of the $options argument.

The effect of the two-argument function call fn:json-doc($H, $M)is equivalent to the function composition fn:unparsed-text($H) => fn:parse-json($M); except that:

The function may accept a resource in any encoding. [RFC 7159] requires UTF-8, UTF-16, or UTF-32 to be accepted, but it is not an error if a different encoding is used. Unless external encoding information is available, the function must assume that the encoding is one of UTF-8, UTF-16, or UTF-32, and must distinguish these cases by examination of the initial octets of the resource.
If the resource contains characters that are not ·permitted characters·, then rather than raising an error as fn:unparsed-text#1 does, the function replaces such characters by the equivalent JSON escape sequence prior to parsing.

Note:

Equivalently, the implementation can use some other internal representation of strings that allows non-XML characters to be manipulated.

If $href is the empty sequence, the function returns the empty sequence.

Error Conditions

The function may raise any error defined for the fn:unparsed-text or fn:parse-json functions.

Notes

If the input cannot be decoded (that is, converted into a sequence of Unicode codepoints, which may or may not represent characters), then a dynamic error occurs as with the fn:unparsed-text function.

If the input can be decoded, then the possibility still arises that the resulting sequence of codepoints includes codepoints that do not represent characters that are valid in the version of XML that the processor supports. Such codepoints are translated into JSON escape sequences (for example, \uFFFF), and the JSON escape sequence is then passed to the fallback function specified in the $options argument, which in turn defaults to a function that returns the Unicode REPLACEMENT CHARACTER (xFFFD).

15.3.5 fn:json-to-xml

Summary

Parses a string supplied in the form of a JSON text, returning the results in the form of an XML document node.

Signature

`fn:json-to-xml`(
`$value`	`as` `xs:string?`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `document-node()?`

Properties

This function is ·nondeterministic·, ·context-dependent·, and ·focus-independent·. It depends on static base URI.

Rules

If the second argument is omitted or an empty sequence, the result is the same as calling the two-argument form with an empty map as the value of the $options argument.

The first argument is a JSON text as defined in [RFC 7159], in the form of a string. The function parses this string to return an XDM node.

If $value is an empty sequence, the function returns the empty sequence.

The $options argument can be used to control the way in which the parsing takes place. The ·option parameter conventions· apply.

The entries that may appear in the $options map are as follows:

Key	Value	Meaning
`liberal`	Determines whether deviations from the syntax of RFC7159 are permitted. Type: `xs:boolean` Default: `false`
	`false`	The input must consist of an optional byte order mark (which is ignored) followed by a string that conforms to the grammar of `JSON-text` in [RFC 7159]. An error must be raised (see below) if the input does not conform to the grammar.
	`true`	The input may contain deviations from the grammar of [RFC 7159], which are handled in an ·implementation-defined· way. (Note: some popular extensions include allowing quotes on keys to be omitted, allowing a comma to appear after the last item in an array, allowing leading zeroes in numbers, and allowing control characters such as tab and newline to be present in unescaped form.) Since the extensions accepted are implementation-defined, an error may be raised (see below) if the input does not conform to the grammar.
`duplicates`	Determines the policy for handling duplicate keys in a JSON object. To determine whether keys are duplicates, they are compared using the Unicode codepoint collation, after expanding escape sequences, unless the `escape` option is set to `true`, in which case keys are compared in escaped form. Type: `xs:string` Default: `If validate is true then reject, otherwise retain.`
	`reject`	An error is raised [err:FOJS0003] if duplicate keys are encountered.
	`use-first`	If duplicate keys are present in a JSON object, all but the first of a set of duplicates are ignored.
	`retain`	If duplicate keys are present in a JSON object, the XML result of the function will also contain duplicates (making it invalid against the schema). This value is therefore incompatible with the option `validate=true` [err:FOJS0005]
`validate`	Determines whether the generated XML tree is schema-validated. Type: `xs:boolean` Default: `Implementation-defined.`
	`true`	Indicates that the resulting XDM instance must be typed; that is, the element and attribute nodes must carry the type annotations that result from validation against the schema given at C.2 Schema for the result of fn:json-to-xml, or against an ·implementation-defined· schema if the `liberal` option has the value `true`.
	`false`	Indicates that the resulting XDM instance must be untyped.
`escape`	Determines whether special characters are represented in the XDM output in backslash-escaped form. Type: `xs:boolean` Default: `false`
	`false`	All characters in the input that are valid in the version of XML supported by the implementation, whether or not they are represented in the input by means of an escape sequence, are represented as unescaped characters in the result. Any characters or codepoints that are not valid XML characters (for example, unpaired surrogates) are passed to the `fallback` function as described below; in the absence of a fallback function, they are replaced by the Unicode `REPLACEMENT CHARACTER` (`xFFFD`). The attributes `escaped` and `escaped-key` will not be present in the XDM output.
	`true`	JSON escape sequences are used in the result to represent special characters in the JSON input, as defined below, whether or not they were represented using JSON escape sequences in the input. The characters that are considered “special” for this purpose are: all codepoints in the range `x00` to `x1F` or `x7F` to `x9F`; all codepoints that do not represent characters that are valid in the version of XML supported by the processor, including codepoints representing unpaired surrogates; the backslash character itself (`x5C`). Such characters are represented using a two-character escape sequence where available (for example, `\t`), or a six-character escape sequence otherwise (for example `\uDEAD`). Characters other than these will not be escaped in the result, even if they were escaped in the input. In the result: Any `string` element whose string value contains a backslash character must have the attribute value `escaped="true"`. Any element that contains a `key` attribute whose string value contains a backslash character must have the attribute `escaped-key="true"`. The values of the `escaped` and `escaped-key` attributes are immaterial when there is no backslash present, and it is never necessary to include either attribute when its value is `false`.
`fallback`	Provides a function which is called when the input contains an escape sequence that represents a character that is not valid in the version of XML supported by the implementation. It is an error to supply the `fallback` option if the `escape` option is present with the value `true`. Type: `(function(xs:string) as xs:anyAtomicType)?` Default: `fn { char(0xFFFD) }`
`fallback`	`User-supplied function`	The function is called when the JSON input contains an escape sequence that is valid according to the JSON grammar, but which does not represent a character that is valid in the version of XML supported by the processor. In the case of surrogates, it is called once for any six-character escape sequence that is not properly paired with another surrogate. The untyped atomic value supplied as the argument will always be a two- or six-character escape sequence, starting with a backslash, that conforms to the rules in the JSON grammar (as extended by the implementation if `liberal:true()` is specified): for example `\b` or `\uFFFF` or `\uDEAD`. By default, the escape sequence is replaced with the Unicode `REPLACEMENT CHARACTER`. The function is not called for an escape sequence that is invalid against the grammar (for example `\x0A`). The string, which results from invoking `fn:string` on the result of the function, is inserted into the result in place of the invalid character. The function also has the option of raising a dynamic error by calling `fn:error`.
`number-parser`	Determines how numeric values should be processed. Type: `(function(xs:untypedAtomic) as item()?)?` Default: `xs:double#1`
`number-parser`	`User-supplied function`	The supplied function is called to process the string value of any JSON number in the input. By default, numbers are processed by converting to `xs:double` using the XPath casting rules. Supplying the value `xs:decimal#1` will instead convert to `xs:decimal` (which potentially retains more precision, but disallows exponential notation), while supplying a function that casts to `union(xs:decimal, xs:double)` will treat the value as `xs:decimal` if there is no exponent, or as `xs:double` otherwise. Supplying the value `fn:identity#1` causes the value to be retained unchanged as an `xs:untypedAtomic`. Before calling the supplied `number-parser`, the value is first checked to ensure that it conforms to the JSON grammar (for example, a leading plus sign and redundant leading zeroes are not allowed); these checks are disabled if the `liberal` option is set to `true`.

The various structures that can occur in JSON are transformed recursively to XDM values according to the rules given in 15.3.2 XML Representation of JSON.

The function returns a document node, whose only child is the element node representing the outermost construct in the JSON text.

The function is ·nondeterministic with respect to node identity·: that is, if the function is called twice with the same arguments, it is ·implementation-dependent· whether the same node is returned on both occasions.

The base URI of the returned document node is taken from the static base URI of the function call.

The choice of namespace prefix (or absence of a prefix) in the names of constructed nodes is ·implementation-dependent·.

The XDM tree returned by the function does not contain any unnecessary (albeit valid) nodes such as whitespace text nodes, comments, or processing instructions. It does not include any whitespace in the value of number or boolean element nodes, or in the value of escaped or escaped-key attribute nodes.

If the result is typed, every element named string will have an attribute named escaped whose value is either true or false, and every element having an attribute named key will also have an attribute named escaped-key whose value is either true or false.

If the result is untyped, the attributes escaped and escaped-key will either be present with the value true, or will be absent. They will never be present with the value false.

Error Conditions

An error is raised [err:FOJS0001] if the value of $value does not conform to the JSON grammar as defined by [RFC 7159], unless the option "liberal":true() is present and the processor chooses to accept the deviation.

An error is raised [err:FOJS0004] if the value of the validate option is true and the processor does not support schema validation or typed data.

An error is raised [err:FOJS0005] if the value of $options includes an entry whose key is defined in this specification, and whose value is not a permitted value for that key.

Notes

To read a JSON file, this function can be used in conjunction with the fn:unparsed-text function.

Many JSON implementations allow commas to be used after the last item in an object or array, although the specification does not permit it. The option spec="liberal" is provided to allow such deviations from the specification to be accepted. Some JSON implementations also allow constructors such as new Date("2000-12-13") to appear as values: specifying spec="liberal" allows such extensions to be accepted, but does not guarantee it. If such extensions are accepted, the resulting value is implementation-defined, and will not necessarily conform to the schema at C.2 Schema for the result of fn:json-to-xml.

The possibility of the input containing characters that are not valid in XML (for example, unpaired surrogates) arises only when such characters are expressed using JSON escape sequences. This is the only possibility because the input to the function is an instance of xs:string, which by definition can contain only those characters that are valid in XML.

Examples

Expression:	json-to-xml( '{"x": 1, "y": [3,4,5]}', map { "validate": false() } )
Result:	<map xmlns="http://www.w3.org/2005/xpath-functions"> <number key="x">1</number> <array key="y"> <number>3</number> <number>4</number> <number>5</number> </array> </map> (with whitespace added for legibility)
Expression:	json-to-xml( '"abcd"', map { 'liberal': false() } )
Result:	<string xmlns="http://www.w3.org/2005/xpath-functions">abcd</string>
Expression:	json-to-xml( '{"x": "\\", "y": "\u0025"}', map { "validate": false() } )
Result:	<map xmlns="http://www.w3.org/2005/xpath-functions"> <string key="x">\</string> <string key="y">%</string> </map> (with whitespace added for legibility)
Expression:	json-to-xml( '{"x": "\\", "y": "\u0025"}', map { 'escape': true(), "validate": false() } )
Result:	<map xmlns="http://www.w3.org/2005/xpath-functions"> <string escaped="true" key="x">\\</string> <string key="y">%</string> </map> (with whitespace added for legibility) (But see the detailed rules for alternative values of the `escaped` attribute on the second `string` element.)
The following example illustrates use of the `fallback` function to handle characters that are invalid in XML.
let $jsonstr := unparsed-text('http://example.com/endpoint'), $options := map { 'liberal': true(), 'fallback': function($char as xs:string) as xs:string { let $c0chars := map { '\u0000':'[NUL]', '\u0001':'[SOH]', '\u0002':'[STX]', ... '\u001E':'[RS]', '\u001F':'[US]' }, $replacement := $c0chars($char) return if (exists($replacement)) then $replacement else error(xs:QName('err:invalid-char'), 'Error: ' \|\| $char \|\| ' is not a C0 control character.') } } return json-to-xml($jsonstr, $options)

15.3.6 fn:xml-to-json

Summary

Converts an XML tree, whose format corresponds to the XML representation of JSON defined in this specification, into a string conforming to the JSON grammar.

Signature

`fn:xml-to-json`(
`$node`	`as` `node()?`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `xs:string?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If the second argument is omitted or an empty sequence, the result is the same as calling the two-argument form with an empty map as the value of the $options argument.

The first argument $node is a node; the subtree rooted at this node will typically be the XML representation of a JSON document as defined in 15.3.2 XML Representation of JSON.

If $node is the empty sequence, the function returns the empty sequence.

The $options argument can be used to control the way in which the conversion takes place. The ·option parameter conventions· apply.

The entries that may appear in the $options map are as follows:

Key	Value	Meaning
`indent`	Determines whether additional whitespace should be added to the output to improve readability. Type: `xs:boolean` Default: `false`
	`false`	The processor must not insert any insignificant whitespace between JSON tokens.
	`true`	The processor may insert whitespace between JSON tokens in order to improve readability. The specification imposes no constraints on how this is done.
`number-formatter`	Determines how numeric values should be formatted. Type: `(function(xs:string) as xs:string)?` Default: `()`
	`User-supplied function`	The supplied function is called to process the string value of all `fn:number` elements in the input. For example, setting the value to `fn:identity#1` causes the value to be output unchanged. There is no requirement that the result should be valid JSON.
	`()`	If no function is supplied, numbers are formatted by converting the string value of the `fn:number` element to an `xs:double`, and then converting the result to a string using the casting rules. Note that this will result in exponential notation being used for values outside the range `1e-6` to `1e+6`. A dynamic error occurs for values such as infinity and `NaN` where the resulting JSON would be invalid.

The node supplied as $node must be one of the following: [err:FOJS0006]

An element node whose name matches the name of a global element declaration in the schema given in C.2 Schema for the result of fn:json-to-xml (“the schema”) and that is valid as defined below:
1. If the type annotation of the element matches the type of the relevant element declaration in the schema (indicating that the element has been validated against the schema), then the element is considered valid.
2. Otherwise, the processor may attempt to validate the element against the schema, in which case it is treated as valid if and only if the outcome of validation is valid.
3. Otherwise (if the processor does not attempt validation using the schema), the processor must ensure that the content of the element, after stripping all attributes (at any depth) in namespaces other than http://www.w3.org/2005/xpath-functions, is such that validation against the schema would have an outcome of valid.
  
  Note:
  
  The process described here is not precisely equivalent to schema validation. For example, schema validation will fail if there is an invalid xsi:type or xsi:nil attribute, whereas this process will ignore such attributes.
An element node E having a key attribute and/or an escaped-key attribute provided that E would satisfy one of the above conditions if the key and/or escaped-key attributes were removed.
A document node having exactly one element child and no text node children, where the element child satisfies one of the conditions above.

Furthermore, $node must satisfy the following constraint (which cannot be conveniently expressed in the schema). Every element M that is a descendant-or-self of $node and has local name map and namespace URI http://www.w3.org/2005/xpath-functions must satisfy the following rule: there must not be two distinct children of M (say C₁ and C₂) such that the normalized key of C₁ is equal to the normalized key of C₂. The normalized key of an element C is as follows:

If C has the attribute value escaped-key="true", then the value of the key attribute of C, with all JSON escape sequences replaced by the corresponding Unicode characters according to the JSON escaping rules.
Otherwise (the escaped-key attribute of C is absent or set to false), the value of the key attribute of C.

Nodes in the input tree are handled by applying the following rules, recursively. In these rules the term “an element named N” means "an element node whose local name is N and whose namespace URI is http://www.w3.org/2005/xpath-functions".

A document node having a single element node child is processed by processing that child.
An element named null results in the output null.
An element $E named boolean results in the output true or false depending on the result of xs:boolean(fn:string($E)).
An element $E named number is processed as follows:
1. If the number-formatter option is present and non-empty, the supplied function is called, with the string value of $E as its argument, and the result is output (whether or not it is valid JSON).
2. Otherwise, the result of the expression xs:string(xs:double(fn:string($E))) is output.
Note:

The default formatting results in exponential format being used for numbers whose absolute value is outside the range 1e-6 to 1e+6; although this is valid according to the JSON specification, some receiving applications may be unable to process it. Possible reasons for using a number-formatter might be:
- To avoid use of exponential notation in the output.
- To avoid loss of precision when the numbers to be output have greater precision than an xs:double.
- To improve the human readability of the output, for example by calling fn:format-number to limit the number of decimal places in the result.
- To avoid errors when dealing with values that JSON cannot handle, such as Infinity and NaN (for example, by emitting these as strings within quotation marks).
An element named string results in the output of the string value of the element, enclosed in quotation marks, with any special characters in the string escaped as described below.
An element named array results in the output of the children of the array element, each processed by applying these rules recursively: the items in the resulting list are enclosed between square brackets, and separated by commas.
An element named map results in the output of a sequence of map entries corresponding to the children of the map element, enclosed between curly braces and separated by commas. Each entry comprises the value of the key attribute of the child element, enclosed in quotation marks and escaped as described below, followed by a colon, followed by the result of processing the child element by applying these rules recursively.
Comments, processing instructions, and whitespace text node children of map and array are ignored.

Strings are escaped as follows:

If the attribute escaped="true" is present for a string value, or escaped-key="true" for a key value, then:
1. any valid JSON escape sequence present in the string is copied unchanged to the output;
2. any invalid JSON escape sequence results in a dynamic error [err:FOJS0007];
3. any unescaped occurrence of quotation mark, backspace, form-feed, newline, carriage return, tab, or solidus is replaced by \", \b, \f, \n, \r, \t, or \/ respectively;
4. any other codepoint in the range 1-31 or 127-159 is replaced by an escape in the form \uHHHH where HHHH is the upper-case hexadecimal representation of the codepoint value.
Otherwise (that is, in the absence of the attribute escaped="true" for a string value, or escaped-key="true" for a key value):
1. any occurrence of backslash is replaced by \\
2. any occurrence of quotation mark, backspace, form-feed, newline, carriage return, or tab is replaced by \", \b, \f, \n, \r, or \t respectively;
3. any other codepoint in the range 1-31 or 127-159 is replaced by an escape in the form \uHHHH where HHHH is the upper-case hexadecimal representation of the codepoint value.

Error Conditions

A dynamic error is raised [err:FOJS0005] if the value of $options includes an entry whose key is defined in this specification, and whose value is not a permitted value for that key.

A dynamic error is raised [err:FOJS0006] if the value of $node is not a document or element node or is not valid according to the schema for the XML representation of JSON, or if a map element has two children whose normalized key values are the same.

A dynamic error is raised [err:FOJS0007] if the value of $node includes a string labeled with escaped="true", or a key labeled with escaped-key="true", where the content of the string or key contains an invalid JSON escape sequence: specifically, where it contains a backslash (\) that is not followed by one of the characters ", \, /, b, f, n, r, t, or u, or where it contains the characters \u not followed by four hexadecimal digits (that is [0-9A-Fa-f]{4}).

Notes

The rule requiring schema validity has a number of consequences, including the following:

The input cannot contain no-namespace attributes, or attributes in the namespace http://www.w3.org/2005/xpath-functions, except where explicitly allowed by the schema. Attributes in other namespaces, however, are ignored.
Nodes that do not affect schema validity, such as comments, processing instructions, namespace nodes, and whitespace text node children of map and array, are ignored.
Numeric values are restricted to those that are valid in JSON: the schema disallows positive and negative infinity and NaN.
Duplicate key values are not permitted. Most cases of duplicate keys are prevented by the rules in the schema; additional cases (where the keys are equal only after expanding JSON escape sequences) are prevented by the prose rules of this function. For example, the key values \n and \u000A are treated as duplicates even though the rules in the schema do not treat them as such.

The rule allowing the top-level element to have a key attribute (which is ignored) allows any element in the output of the fn:json-to-xml function to be processed: for example, it is possible to take a JSON document, convert it to XML, select a subtree based on the value of a key attribute, and then convert this subtree back to JSON, perhaps after a transformation. The rule means that an element with the appropriate name will be accepted if it has been validated against one of the types mapWithinMapType, arrayWithinMapType, stringWithinMapType, numberWithinMapType, booleanWithinMapType, or nullWithinMapType.

Examples

The input `<array xmlns="http://www.w3.org/2005/xpath-functions"><number>1</number><string>is</string><boolean>1</boolean></array>` produces the result `[1,"is",true]`.
The input `<map xmlns="http://www.w3.org/2005/xpath-functions"><number key="Sunday">1</number><number key="Monday">2</number></map>` produces the result `{"Sunday":1,"Monday":2}`.

15.3.7 fn:json

Summary

Creates a JSON representation of an arbitrary XDM value.

Signature

`fn:json`(
`$input`	`as` `xs:string?`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `xs:string`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

This function returns a string, in JSON format, containing a representation of the supplied input $input. The function is error-free (it accepts any input sequence whatsoever), but it is not lossless: there are cases when two different XDM values will have the same JSON representation. For example, the sequence (1, 2) and the array [1, 2] are both output as [1,2].

The entries that may appear in the $options map are as follows:

Key	Value	Meaning
`indent`	Determines whether additional whitespace should be added to the output to improve readability. Type: `xs:boolean` Default: `false`
	`false`	The processor must not insert any insignificant whitespace between JSON tokens.
	`true`	The processor may insert whitespace between JSON tokens in order to improve readability. The specification imposes no constraints on how this is done.
`element-map`	Determines whether elements whose children are element nodes with distinct names should be treated specially. Type: `xs:boolean` Default: `true`
	`false`	The processor treats such elements in the same way as any other element.
	`true`	The processor generates a JSON object in which the child element names are used as JSON property names.

An input sequence is handled as follows:

An empty sequence is output as the JSON value null.
A singleton sequence is output following the rules for processing items, below.
A sequence of two or more items results in a JSON array, whose members are constructed from the items by applying the rules below.

Items are processed as follows:

Atomic values
- An xs:boolean value is output as the JSON value true or false.
- A numeric value, other than INF, -INF, or NaN, is output as a JSON number.
- Any other atomic value is cast to xs:string, and the result is output as a JSON string, escaped as described below.
Nodes
- Document nodes
  
  A document node is output as a JSON object with two properties, in order:
  - A property #document set to the value of the base URI of the document if available, or an empty string otherwise..
  - A property #content whose value follows the rules for outputting the content of an element node, given below.
- Element nodes
  
  An element node is output as a JSON object with the following properties, in order:
  - #element set to the local name of the element.
  - If the element name has a prefix, #prefix, set to the value of the prefix.
  - If the element name is in a namespace, #namespace, set to the value of the namespace URI.
  - For each attribute of the element, in arbitrary order, a property whose name is derived from the attribute name as follows:
    - If the attribute name is in no namespace, then "@" followed by the local name.
    - If the attribute name is in the XML namespace, then "@xml:" followed by the local name.
    - Otherwise "@Q{uri}local" where uri is the namespace URI and local is the local name.
    The property value is the result of atomizing the attribute node and applying the fn:json function to the result. (For untyped attributes, the result will always be a single string.)
  - The children of the element are processed as follows:
    - If there are no children, nothing is output.
    - If the element has a type annotation that is a simple type, or if its content comprises a single text node, then a property #value set to the result of atomizing the element node and applying the fn:json function to the result.
    - If (a) the children consist exclusively of elements and whitespace-only text nodes, and (b) the child element nodes are all in the same namespace, or all in no namespace, and (c) each child element has a local name that is distinct from the local name of any other child, and (d) the element-map option is not present in $options with the value false(), then a property #content whose value is a JSON object having one property for each child element node. The name of this property is the local name of the element, and the value of the property is obtained by applying these rules recursively, except that for an empty element, the value is represented as JSON null.
    - Otherwise, a property #content whose value is an array, with one member for each child node (including whitespace-only text nodes), obtained by applying the fn:json function to that child node.
- Text nodes
  
  A JSON object with a single property #text whose value is the string value of the text node.
- Comment nodes
  
  A JSON object with a single property #comment whose value is the string value of the comment.
- Processing instruction nodes
  
  A JSON object with a two properties (in order): #processing-instruction set to the name of the processing instruction, and #data set to the string value of the processing instruction node.
- Attribute nodes
  
  Attribute nodes that are reached via an element node are output as described under “element nodes”, above.
  
  Free-standing attribute nodes are output as JSON objects with properties #attribute set to the local name of the attribute, #prefix (if non-empty) set to the prefix of the attribute’s name, #namespace (if non-empty) set to the namespace URI, and #value set to the result of atomizing the attribute value and applying the fn:json function to the result.
- Namespace nodes
- Namespace nodes that are reached via an element node result in no output.
- Free-standing namespace nodes are output as JSON objects with properties #namespace set to the namespace prefix ("" for the default namespace) and #uri set to the namespace URI.
Maps

An XDM map is output as a JSON object with one property for each entry in the map.

The property name is derived from the key value by converting the value to a string and applying escaping rules. If the property name thus generated is the same as a previously output property name, then it is made unique by appending "(N)" where N is the smallest positive integer that makes the resulting value unique.

The property value is derived by applying the fn:json function to the value in the map entry.

Note:

Conflicts between property names can arise because the XDM model allows keys of different types, for example the xs:date value 2020-12-31 and the string value "2020-12-31" can co-exist. The map map{xs:duration('PTD'):20, "P1D":30} is converted to the JSON string {"P1D":20,"P1D(1)":30} or {"P1D":30,"P1D(1)":20}, depending on the (unpredictable) order in which the entries in the map are processed.

Note:

Because the order of entries in a map is unpredictable, the order in which the properties are listed in the JSON output is also unpredictable.
Arrays

An XDM array is output as a JSON array. Each member of the XDM array generates one entry in the JSON array, in order, obtained by applying the fn:json function to the XDM array member.
Functions

An XDM function, other than a map or array, is output as a JSON object with the following properties:
- #function, set to the local name of the function if it has a name, or the empty string otherwise.
- #namespace, set to the namespace URI of the function. The property is omitted for an anonymous function.
- #arity, set to the arity of the function as a JSON number.
- #arguments whose value is an array of strings, which identify the names and types of the function arguments, in the format $Q{uri}local as SequenceType: for example ["$x as double", "$y as string"]. Namespace prefixes must not be used: unprefixed element names and variable names are taken to be in no namespace, and unprefixed type names are taken to be in the namespace http://www.w3.org/2001/XMLSchema.
- #result whose value is a string identifying the type of the function result, using the same conventions as for #arguments.
- Optionally at implementer discretion, #implementation whose value is a string representing the function’s implementation in implementation-defined format.
Strings are escaped as follows:
1. Any occurrence of backslash is replaced by \\
2. Any occurrence of quotation mark, backspace, form-feed, newline, carriage return, or tab is replaced by \", \b, \f, \n, \r, or \t respectively;
3. Any other codepoint in the range 1-31 or 127-159 is replaced by an escape in the form \uHHHH where HHHH is the upper-case hexadecimal representation of the codepoint value.

Notes

In the JSON output, names of properties defined in this specification are prefixed with #; names not so prefixed are derived from names appearing in the input.

Namespace information may be lost (specifically, namespaces that are declared but not used are not retained in the output).

The distinction between sequences and arrays is lost.

The distinction between different atomic types is lost, except for the boolean / number / string distinction present in JSON.

In elements whose children are elements with distinct names, whitespace text nodes are lost, and the namespace URIs and prefixes of the child elements are lost.

Examples

Expression	Result
`json(())`	'null'
`json(12)`	'12'
`json((12, "December"))`	'[12,"December"]'
`json(true())`	'true'
`json(map{"a":1,"b":number('NaN'),"c":(1,2,3)})`	'{"a":1,"b":"NaN","c":[1,2,3]}' ((or some permutation thereof)).
`json(<a x="2">banana</a>)`	'{"#element":"a","@x":"2","#value":"banana"}'
`json(<a><b/><c>2</c></a>)`	'{"#element":"a","#content":{"b":null,"c":"2"}}'
`json(<a><b/><b/><c/></a>)`	'{"#name":"a","#content":[{"#name":"b"},{"#name":"b"},{"#name":"c}]}'
`json(<a>A <i>nice</i> one!</a>)`	'{"#name":"a","#content":["A ",{"#name":"i", "#value":"nice"}," one!"]}'

History

Proposed for 4.0; not yet reviewed.

15.3.8 fn:pin

Summary

Adapts a map or array so that retrieval operations retain additional information.

Signature

`fn:pin`(
`$input`	`as` `item()`
) `as` `item()`

Properties

This function is ·nondeterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function creates a deep copy of the supplied map or array, adapted so that navigation within the deep copy returns items that are labeled with additional information about their position within the containing tree structure.

Note:

The formal specification of the function describes it as constructing a deep copy of the entire tree, but a practical implementation is likely to use a lazy evaluation strategy, so the only costs incurred are for items actually selected within the tree.

The function makes use of the concept of labeled items, an extension to the data model described in Section 2.10 Labeled Items^DM40.

The supplied value of $input must be either a map or an array.

The result is as follows:

If $input is a map M, the result is a map M′ derived from M as follows:
1. Any existing label on M is discarded.
2. M′ acquires a label having the property pinned set to the value true, and the property id set to an arbitrary xs:string value that is unique within the execution scope.
3. For every key-value pair (K, V) in M, M′ will have a key-value pair (K, V′) in which the key K is unchanged, and the value V′ is derived from V by applying the function derived-value(M', K, V), defined below.
If $input is an array A, the result is an array A′ derived from A as follows:
1. Any existing label on A is discarded.
2. A′ acquires a label having the property pinned set to the value true, and the property id set to an arbitrary xs:string value that is unique within the execution scope.
3. For every member V in A, whose 1-based index position in A is X, A′ will have a member V′ derived from V by applying the function derived-value(A', X, V), defined below.
The id property described in the previous paragraphs is allocated only to the top-level map or array (the one supplied as an explicit argument to the fn:pin function). The function is not ·deterministic·: that is, if the function is called twice with the same arguments, it is ·implementation-dependent· whether the same id property is allocated on both occasions.
If $input is anything other than a map or an array, a type error is raised.
The function derived-value(P, K, V) has the following logic. For every item J in V, V′ will contain an item J′ that is derived from J as follows:
1. Let TEMP be:
  1. If J is a map or array, then fn:pin(J).
    
    Note:
    
    Note however that the id property of TEMP is not used, so there is no need to generate it.
  2. Otherwise, J.
2. J′ is then a labeled item having the same subject as TEMP, together with a label having the following properties:
  
  pinned
  
  true
  
  key
  
  K
  
  position
  
  The 1-based position of J within V.
  
  parent
  
  P
  
  ancestors
  
  A zero-arity function item delivering the value of (?parent, ?parent!label(.)?ancestors()).
  
  path
  
  A zero-arity function item delivering the value of (?parent!label(.)?path(), ?key).

Notes

The effect of calling pin on a map or array is that subsequent retrieval operations within the pinned map or array return labeled results, whose labels contain useful information about where the results were found. For example, an expression such as json-doc($uri)??name will return the values of all entries in the JSON tree having the key "name"; but very little can be done with this information because the result is simply a sequence of (typically) strings with no context. By contrast, the result of pin(json-doc($uri))??name is the same set of strings, labeled with information about where they were found. For example, if $result is the result of the expression pin(json-doc($uri))??name, then:

$result => label()?parent?ssn locates the map that contained each name, and returns the value of the ssn entry in that map.
$result => label()?ancestors()?course returns the values of any course entries in containing maps.
$result => label()?path() returns a sequence of map keys and array index values representing the location of the found entries within the JSON structure.

Editorial note
The `id` property on the root of a pinned map or array is intended to support deep update operations, which have not yet been defined.

Examples

Expression:	`pin(["a","b","c"])?1 => label()?parent => array:foot()`
Result:	"c"
Expression:	`pin(["a","b","c","d"]) => array:remove(2)?* =!> label()?key`
Result:	1, 3, 4
Expression:	let $data := map{ "fr":map{"capital":"Paris", "languages":["French"]}, "de":map{"capital":"Berlin", "languages":["German"]} } return pin($data)??languages[.='German']!label()?path()[1]
Result:	"de"

History

Proposed for 4.0

15.3.9 fn:label

Summary

Returns the label associated with a labeled item, as a map.

Signature

`fn:label`(
`$input`	`as` `item()?`
) `as` `map(xs:string, item()*)?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $input is an empty sequence, the function returns an empty sequence.

If $input is an item that has no label, the function returns an empty map.

If $input is a labeled item, the function returns the label, as a map.

Notes

The function makes use of the concept of labeled items, an extension to the data model described in Section 2.10 Labeled Items^DM40.

The data model allows any item to be labeled, and allows the label to be any map with string-valued keys. Currently the only operation that creates labeled values is the fn:pin function. For examples illustrating the use of fn:label, see fn:pin.

History

Proposed for 4.0

15.4 Functions on CSV Data

This section describes functions that parse CSV data.

[Definition] The term comma separated values or CSV refers to a wide variety of plain-text tabular data formats with fields and records separated by standard character delimiters (often, but not invariably, commas).

CSV has developed informally for decades, and many variations are found. This specification refers to [RFC 4180], which provides a standardized grammar. This specification defines a mapping from [RFC 4180] to constructs in the XDM model, and provides illustrative examples of how these constructs can be combined with other language features to process CSV data.

A CSV is a 2-dimensional tabular data structure consisting of multiple rows (also known as records). Each row contains multiple fields. Fields occupying the same position in successive rows constitute a column. Columns are identified by position and optionally by name. Column names can be assigned within a CSV using an optional header row.

Function	Meaning
`fn:csv-to-arrays`	Parses CSV data supplied as a string, returning the results in the form of a sequence of arrays of strings.
`fn:parse-csv`	Parses CSV data supplied as a string, returning the results in the form of a `parsed-csv-structure-record` record containing information about the column structure of the data, as well as the data itself as a sequence of `csv-row-record` records.
`fn:csv-to-xml`	Parses CSV data supplied as a string, returning the results as an XML document, as described by 15.4.8 Representing CSV data as XML.

The most basic function for parsing CSV is fn:csv-to-arrays which recognizes the delimiters for rows and fields and returns a sequence of arrays each corresponding to one row. The fields within each array are represented as instances of xs:string.

The other two functions recognize column names, and make it easier to address individual fields using these names. The parse-csv function delivers this capability using XDM maps and functions, while csv-to-xml function represents the information using XDM element nodes.

15.4.1 Common parsing options

All three functions: fn:csv-to-arrays, fn:csv-to-xml, and fn:parse-csv, take options to control parsing, in particular specifying the characters used as delimiters. These core delimiter options are used by the functions that generate CSV data:

`common-csv-options`:
`record(`
`row-delimiter?`	`as` `xs:string`,
`column-delimiter?`	`as` `xs:string`,
`quote-character?`	`as` `xs:string`
`)`

Additionally, the parsing functions share an additional option to control whether leading and trailing whitespace should be stripped or not.

`csv-parsing-options`:
`record(`
`row-delimiter?`	`as` `xs:string`,
`column-delimiter?`	`as` `xs:string`,
`quote-character?`	`as` `xs:string`,
`trim-whitespace?`	`as` `xs:boolean`
`)`

15.4.2 CSV delimiters

The delimiters used for rows, columns, and quoting are configurable. An error is raised if the same delimiter string is used in multiple roles [err:FOCV0003].

15.4.2.1 Row delimiters

Rows in CSV are typically delimited with CRLF (U+000D, U+000A), LF (U+000A), or CR (U+000D) line endings, although field quoting means that there is not always a one-to-one mapping between lines in a file and rows/records in the parsed CSV.

The default row delimiter allows any of CRLF, LF, or CR. Valid values for the row delimiter are a single Unicode character, or one of CRLF, LF, or CR. An error is raised if the row-delimiter option is set to a multi-character string other than CRLF (U+000D, U+000A) [err:FOCV0002].

The last row in the file may or may not be followed by a row delimiter.

15.4.2.2 Column/Field delimiters

Fields in CSV are frequently delimited with a comma. Other field delimiters are useful for example when numeric data uses comma as a decimal separator. The chosen field delimiter is then often a semicolon (U+003B) or tab (U+0009).

The column delimiter defaults to the comma "," (U+002C). The value may be any single Unicode character. An error is raised if the column-delimiter option is set to a multi-character string.

15.4.3 Field quoting

CSVs, as specified in [RFC 4180], require that fields be wrapped with a quote character if they contain either the row or column delimiter. For example:

"A single field, containing a comma","another field containing CRLF
                  within it"

If a field is to contain the quote character, the character must be escaped by doubling it, as with escaping of quotes in XPath string literals (see Section 4.3.1 Literals^XP40). An error is raised [err:FOCV0001] if a quote character appears within a field incorrectly escaped, for example:

incorrectly escaped " quote character

The quotes surrounding quoted fields are not included in the result. The following input string, when parsed, produces a sequence of strings, as shown below:

'"Field 1","Field 2","Field ""with quotes"" 3"'

('Field 1', 'Field 2', 'Field "with quotes" 3')

The quote character defaults to the Unicode quotation mark " (U+0022).

15.4.3.1 Field quoting and column delimiters

No space is allowed between the column delimiter and a quote. An error is raised [err:FOCV0001] if whitespace or other characters occur between a quote character and the nearest column delimiter.

The following example is therefore invalid and parsing it will raise an error.

'"Field 1", "Field 2", "Field 3"'

15.4.4 Basic parsing of CSV to arrays

The result of fn:csv-to-arrays is a sequence of rows, where each row is represented as an array of xs:string values.

The first row of the CSV is returned in the same way as all the other rows. fn:csv-to-arrays does not distinguish between a header row and data rows, and returns all of them.

Example: A CSV with fixed-width rows

For example, given the input:

'Column 1,Column 2,Column 3
Field 1A,Field 1B,Field 1C
Field 2A,Field 2B,Field 2C'

the fn:csv-to-arrays function produces

(
   ["Column 1", "Column 2", "Column 3"],
   ["Field 1A", "Field 1B", "Field 1C"],
   ["Field 2A", "Field 2B", "Field 2C"]
)

Example: A CSV with variable-width rows

It is common practice for all rows in a CSV to have the same number of columns, but this is not required.

'Column 1,Column 2,Column 3
Field 1A,Field 1B,Field 1C
Field 2A,Field 2B,Field 2C,Field 2D'

produces

(
   ["Column 1", "Column 2", "Column 3"],
   ["Field 1A", "Field 1B", "Field 1C"],
   ["Field 2A", "Field 2B", "Field 2C", "Field 2D]
)

[RFC 4180] states that CSVs should contain the same number of fields in each row, so that there are a uniform number of columns. However, the reality is that CSVs can, and sometimes do, contain a variable number of fields in a row. As a result, this function does not truncate or pad the number of fields in each row for any reason. The fn:csv-to-xml and fn:parse-csv functions provide facilities to enforce uniformity and an expected number of columns.

15.4.5 fn:csv-to-arrays

Summary

Parses CSV data supplied as a string, returning the results in the form of a sequence of arrays of strings.

Signature

`fn:csv-to-arrays`(
`$value`	`as` `xs:string?`,
`$options`	`as` `csv-parsing-options`	`:=` `map{}`
) `as` `array(xs:string)*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The $value argument is CSV data, as defined in [RFC 4180], in the form of an xs:string value. The function parses this string. The result of the function is a sequence of arrays of strings, that is array(xs:string)*; each array represents one row of the CSV input.

If $value is the empty sequence, the function returns an empty sequence.

The $options argument can be used to control the way in which the parsing takes place. The ·option parameter conventions· apply.

If the $options argument is omitted or an empty sequence, the result is the same as calling the two-argument form with an empty map as the value of the $options argument.

The entries that may appear in the $options map are as follows:

Key	Value	Meaning
`field-delimiter`	The character used to delimit fields within a record. An instance of `xs:string` whose length is exactly one. Type: `xs:string` Default: `","`
`row-delimiter`	A sequence of strings, any of which can be used to delimit rows within the CSV string. Defaults to CRLF/LF/CR. Type: `xs:string+` Default: `(char(13)\|\|char(10), char(10), char(13))`
`quote-character`	The character used to quote fields within the CSV string. An instance of `xs:string` whose length is exactly one. Type: `xs:string` Default: `'"'`
`trim-whitespace`	Determines whether leading and trailing whitespace is removed from the content of fields. Type: `xs:boolean` Default: `false`
	`false`	Fields will be returned with any leading or trailing whitespace intact.
	`true`	Fields will be returned with leading or trailing whitespace removed, and all other whitespace preserved.

A blank row is represented as an empty array.

An empty field is represented by a zero-length string.

Error Conditions

A dynamic error [err:FOCV0001] occurs if $value does not conform to the [RFC 4180] grammar for quoted fields.

A dynamic error [err:FOCV0002] occurs if the value of the field-delimiter or quote-character option is not a single character.

A dynamic error [err:FOCV0003] occurs if any of the values for field-delimiter, row-delimiter, and quote-character are equal under the Unicode codepoint collation.

Notes

All fields are returned as xs:string values.

Quoted fields in the input are returned without the quotes.

The first row is not treated specially.

For more discussion of the returned data, see 15.4.4 Basic parsing of CSV to arrays.

Examples

Variables
let $lf := char('\n')
let $cr := char('\r')
let $crlf := char('\r')\|\|char('\n')

Handling any of the default record separators:
Expression:	csv-to-arrays(`name,city{$crlf}`\|\| `Bob,Berlin{$crlf}`\|\| `Alice,Aachen{$crlf}`)
Result:	( ["name", "city"], ["Bob", "Berlin"], ["Alice", "Aachen"] )
Expression:	csv-to-arrays(`name,city{$cr}`\|\| `Bob,Berlin{$cr}`\|\| `Alice,Aachen{$cr}`)
Result:	( ["name", "city"], ["Bob", "Berlin"], ["Alice", "Aachen"] )
Expression:	csv-to-arrays(`name,city{$lf}`\|\| `Bob,Berlin{$lf}`\|\| `Alice,Aachen{$lf}`)
Result:	( ["name", "city"], ["Bob", "Berlin"], ["Alice", "Aachen"] )
Quote handling:
Expression:	csv-to-arrays(`"name","city"{$crlf}`\|\| `"Bob","Berlin"{$crlf}`\|\| `"Alice","Aachen"{$crlf}`)
Result:	( ["name", "city"], ["Bob", "Berlin"], ["Alice", "Aachen"] )
Expression:	csv-to-arrays(`"name","city"{$crlf}`\|\| `"Bob ""The Exemplar"" Mustermann","Berlin"{$crlf}`)
Result:	( ["name", "city"], ['Bob "The Exemplar" Mustermann', "Berlin"] )
Non-default record- and field-delimiters:
Expression:	csv-to-arrays("name;city§"\|\| "Bob;Berlin§"\|\| "Alice;Aachen", map{"row-delimiter": "§", "field-delimiter": ";"})
Result:	( ["name", "city"], ["Bob", "Berlin"], ["Alice", "Aachen"] )
Non-default quote character:
Expression:	csv-to-arrays(`\|name\|,\|city\|{$crlf}`\|\| `\|Bob\|,\|Berlin\|{$crlf}`, map{"quote-character": "\|"})
Result:	( ["name", "city"], ["Bob", "Berlin"] )
Trimming whitespace in fields:
Expression:	csv-to-arrays(`name ,city {$crlf}`\|\| `Bob ,Berlin{$crlf}`\|\| `Alice ,Aachen{$crlf}`, map{"trim-whitespace": true()})
Result:	( ["name", "city"], ["Bob", "Berlin"], ["Alice", "Aachen"] )

15.4.6 Enhanced parsing of CSV data to maps and arrays

While fn:csv-to-arrays simply delivers the CSV content as a sequence of arrays, the fn:parse-csv function goes a step further and enables access to the data using column names. The column names may be taken either from the first row of the CSV data, or from data supplied by the caller in the options parameter.

The function returns a parsed-csv-structure-record. This has two parts: columns contains information about the column names, while rows contains the data in the non-header rows:

`parsed-csv-structure-record`:
`record(`
`columns`	`as` `csv-columns-record`,
`rows`	`as` `csv-row-record*`
`)`

15.4.6.1 The `columns` entry

The columns entry describes how the names of columns map to their integer positions. as well as providing the contents of the header row that was used to generate the column names.

`csv-columns-record`:
`record(`
`names`	`as` `map(xs:string, xs:integer)`,
`fields`	`as` `xs:string*`
`)`

If column names were not extracted, then the function returns a csv-columns-record whose names entry is an empty map, and whose fields entry is the empty sequence.

15.4.6.2 The `rows` entry

The rows entry returns the rows themselves. It is a sequence of csv-row records. If the input CSV contains no rows, the function returns a rows entry whose value is the empty sequence.

15.4.6.3 The `csv-row-record`

`csv-row-record`:
`record(`
`fields`	`as` `xs:string*`,
`field`	`as` `function(union(xs:integer, xs:string)) as xs:string?`
`)`

Each csv-row-record represents a single row. The fields entry is a sequence containing the fields as xs:string values.

The field entry contains a function, as described below:

15.4.6.4 The `field` function

The function returned in the field entry is an arity 1 (one) function which takes either a string or an integer as its argument $key, and returns a field from the csv-row-record’s fields sequence by either its 1-based column position (when passed an xs:integer) or column name (when passed an xs:string).

15.4.7 fn:parse-csv

Summary

Parses CSV data supplied as a string, returning the results in the form of a parsed-csv-structure-record record containing information about the column structure of the data, as well as the data itself as a sequence of csv-row-record records.

Signature

`fn:parse-csv`(
`$value`	`as` `xs:string?`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `parsed-csv-structure-record`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The $value argument is CSV data, as defined in [RFC 4180], in the form of a sequence of xs:string values. The function first parses this sequence using fn:csv-to-arrays, and then further processes the result. The initial parsing is exactly as defined for fn:csv-to-arrays, and can be controlled using the same options. Additional options are available to control the way in which header information and column names are handled.

If $value is the empty sequence, the function returns a parsed-csv-structure-record whose rows entry is the empty sequence.

The $options argument can be used to control the way in which the parsing takes place. The ·option parameter conventions· apply.

If the $options argument is omitted or is an empty sequence, the result is the same as calling the two-argument form with an empty map as the value of the $options argument.

The entries that may appear in the $options map are as follows:

Key	Value	Meaning
`field-delimiter`	The character used to delimit fields within a record. An instance of `xs:string` whose length is exactly one. Type: `xs:string` Default: `","`
`row-delimiter`	The sequence of strings used to delimit rows within the CSV string. Defaults to CRLF/LF/CR. Type: `xs:string+` Default: `(" ", " ", " ")`
`quote-character`	The character used to quote fields within the CSV string. An instance of `xs:string` whose length is exactly one. Type: `xs:string` Default: `'"'`
`trim-whitespace`	Determines whether fields should have leading and trailing whitespace removed before being returned. Type: `xs:boolean` Default: `false`
	`false`	Fields will be returned with any leading or trailing whitespace intact. Implementations must preserve whitespace as it occurred in the CSV string.
	`true`	Fields will be returned with leading or trailing whitespace removed, and all non-leading or -trailing whitespace preserved.
`column-names`	Determines whether the first row of the CSV should be treated as a list of column names and returned as a `csv-columns-record` in the `columns` entry of the returned map. Permitted values are a map of type `map(xs:string, xs:integer)` or an `xs:boolean`. Type: `item()` Default: `false`
	`true`	A `csv-columns-record` is constructed using the first row of the CSV data and returned as the `header` entry of the `parsed-csv-structure-record`. The row’s fields are transformed into a map of the form `{ "Column name": column-number }` for the `names` entry of the `csv-columns-record`, and the fields of the row are returned as a sequence of strings (`xs:string*`) for the `fields` entry. The first (header) row is excluded from the `rows` entry of the returned `parsed-csv-structure-record`.
	`false`	The function returns an empty `csv-columns-record`, equivalent to the value `map { "names": map {}, "fields": () }`, in the `columns` entry of the returned `parsed-csv-structure-record`. The first row is not excluded from the `rows` entry of the `parsed-csv-structure-record`.
	`map(xs:string, xs:integer)`	A `csv-columns-record` is constructed using the supplied map and returned as the `header` entry of the `parsed-csv-structure-record`. The supplied map is used as the `names` entry, and a sequence of strings for the `fields` is constructed, filling in blank columns with the empty string, and the fields of the row are returned as the `fields` entry. The first row is not excluded from the `rows` entry of the `parsed-csv-structure-record`.
`filter-columns`	A sequence indicating which fields to return and in which order. If this option is absent or empty, all fields are returned in their original order. Items in the sequence are treated as the index of the column to return. In the returned data, only fields from the specified columns are returned, and in the order specified. This option is mutually exclusive with the `number-of-columns` option. Specifying both options will cause an [err:FOCV0006] error. Type: `xs:integer` Default:* `()`
`number-of-columns`	Specifies how many columns to return. This option is mutually exclusive with the `filter-columns` option. Specifying both options will cause an [err:FOCV0006] error. Type: `union(enum("all", "first-row"), xs:integer)` Default: `"all"`
	`'all'`	All fields from all rows are returned, without being padded or truncated, regardless of whether rows have varying numbers of fields, or of how many fields they have.
	`'first-row'`	The number of fields in the first row is counted, and processing proceeds as if that integer had been supplied as the value for this option.
	`xs:integer`	The number of columns is set to this value. Rows with more fields than the supplied value are truncated by discarding the extra fields, as if calling `fn:subsequence(R, 1, I)`, given the row’s sequence of fields in `R`, and the supplied value in `I`. If a row has fewer fields than the supplied value it is padded by appending empty string values until it contains the specified number of fields.

The result of the function is a parsed-csv-structure-record, a map with string keys containing two entries, columns, and rows.

The entry with key "columns" holds a csv-columns-record record. If column names have been extracted, or supplied, then the record will have a names entry whose value is a map of column-name to column-number, map(xs:string, xs:integer). The record’s fields entry will contains the column names as a sequence of strings, xs:string*, replicating the row they were taken from.

If column names were not extracted or supplied, then the csv-columns-record will contain a names entry whose value is an empty map, and a fields entry whose value is the empty sequence.
The entry with key "rows" holds the records of the CSV as a sequence of row records, csv-row-record*. If there is no data in the CSV, this will be the empty sequence.

Each record in the rows sequence contains a fields entry, containing the row’s fields as a sequence of strings, xs:string*, and a field entry containing an arity-one function. The function takes a string or integer key K as input, and returns the field in fields that corresponds to the position K, if K is an xs:integer, or the position obtained by looking up K in the names map if K is an xs:string.

The properties of this function are as follows:
- name: absent
- parameter names: ($key)
- signature: (union(xs:integer, xs:string)) => xs:string?
- non-local variable bindings: none
- implementation: implementation-dependent
- errors: A dynamic error [err:FOCV0004] occurs if the supplied $key is a string and does not occur in the map of column names.
- rules: The function returns the field in the sequence fields entry of this csv-row-record at the position in the sequence either explicitly provided (when the $key argument is an xs:integer), or looked up from the map of name to position in the names entry of the csv-columns-record of the parsed-csv-structure-record this csv-row-record was returned as part of.
  
  When the argument is a string, if the string is missing from the keys of the names map , then implementations must raise an [err:FOCV0004].
  
  When the argument is an integer, if the integer position is outside the bounds of the sequence contained in the fields entry of this csv-row-record (i.e. is greater than the size of the sequence), then implementations must return the empty string.

If column names were extracted from the first row of the CSV, when there are duplicate column names, implementations must include only the first occurrence in the names entry of the csv-columns-record, ignoring subsequent entries. Any fields in the first record whose value is the empty string must also be omitted.

If the number-of-columns options is set to "first-row" or an integer, or the filter-columns option is set, and the column-names option is set to true(), the filtering of columns is performed before the extraction of the first row and creation of the csv-columns-record.

If the number-of-columns options is set to "first-row" or an integer, or the filter-columns option is set, and the column-names option is set to a map(xs:string, xs:integer), then filtering of columns does not affect the creation of the csv-columns-record, and it is possible that the number of fields in the rows is smaller than the number of fields in the csv-columns-record.

Error Conditions

A dynamic error [err:FOCV0001] occurs if the value of $csv does not conform to the [RFC 4180] grammar for quoted fields.

A dynamic error [err:FOCV0002] occurs if one or more of the values for field-delimiter or quote-character are specified and are not a single character.

A dynamic error [err:FOCV0003] occurs if any of the values for field-delimiter, row-delimiter, quote-character are equal.

A dynamic error [err:FOCV0005] occurs if any column-index integers, such as the values in a map supplied to column-names, or as the value of number-of-columns or filter-columns, are negative or zero.

A dynamic error [err:FOCV0006] occurs if both the number-of-columns and filter-columns options are set in a call to fn:parse-csv.

Notes

All fields are returned as xs:string values.

Quoted fields in the input are returned without the quotes.

For more discussion of the returned data, see 15.4.6 Enhanced parsing of CSV data to maps and arrays.

Examples

Variables
let $crlf := char('\r')\|\|char('\n')
let $csv-string := `name,city{$crlf}`\|\| `Bob,Berlin{$crlf}`\|\| `Alice,Aachen{$crlf}`
let $options := map { "row-delimiter": "§", "field-delimiter": ";", "quote-character": "\|" }
let $non-std-csv := `\|name\|;\|city\|§\|Bob\|;\|Berlin\|§\|Alice\|;\|Aachen\|`
let $csv-string := `Alice,Aachen{$crlf}Bob,Berlin{$crlf}`
let $options := map { "column-names": map { "Person": 1, "Location": 2 } }
let $csv-uneven-cols := concat( `date,name,city,amount,currency,original amount,note{$crlf}`, `2023-07-19,Bob,Berlin,10.00,USD,13.99{$crlf}`, `2023-07-20,Alice,Aachen,15.00{$crlf}`, `2023-07-20,Charlie,Celle,15.00,GBP,11.99,cake,not a lie{$crlf}`)

With defaults for delimiters and quotes, and default column extraction (false):
Expression:	map:keys(parse-csv($csv-string))
Result:	("columns", "rows")
Expression:	parse-csv($csv-string)?columns
Result:	map { "names": map {}, "fields": () }
Expression:	count(parse-csv($csv-string)?rows)
Result:	3
Expression:	parse-csv($csv-string)?rows[1]?field("name")
Result:	Raises error FOCV0004.
Expression:	parse-csv($csv-string)?rows[1]?field(2)
Result:	"city"
With defaults for delimiters and quotes, and `columns: true()` set:
Expression:	parse-csv($csv-string, map {"column-names": true()})?columns
Result:	map { "names": map { "name": 1, "city": 2 }, "fields": ("name", "city") }
Expression:	count(parse-csv($csv-string, map {"column-names": true()})?rows)
Result:	2
Expression:	parse-csv($csv-string, map {"column-names": true()})?rows[1]?fields
Result:	("Bob", "Berlin")
Expression:	parse-csv($csv-string, map {"column-names": true()})?rows[1]?field("name")
Result:	"Bob"
Expression:	parse-csv($csv-string, map {"column-names": true()})?rows[1]?field(2)
Result:	"Berlin"
Non-default record- and field-delimiters, non-default quotes:
Expression:	parse-csv($non-std-csv, $options)?rows[3]?field(1)
Result:	"Alice"
Specifying column names explicitly:
Expression:	map:keys(parse-csv($csv-string, $options))
Result:	("columns", "rows")
Expression:	parse-csv($csv-string, $options)?columns
Result:	map { "names": map { "Person": 1, "Location": 2 }, "fields": ("Person", "Location") }
Expression:	count(parse-csv($csv-string, $options)?rows)
Result:	2
Expression:	parse-csv($csv-string, $options)?rows[1]?field(1)
Result:	"Alice"
Expression:	parse-csv($csv-string, $options)?rows[2]?field("Location")
Result:	"Berlin"
Filtering columns, with `column-names: true()`
Expression:	parse-csv($csv-uneven-cols, map { "column-names": true(), "filter-columns": (2,1,4) }) ?columns?fields
Result:	("name","date","amount")
Expression:	for $r in parse-csv($csv-uneven-cols, map { "column-names": true(), "filter-columns": (2,1,4) })?rows return array { $r?fields }
Result:	( ["Bob","2023-07-19","10.00"], ["Alice","2023-07-20","15.00"], ["Charlie","2023-07-20","15.00"] )
Filtering columns, with `column-names: map { ... }`
Expression:	parse-csv($csv-uneven-cols, map { "column-names": map { "Person": 1, "Amount": 3 }, "filter-columns": (2,1,4) }) ?columns
Result:	map { "names": map { "Person": 1, "Amount": 3 }, "fields": ("Person", "", "Amount") }
Specifying the number of columns using `"first-row"` and `column-names: false()`
Expression:	for $r in parse-csv($csv-uneven-cols, map { "number-of-columns": "first-row" })?rows return array { $r?fields }
Result:	( ["date","name","city","amount","currency","original amount","note"], ["2023-07-19","Bob","Berlin","10.00","USD","13.99",""], ["2023-07-20","Alice","Aachen","15.00","","",""], ["2023-07-20","Charlie","Celle","15.00","GBP","11.99","cake"] )
Specifying the number of columns with a number and `column-names: true()`
Expression:	parse-csv($csv-uneven-cols, map { "column-names": true(), "number-of-columns": 6 }) ?columns?fields
Result:	map { "names": map { "date": 1, "name": 2, "city": 3, "amount": 4, "currency": 5, "original amount": 6 }, "fields": ("date", "name", "city", "amount", "currency", "original amount") }
Expression:	for $r in parse-csv($csv-uneven-cols, map { "column-names": true(), "number-of-columns": 6 })?rows return array { $r?fields }
Result:	( ["2023-07-19","Bob","Berlin","10.00","USD","13.99"], ["2023-07-20","Alice","Aachen","15.00","",""], ["2023-07-20","Charlie","Celle","15.00","GBP","11.99"] )

15.4.8 Representing CSV data as XML

The fn:csv-to-xml function returns an XDM node tree representing the CSV data. Following is a CSV text and the XML serialization of the corresponding node tree.

Name,Date,Amount
Alice,2023-07-14,1.23
Bob,2023-07-14,2.34

<csv xmlns="http://www.w3.org/2005/xpath-functions">
   <columns>
      <column>Name</column>
      <column>Date</column>
      <column>Amount</column>
   </columns>
   <rows>
      <row>
         <field column="Name">Alice</field>
         <field column="Date">2023-07-14</field>
         <field column="Amount">1.23</field>
      </row>
      <row>
         <field column="Name">Bob</field>
         <field column="Date">2023-07-14</field>
         <field column="Amount">2.34</field>
      </row>
   </rows>
</csv>

If column names were not extracted, then implementations should not include the <header> element, and <field> elements should not have the column attribute:

<csv xmlns="http://www.w3.org/2005/xpath-functions">
   <rows>
      <row>
         <field>Name</field>
         <field>Date</field>
         <field>Amount</field>
      </row>
      <row>
         <field>Alice</field>
         <field>2023-07-14</field>
         <field>1.23</field>
      </row>
      <row>
         <field>Bob</field>
         <field>2023-07-14</field>
         <field>2.34</field>
      </row>
   </rows>
</csv>

An XSD 1.0 schema for the XML representation is provided in C.3 Schema for the result of fn:csv-to-xml.

15.4.9 fn:csv-to-xml

Summary

Parses CSV data supplied as a string, returning the results as an XML document, as described by 15.4.8 Representing CSV data as XML.

Signature

`fn:csv-to-xml`(
`$value`	`as` `xs:string?`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `element(fn:csv)`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on static base URI.

Rules

The arguments have the same meaning, and are subject to the same constraints, as the arguments of fn:parse-csv.

The effect of the function is equivalent to the result of the following XQuery expression (where $options is an empty map if the argument is not supplied):

let $parsedCSV := parse-csv($value, $options)
let $colNames := $parsedCSV?columns?fields
return
   <csv xmlns="http://www.w3.org/2005/xpath-functions"> {
       if (exists($colNames)) {
         <columns> {$colNames ! <column>{.}</column>} </columns>
       },
       <rows> {
         for $row in $parsedCSV?rows?row return
         <row> {
           for member $field at $col in $row return
           <field> {
             if (exists($colnames[$col])) {
               attribute column {$colnames[$col]}
             },
             $field
           } </field>
         } </row>
       } </rows> 
   } </csv>

The namespace prefix used in the names of elements (or its absence) is ·implementation-dependent·.

The base URI of the element nodes in the result is ·implementation-dependent·.

A schema is defined for the structure of the returned element: see C.3 Schema for the result of fn:csv-to-xml.

Error Conditions

See fn:parse-csv.

Examples

Variables

let $crlf := char('\r')||char('\n')

let $csv-string := `name,city{$crlf}Bob,Berlin{$crlf}Alice,Aachen{$crlf}`

let $csv-uneven-cols := concat(
`date,name,city,amount,currency,original amount,note{$crlf}`,
`2023-07-19,Bob,Berlin,10.00,USD,13.99{$crlf}`,
`2023-07-20,Alice,Aachen,15.00{$crlf}`,
`2023-07-20,Charlie,Celle,15.00,GBP,11.99,cake,not a lie{$crlf}`)

An empty CSV with default column extraction (false):
Expression:	csv-to-xml("")
Result:	<csv xmlns="http://www.w3.org/2005/xpath-functions"> <rows/> </csv>
An empty CSV with column extraction:
Expression:	csv-to-xml("", map { "column-names": true() })
Result:	<csv xmlns="http://www.w3.org/2005/xpath-functions"> <columns/> <rows/> </csv>
An empty CSV with explicit column names:
Expression:	csv-to-xml("", map { "column-names": map { "name": 1, "city": 3 } })
Result:	<csv xmlns="http://www.w3.org/2005/xpath-functions"> <columns> <column>name</column> <column/> <column>city</column> </columns> <rows/> </csv>
With defaults for delimiters and quotes, and column extraction:
Expression:	csv-to-xml($csv-string, map { "column-names": true() })
Result:	<csv xmlns="http://www.w3.org/2005/xpath-functions"> <columns> <column>name</column> <column>city</column> </columns> <rows> <row> <field column="name">Bob</field> <field column="city">Berlin</field> </row> <row> <field column="name">Alice</field> <field column="city">Aachen</field> </row> </rows> </csv>
With defaults for delimiters and quotes, and column extraction:
Expression:	csv-to-xml($csv-string, map { "column-names": true() })
Result:	<csv xmlns="http://www.w3.org/2005/xpath-functions"> <columns> <column>name</column> <column>city</column> </columns> <rows> <row> <field column="name">Bob</field> <field column="city">Berlin</field> </row> <row> <field column="name">Alice</field> <field column="city">Aachen</field> </row> </rows> </csv>
Filtering columns
Expression:	csv-to-xml($csv-uneven-cols, map { "column-names": true(), "filter-columns": (2,1,4) })
Result:	<csv xmlns="http://www.w3.org/2005/xpath-functions"> <columns> <column>name</column> <column>date</column> <column>amount</column> </columns> <rows> <row> <field column="name">Bob</field> <field column="date">2023-07-19</field> <field column="amount">10.00</field> </row> <row> <field column="name">Alice</field> <field column="date">2023-07-20</field> <field column="amount">15.00</field> </row> <row> <field column="name">Charlie</field> <field column="date">2023-07-20</field> <field column="amount">15.00</field> </row> </rows> </csv>
Specifying the number of columns, using "all" (the default)
Expression:	csv-to-xml($csv-uneven-cols, map { "column-names": true(), "number-of-columns": "all" })
Result:	<csv xmlns="http://www.w3.org/2005/xpath-functions"> <columns> <column>date</column> <column>name</column> <column>city</column> <column>amount</column> <column>currency</column> <column>original amount</column> <column>note</column> </columns> <rows> <row> <field column="date">2023-07-19</field> <field column="name">Bob</field> <field column="city">Berlin</field> <field column="amount">10.00</field> <field column="currency">USD</field> <field column="original amount">13.99</field> </row> <row> <field column="date">2023-07-20</field> <field column="name">Alice</field> <field column="city">Aachen</field> <field column="amount">15.00</field> </row> <row> <field column="date">2023-07-20</field> <field column="name">Charlie</field> <field column="city">Celle</field> <field column="amount">15.00</field> <field column="currency">GBP</field> <field column="original amount">11.99</field> <field column="note">cake</field> <field>not a lie</field> </row> </rows> </csv>
Specifying the number of columns using `"first-row"`
Expression:	csv-to-xml($csv-uneven-cols, map { "column-names": true(), "number-of-columns": "first-row" })
Result:	<csv xmlns="http://www.w3.org/2005/xpath-functions"> <columns> <column>date</column> <column>name</column> <column>city</column> <column>amount</column> <column>currency</column> <column>original amount</column> <column>note</column> </columns> <rows> <row> <field column="date">2023-07-19</field> <field column="name">Bob</field> <field column="city">Berlin</field> <field column="amount">10.00</field> <field column="currency">USD</field> <field column="original amount">13.99</field> <field column="note"/> </row> <row> <field column="date">2023-07-20</field> <field column="name">Alice</field> <field column="city">Aachen</field> <field column="amount">15.00</field> <field column="currency"/> <field column="original amount"/> <field column="note"/> </row> <row> <field column="date">2023-07-20</field> <field column="name">Charlie</field> <field column="city">Celle</field> <field column="amount">15.00</field> <field column="currency">GBP</field> <field column="original amount">11.99</field> <field column="note">cake</field> </row> </rows> </csv>
Specifying the number of columns with a number
Expression:	csv-to-xml($csv-uneven-cols, map { "column-names": true(), "number-of-columns": 6 })
Result:	<csv xmlns="http://www.w3.org/2005/xpath-functions"> <columns> <column>date</column> <column>name</column> <column>city</column> <column>amount</column> <column>currency</column> <column>original amount</column> </columns> <rows> <row> <field column="date">2023-07-19</field> <field column="name">Bob</field> <field column="city">Berlin</field> <field column="amount">10.00</field> <field column="currency">USD</field> <field column="original amount">13.99</field> </row> <row> <field column="date">2023-07-20</field> <field column="name">Alice</field> <field column="city">Aachen</field> <field column="amount">15.00</field> <field column="currency"/> <field column="original amount"/> </row> <row> <field column="date">2023-07-20</field> <field column="name">Charlie</field> <field column="city">Celle</field> <field column="amount">15.00</field> <field column="currency">GBP</field> <field column="original amount">11.99</field> </row> </rows> </csv>

15.4.10 Illustrative examples of processing CSV data

The following examples illustrate more complex applications making use of CSV parsing functions.

A variable $crlf is assumed to be in scope representing the CRLF string:

let $crlf := fn:char(0x0D)||fn:char(0x0A)

Example: Converting a CSV into an HTML-style table using fn:parse-csv

Direct conversion is a matter of iterating across the records and fields to generate <tr> and <td> elements.

Using XQuery:

let $csv := fn:parse-csv(`name,city{$crlf}Bob,Berlin`)
return <table>
   <thead>{
      for $column in $csv?columns?fields
         return <th>{ $column }</th>
   }</thead>
   <tbody>{
      for $row in $csv?rows return <tr>
         { for $field in $row?fields return <td>{ $field }</td> }
      </tr>
   }</tbody>
</table>

Using XSLT:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:eg="http://example.org/eg"
  xmlns:array="http://www.w3.org/2005/xpath-functions/array"
  exclude-result-prefixes="eg array"
  version="4.0">
  <xsl:output method="xml" indent="true"/>

  <xsl:template match="." mode="csv-th" expand-text="true">
    <th>{.}</th>
  </xsl:template>

  <xsl:template match="." mode="csv-td" expand-text="true">
    <td>{.}</td>
  </xsl:template>

  <xsl:template match="." mode="csv-tr">
    <tr>
      <xsl:apply-templates select=".?fields" mode="csv-td"/>
    </tr>
  </xsl:function>

  <xsl:template name="xsl:initial-template">
    <xsl:variable name="csv" select="parse-csv(`name,city{$crlf}Bob,Berlin`)"/>
    <table>
      <thead>
        <tr>
          <xsl:apply-templates select="$csv?columns?fields" mode="csv-th"/>
        </tr>
      </thead>
      <tbody>
        <xsl:apply-templates select="$csv?rows" mode="csv-tr"/>
      </tbody>
    </table>
  </xsl:template>
</xsl:stylesheet>

Example: Converting a CSV into an HTML-style table using fn:csv-to-xml

The fn:csv-to-xml function makes these kinds of conversion-to-XML-table tasks simpler by providing a simple XML represenation of the data. Here, in XQuery:

let $csv := fn:csv-to-xml(`name,city{$crlf}Bob,Berlin`)
return <table>
   <thead>{
      for $column in $csv/csv/columns/column
         return <th>{ $column }</th>
   }</thead>
   <tbody>{
      for $row in $csv/csv/rows/row
         return <tr>{ for $field in $row/field return <td>{ $field }</td> }</tr>
      }
   }</tbody>
</table>

And in XSLT:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:fn="http://www.w3.org/2005/xpath-functions"
  exclude-result-prefixes="fn"
  version="4.0">
  <xsl:output method="xml" indent="true"/>

  <xsl:template match="fn:column" expand-text="true">
    <th>{.}</th>
  </xsl:template>

  <xsl:template match="fn:field" expand-text="true">
    <td>{.}</td>
  </xsl:template>

  <xsl:template match="fn:row">
    <tr>
      <xsl:apply-templates/>
    </tr>
  </xsl:function>

  <xsl:template match="fn:columns">
    <thead>
      <tr>
        <xsl:apply-templates/>
      </tr>
    </thead>
  </xsl:function>

  <xsl:template match="fn:rows">
    <tbody>
      <xsl:apply-templates/>
    </tbody>
  </xsl:function>

  <xsl:template match="fn:csv">
    <table>
      <xsl:apply-templates/>
    </table>
  </xsl:template>

  <xsl:template name="xsl:initial-template">
    <xsl:apply-templates select="fn:csv-to-xml(`name,city{$crlf}Bob,Berlin`)"/>
  </xsl:template>
</xsl:stylesheet>

15.5 Functions on Invisible XML

This section describes functions that support [Invisible XML] parsing.

Invisible XML defines a BNF-like language for specifying grammars, together with a mapping from sentences in that grammar to an XML representation. By defining an Invisible XML grammar, a great variety of non-XML data formats can be manipulated as if they were XML. The function fn:invisible-xml takes a grammar as input, and returns a function which can be used for parsing data instances and converting them to XML node trees.

15.5.1 fn:invisible-xml

Summary

Creates an Invisible XML parser for a grammar.

Signature

`fn:invisible-xml`(
`$grammar`	`as` `item()?`	`:=` `()`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `function(xs:string) as item()`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Conceptually, an [Invisible XML] processor takes two arguments: a grammar and an input string. The grammar is a description of some format and the parser will attempt to interpret the input string according to that description. The parser returns an XML representation of the input string as parsed by the provided grammar. If parsing fails, it returns an XML representation that indicates an error occurred and may provide additional error information.

For example, the following grammar describes a date as consisting of a year, a month, and a day. Each are a sequence of digits and they are separated by hyphens:

 date = year, -'-', month, -'-', day .
 year = d, d, d, d .
month = '0', d | '1', ['0'|'1'|'2'] .
  day = ['0'|'1'|'2'], d | '3', ['0'|'1'] .
   -d = ['0'-'9'] .

Using this grammar to parse “2023-10-31” will produce:

<date><year>2023</year><month>10</month><day>31</day></date>

Using this grammar to parse “2023-10-32” will produce something like this:

<fail xmlns:ixml='http://invisiblexml.org/NS' ixml:state='failed'>
   <line>1</line>
   <column>10</column>
   <pos>9</pos>
   <unexpected>3</unexpected>
   <permitted>'3', ['0'; '1'; '2']</permitted>
</fail>

The exact format of the error output will vary between implementations. The only required part of the output is the ixml:state attribute that contains the value failed.

Note:

Careful readers will observe that the example grammar will parse “2023-00-00” as a date. The grammar could easily be extended to exclude the “00” forms for month and day, but this is only intended to be an illustrative example.

The fn:invisible-xml function takes a grammar and returns a function that can be used to parse input strings. In practice, constructing a parser from a grammar may be an expensive operation. Returning a parsing function makes it easy to efficiently reuse a parser.

The following options are available:

Key	Meaning
`fail-on-error`	Raise an error if the parse function fails Type: `xs:boolean` Default: `false`

Additional, ·implementation-defined· options may be available, for example, to control aspects of the XML serialization, to specify the grammar start symbol, or to produce output formats other than XML.

If $grammar is the empty sequence, a parser is returned for the Invisible XML specification grammar. If $grammar is not empty, it must be a valid Invisible XML grammar. If it is not, fn:invisible-xml raises err:FOIX0001.

If the fail-on-error option is true(), the parsing function will raise err:FOIX0002 if the input provided cannot be parsed successfully. Otherwise, it returns an XML representation of the error as described by the [Invisible XML] specification.

Examples

Expression:	invisible-xml("S=A. A='a'.")("a")
Result:	<S><A>a</A></S>
Expression:	let $parser := invisible-xml("S=A. A='a'.") let $result := $parser("b") return $result//@:state = 'failed'
Result:	true() (The returned document contains information about the error in the parsed string.)
Expression:	let $parser := invisible-xml("S=A. A='a'.", map { "fail-on-error": true() }) let $result := $parser("b") return $result
Result:	Raises error FOIX0002.

History

Proposed for 4.0

16 Context functions

The following functions are defined to obtain information from the static or dynamic context.

Function	Meaning
`fn:position`	Returns the context position from the dynamic context.
`fn:last`	Returns the context size from the dynamic context.
`fn:current-dateTime`	Returns the current date and time (with timezone).
`fn:current-date`	Returns the current date.
`fn:current-time`	Returns the current time.
`fn:implicit-timezone`	Returns the value of the implicit timezone property from the dynamic context.
`fn:default-collation`	Returns the value of the default collation property from the dynamic context.
`fn:default-language`	Returns the value of the default language property from the dynamic context.
`fn:static-base-uri`	This function returns the value of the executable base URI property from the dynamic context.

16.1 fn:position

Summary

Returns the context position from the dynamic context.

Signature

fn:position() as xs:integer

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

Rules

Returns the context position from the dynamic context. (See Section C.2 Dynamic Context Components ^XP31.)

Error Conditions

A type error is raised [err:XPDY0002]^XP if the context value is absent^DM40.

16.2 fn:last

Summary

Returns the context size from the dynamic context.

Signature

fn:last() as xs:integer

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

Rules

Returns the context size from the dynamic context. (See Section C.2 Dynamic Context Components ^XP31.)

Error Conditions

A type error is raised [err:XPDY0002]^XP if the context size is absent^DM40.

Notes

Under most circumstances, the context size is absent only if the context value is absent. However, XSLT 3.0 with streaming defines situations in which the context value and context position are known, but the context size is unknown.

Examples

Expression	Result
`(1 to 20)[last() - 1]`	19

16.3 fn:current-dateTime

Summary

Returns the current date and time (with timezone).

Signature

fn:current-dateTime() as xs:dateTimeStamp

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

Returns the current dateTime (with timezone) from the dynamic context. (See Section C.2 Dynamic Context Components ^XP31.) This is an xs:dateTime that is current at some time during the evaluation of a query or transformation in which fn:current-dateTime is executed.

This function is ·deterministic·. The precise instant during the query or transformation represented by the value of fn:current-dateTime() is ·implementation-dependent·.

If the implementation supports data types from XSD 1.1 then the returned value will be an instance of xs:dateTimeStamp. Otherwise, the only guarantees are that it will be an instance of xs:dateTime and will have a timezone component.

Notes

The returned xs:dateTime will always have an associated timezone, which will always be the same as the implicit timezone in the dynamic context

Examples

fn:current-dateTime() returns an xs:dateTimeStamp corresponding to the current date and time. For example, a call of fn:current-dateTime() might return 2004-05-12T18:17:15.125Z corresponding to the current time on May 12, 2004 in timezone Z.

16.4 fn:current-date

Summary

Returns the current date.

Signature

fn:current-date() as xs:date

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

Returns xs:date(fn:current-dateTime()). This is an xs:date (with timezone) that is current at some time during the evaluation of a query or transformation in which fn:current-date is executed.

This function is ·deterministic·. The precise instant during the query or transformation represented by the value of fn:current-date is ·implementation-dependent·.

Notes

The returned date will always have an associated timezone, which will always be the same as the implicit timezone in the dynamic context

Examples

fn:current-date() returns an xs:date corresponding to the current date. For example, a call of fn:current-date() might return 2004-05-12+01:00.

16.5 fn:current-time

Summary

Returns the current time.

Signature

fn:current-time() as xs:time

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

Returns xs:time(fn:current-dateTime()). This is an xs:time (with timezone) that is current at some time during the evaluation of a query or transformation in which fn:current-time is executed.

This function is ·deterministic·. The precise instant during the query or transformation represented by the value of fn:current-time() is ·implementation-dependent·.

Notes

The returned time will always have an associated timezone, which will always be the same as the implicit timezone in the dynamic context

Examples

fn:current-time() returns an xs:time corresponding to the current time. For example, a call of fn:current-time() might return 23:17:00.000-05:00.

16.6 fn:implicit-timezone

Summary

Returns the value of the implicit timezone property from the dynamic context.

Signature

fn:implicit-timezone() as xs:dayTimeDuration

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on implicit timezone.

Rules

Returns the value of the implicit timezone property from the dynamic context. Components of the dynamic context are described in Section C.2 Dynamic Context Components ^XP31.

16.7 fn:default-collation

Summary

Returns the value of the default collation property from the dynamic context.

Signature

fn:default-collation() as xs:string

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

Rules

Returns the value of the default collation property from the dynamic context context. Components of the dynamic context are described in [TITLE OF XP31 SPEC, TITLE OF id-xp-dynamic-context-components SECTION]^XP31.

Notes

The default collation property can never be absent. If it is not explicitly defined, a system defined default can be invoked. If this is not provided, the Unicode codepoint collation (http://www.w3.org/2005/xpath-functions/collation/codepoint) is used.

In most cases, the default collation is known statically, and a call on this function can therefore be pre-evaluated during static analysis. The only notable exception is when a call on default-collation() is used to define the default value of a parameter to a user-defined function. In this case it is interpreted as a reference to the default collation in the context of the relevant function call, which may differ from the default collation of the function definition.

16.8 fn:default-language

Summary

Returns the value of the default language property from the dynamic context.

Signature

fn:default-language() as xs:language

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on default language.

Rules

Returns the value of the default language property from the dynamic context. Components of the dynamic context are described in Section 2.1.2 Dynamic Context ^XP31.

Notes

The default language property can never be absent. The functions fn:format-integer, fn:format-date, fn:format-time, and fn:format-dateTime are defined to use the default language if no explicit language is supplied. The default language may play a role in selection of a default collation, but this is not a requirement.

16.9 fn:static-base-uri

Summary

This function returns the value of the executable base URI property from the dynamic context.

Signature

fn:static-base-uri() as xs:anyURI?

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on static base URI.

Rules

The function (despite its name) returns the value of the executable base URI property from the dynamic context. If the property is absent, the empty sequence is returned.

Components of the dynamic context are described in [TITLE OF XP31 SPEC, TITLE OF dynamic_context SECTION]^XP31 .

Notes

The executable base URI will in many cases be the same as the static base URI in the static context. However, XQuery and XSLT give an implementation freedom to use different base URIs during the static analysis phase and the dynamic evaluation phase, that is, for retrieval of compile-time and run-time resources respectively. This is appropriate when the implementation allows the output of static analysis (a “compiled” query or stylesheet) to be deployed for execution to a different location from the one where static analysis took place. In this situation, the fn:static-base-uri function should return a URI suitable for locating resources needed during dynamic evaluation.

If a call on the fn:static-base-uri function appears within the expression used to define the value of an optional parameter to a user-defined function, then the value supplied to the function (if the argument is omitted) will be the executable base URI from the dynamic context of the function caller. This allows such a function to resolve relative URIs supplied in other parameters to the same function.

17 Higher-order functions

17.1 Functions on functions

The functions included in this section operate on function items, that is, values referring to a function.

[Definition] Functions that accept functions among their arguments, or that return functions in their result, are described in this specification as higher-order functions. Some host languages may exclude higher-order functions from the set of functions that they support, or may include such functions in an optional conformance feature.

Note:

Some functions such as fn:parse-json allow the option of supplying a callback function for example to define exception behavior. Where this is not essential to the use of the function, the function has not been classified as higher-order for this purpose; in applications where function items cannot be created, these particular options will not be available.

Function	Meaning
`fn:function-lookup`	Returns a function item having a given name and arity, if there is one.
`fn:function-name`	Returns the name of the function identified by a function item.
`fn:function-arity`	Returns the arity of the function identified by a function item.
`fn:function-annotations`	Returns the annotations of the function identified by a function item.

17.1.1 fn:function-lookup

Summary

Returns a function item having a given name and arity, if there is one.

Signature

`fn:function-lookup`(
`$name`	`as` `xs:QName`,
`$arity`	`as` `xs:integer`
) `as` `function(*)?`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

Rules

A call to fn:function-lookup starts by looking for a function definition^XP40 in the named functions component of the dynamic context (specifically, the dynamic context of the call to fn:function-lookup), using the expanded QName supplied as $name and the arity supplied as $arity. There can be at most one such function definition.

If no function definition can be identified (by name and arity), then an empty sequence is returned.

If a function definition is identified, then a function item is obtained from the function definition using the same rules as for evaluation of a named function reference (see Section 4.6.2.4 Named Function References^XP40). The captured context of the returned function item (if it is context dependent) is the static and dynamic context of the call on fn:function-lookup.

If the arguments to fn:function-lookup identify a function that is present in the static context of the function call, the function will always return the same function that a static reference to this function would bind to. If there is no such function in the static context, then the results depend on what is present in the dynamic context, which is ·implementation-defined·.

Error Conditions

An error is raised if the identified function depends on components of the static or dynamic context that are not present, or that have unsuitable values. For example [err:XPDY0002]^XP is raised for the call function-lookup(xs:QName("fn:name"), 0) if the context value is absent, and [err:FODC0001] is raised for the call function-lookup(xs:QName("fn:id"), 1) if the context value is not a single node in a tree that is rooted at a document node. The error that is raised is the same as the error that would be raised by the corresponding function if called with the same static and dynamic context.

Notes

This function can be useful where there is a need to make a dynamic decision on which of several statically known functions to call. It can thus be used as a substitute for polymorphism, in the case where the application has been designed so several functions implement the same interface.

The function can also be useful in cases where a query or stylesheet module is written to work with alternative versions of a library module. In such cases the author of the main module might wish to test whether an imported library module contains or does not contain a particular function, and to call a function in that module only if it is available in the version that was imported. A static call would cause a static error if the function is not available, whereas getting the function using fn:function-lookup allows the caller to take fallback action in this situation.

If the function that is retrieved by fn:function-lookup is ·context-dependent·, that is, if it has dependencies on the static or dynamic context of its caller, the context that applies is the static and/or dynamic context of the call to the fn:function-lookup function itself. The context thus effectively forms part of the closure of the returned function. In practice this applies only where the target of fn:function-lookup is a built-in function, because user-defined functions never depend on the static or dynamic context of the function call. The rule applies recursively, since fn:function-lookup is itself a context-dependent built-in function.

However, the static and dynamic context of the call to fn:function-lookup may play a role even when the selected function definition is not itself context dependent, if the expressions used to establish default parameter values are context dependent.

The function identity is determined in the same way as for a named function reference. Specifically, if there is no context dependency, two calls on fn:function-lookup with the same name and arity must return the same function.

These specifications do not define any circumstances in which the dynamic context will contain functions that are not present in the static context, but neither do they rule this out. For example an API may provide the ability to add functions to the dynamic context. Equally, these specifications do not define any mechanism for creating context-dependent functions other than the built-in context-dependent functions, but neither do they rule out the existence of such functions.

The mere fact that a function exists and has a name does not of itself mean that the function is present in the dynamic context. For example, functions obtained through use of the fn:load-xquery-module function are not added to the dynamic context.

Examples

Expression:	`function-lookup(xs:QName('fn:substring'), 2)('abcd', 2)`
Result:	'bcd'
The expression `(fn:function-lookup(xs:QName('xs:dateTimeStamp'), 1), xs:dateTime#1)[1] ('2011-11-11T11:11:11Z')` returns an `xs:dateTime` value set to the specified date, time, and timezone; if the implementation supports XSD 1.1 then the result will be an instance of the derived type `xs:dateTimeStamp`. The query is written to ensure that no failure occurs when the implementation does not recognize the type `xs:dateTimeStamp`.
The expression let $f := function-lookup(xs:QName('zip:binary-entry'), 2) return if (exists($f)) then $f($href, $entry) else () returns the result of calling `zip:binary-entry($href, $entry)` if the function is available, or an empty sequence otherwise.

17.1.2 fn:function-name

Summary

Returns the name of the function identified by a function item.

Signature

`fn:function-name`(
`$function`	`as` `function(*)`
) `as` `xs:QName?`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If $function refers to a named function, fn:function-name($func) returns the name of that function.

Otherwise ($function refers to an anonymous function), fn:function-name($function) returns an empty sequence.

The prefix part of the returned QName is ·implementation-dependent·.

Examples

Expression	Result
`function-name(substring#2)`	QName("http://www.w3.org/2005/xpath-functions", "fn:substring") (The namespace prefix of the returned QName is not predictable.)
`function-name(function($node) { count($node/*) })`	()

17.1.3 fn:function-arity

Summary

Returns the arity of the function identified by a function item.

Signature

`fn:function-arity`(
`$function`	`as` `function(*)`
) `as` `xs:integer`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The fn:function-arity function returns the arity (number of arguments) of the function identified by $function.

Examples

Expression:	`function-arity(substring#2)`
Result:	2
Expression:	`function-arity(function($node) { name($node) })`
Result:	1
Expression:	let $initial := substring(?, 1, 1) return function-arity($initial)
Result:	1

17.1.4 fn:function-annotations

Summary

Returns the annotations of the function identified by a function item.

Signature

`fn:function-annotations`(
`$function`	`as` `function(*)`
) `as` `map(xs:QName, xs:anyAtomicType*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The fn:function-annotations function returns the annotations of the function identified by $function as a map. For each annotation, a map entry is returned: The key is the name of the annotation. The value is a sequence comprising the annotation values, or an empty sequence if the annotation has no values. If a function (for example, a built-in function) has no annotations, an empty map is returned.

Examples

Expression:	declare %private function local:inc($c) { $c + 1 }; function-annotations(local:inc#1)
Result:	map { Q{http://www.w3.org/2012/xquery}private: () }
Expression:	let $old := %local:deprecated('0.1', '0.2') function() {} let $ann := function-annotations($old) return map:keys($ann) \|\| ': ' \|\| string-join(map:values($ann), ', ')
Result:	local:deprecated: 0.1, 0.2
Expression:	`function-annotations(true#0)`
Result:	map { }

17.2 Basic higher-order functions

The following functions take function items as an argument.

Function	Meaning
`fn:apply`	Makes a dynamic call on a function with an argument list supplied in the form of an array.
`fn:chain`	Applies from left to right on an initial argument a chain of functions provided in a sequence.
`fn:do-until`	Processes a supplied value repeatedly, continuing when some condition is false, and returning the value that satisfies the condition.
`fn:every`	Returns `true` if every item in the input sequence matches a supplied predicate.
`fn:filter`	Returns those items from the sequence `$input` for which the supplied function `$predicate` returns `true`.
`fn:fold-left`	Processes the supplied sequence from left to right, applying the supplied function repeatedly to each item in turn, together with an accumulated result value.
`fn:fold-right`	Processes the supplied sequence from right to left, applying the supplied function repeatedly to each item in turn, together with an accumulated result value.
`fn:for-each`	Applies the function item `$action` to every item from the sequence `$input` in turn, returning the concatenation of the resulting sequences in order.
`fn:for-each-pair`	Applies the function item `$action` to successive pairs of items taken one from `$input1` and one from `$input2`, returning the concatenation of the resulting sequences in order.
`fn:highest`	Returns those items from a supplied sequence that have the highest value of a sort key, where the sort key can be computed using a caller-supplied function.
`fn:index-where`	Returns the position in an input sequence of items that match a supplied predicate.
`fn:lowest`	Returns those items from a supplied sequence that have the lowest value of a sort key, where the sort key can be computed using a caller-supplied function.
`fn:partition`	Partitions a sequence of items into a sequence of non-empty arrays containing the same items, starting a new partition when a supplied condition is true.
`fn:ranks`	Sorts the items of a supplied sequence based on the value of one or more sort keys, grouping the results so that items with the same key appear together as members of the same array, ordered by increasing key value.
`fn:scan-left`	Produces the complete (ordered) sequence of all partial results from every new value the accumulator is assigned to during the evaluation of fn:fold-left.
`fn:scan-right`	Produces the complete (ordered) sequence of all partial results from every new value the accumulator is assigned to during the evaluation of fn:fold-right.
`fn:some`	Returns `true` if at least one item in the input sequence matches a supplied predicate.
`fn:sort`	Sorts a supplied sequence, based on the value of a number of sort keys supplied as functions.
`fn:sort-with`	Sorts a supplied sequence, according to the order induced by the supplied comparator functions.
`fn:subsequence-where`	Returns a contiguous sequence of items from `$input`, with the start and end points located by applying predicates.
`fn:take-while`	Returns items from the input sequence prior to the first one that fails to match a supplied predicate.
`fn:transitive-closure`	Returns all the nodes reachable from a given start node by applying a supplied function repeatedly.
`fn:while-do`	Processes a supplied value repeatedly, continuing while some condition remains true, and returning the first value that does not satisfy the condition.

With all these functions, if the caller-supplied function fails with a dynamic error, this error is propagated as an error from the higher-order function itself.

17.2.1 fn:apply

Summary

Makes a dynamic call on a function with an argument list supplied in the form of an array.

Signature

`fn:apply`(
`$function`	`as` `function(*)`,
`$arguments`	`as` `array(*)`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The result of the function is obtained by invoking the supplied function $function with arguments taken from the members of the supplied array $arguments. The first argument of the function call is the first member of $arguments, the second argument is the second member of $array, and so on.

The arity of the supplied function $function must be the same as the size of the array $array.

The effect of calling fn:apply($f, [$a, $b, $c, ...]) is the same as the effect of the dynamic function call $f($a, $b, $c, ....). For example, the function conversion rules are applied to the supplied arguments in the usual way.

Error Conditions

A dynamic error is raised if the arity of the function $function is not the same as the size of the array $array ([err:FOAP0001]).

Notes

The function is useful where the arity of a function item is not known statically.

Examples

Expression	Result
`apply(concat#3, ["a", "b", "c"])`	"abc"
The expression `apply($f, array:subarray(["a", "b", "c", "d", "e", "f"], 1, function-arity($f)))` calls the supplied function `$f` supplying the number of arguments required by its arity.

17.2.2 fn:chain

Summary

Applies from left to right on an initial argument a chain of functions provided in a sequence.

Signature

`fn:chain`(
`$input`	`as` `item()*`,
`$functions`	`as` `function()`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function behaves as follows:

If $functions is empty, then $input is returned. Else,
The first function in $functions is applied on the provided $input.
Then the next function in $functions (if such exists), is applied on the result, and so on...
Finally the last function in $functions is applied on the latest-result obtained so far, and the result of this final function application is the result of calling fn:chain($input, $functions) .

More formally, the function is equivalent to the following implementation in XPath:

let $chain := (
let $apply := function($x, $f)  {
  fn:apply($f,
    if(function-arity($f) eq 1) then [$x]
    else if($x instance of array(*)) then $x 
    else array{$x}
  )
}
return function($input as item()*, $functions as function(*)*) as item()* {
  fold-left($functions, $input, $apply)
}           
)

Error Conditions

A type error is raised [err:FOAP0001] if the current result does not match the arity and the type(s) of the argument(s) of the next function in the chain, that is, it is a sequence or an array of M items/members and M ne function-arity(current-function) or [err:FORG0006] if the items /members of the current result cannot be coerced to the required types of the arguments of the next function.

Notes

Contrary to the right-to-left evaluation of function-composition as defined in Math, here the functions in $functions are evaluated in their order from left-to-right (the first function is evaluated first, then the second,..., and the last function is evaluated last).
It is not a requirement that every function in $functions must have arity of one. In fact, each of these functions can have any arity.
For a function with arity N, greater than 1, the result produced by the application of the previous function must be either a sequence with N items, or, if some of the parameters of the function could be sequences themselves, then an array withN members, and each of these N members is passed by the implementation in the function call as the corresponding argument of this function.
A consequence of the provided rules is that a type error occurs if the current result does not match the arity and the type(s) of the argument(s) of the next function in the chain, that is, it is a sequence or an array of M items/members and M ne function-arity(current-function) or the items /members of the current result cannot be coerced to the required types of the arguments of the next function.
In very simple cases, when it may be possible to use short and meaningful static expressions, one could consider using chaining provided via the arrow operators. In all such cases one should carefully consider the fact that any such desicion could result in longer and less-understandable expressions, would involve one or more operators (not needed if fn:chain is used), and the loss of reusability.

In the following examples it is assumed that these definitions are in scope:

(: The functions below: $incr, $times, $doubleAll, and $range, etc... 
   are needed only for the following examples :)
let $incr := function($x) {op("+")($x, ?)},
    $times := function($y) {op("*")($y,  ?)},
    $doubleAll := function($nums as xs:numeric*) {$nums ! op("*")(., 2)},
    $appendAll := function($strings as xs:string*, $addage as xs:string) 
                {$strings ! concat#2(., $addage)},
    $makeUpperAll := function($strings as xs:string*) {$strings ! upper-case(.)},
    $countAll := function($ar as array(*)) 
                {for $i in 1 to array:size($ar) return count($ar($i))},
    $product3 := function($x, $y, $z) {  $x * $y * $z},
    $range := function($n as xs:integer) {1 to $n}

Examples

Variables
let $incr := function($x) {op("+")($x, ?)}
let $doubleAll := function($nums as xs:numeric) {$nums ! op("")(., 2)}
let $times := function($y) {op("*")($y, ?)}
let $appendAll := function($strings as xs:string*, $addage as xs:string) {$strings ! concat#2(., $addage)}
let $makeUpperAll := function($strings as xs:string*) {$strings ! upper-case(.)}
let $countAll := function($ar as array(*)) {for $i in 1 to array:size($ar) return count($ar($i))}
let $product3 := function($x, $y, $z) { $x * $y * $z}
let $range := function($n as xs:integer) {1 to $n}

Expression:	chain( (2, 3), ($doubleAll, op("+"), $incr(3)))
Result:	13
Expression:	chain( (2, 3), ($doubleAll, sum#1, $incr(3)))
Result:	13
Expression:	chain( (2, 3), (op("+"), $incr(3)))
Result:	8
Expression:	chain( (2, 3), (sum#1, $incr(3)))
Result:	8
Expression:	chain( [1, (), 2, 3], (array:size#1, $incr(3)) )
Result:	7
Expression:	chain( (1, 2, 3), (count#1, $incr(3)) )
Result:	6
Expression:	chain( [1, 2, 3], (count#1, $incr(3)) )
Result:	4
Expression:	chain( 5, ($range, $doubleAll, sum#1) )
Result:	30
Expression:	chain( 2, ($range, $doubleAll, op("*")) )
Result:	8
Expression:	chain( [(1,2,3), ()], ($countAll, op("+")) )
Result:	3
Expression:	chain( [(1,2,3), (), (5, 6)], ($countAll, sum#1) )
Result:	5
Expression:	chain( [(1,2,3), (), (5, 6)], ($countAll, $product3) )
Result:	0
Expression:	chain( "abra cadabra", (tokenize#2(?, " "), string-join#2(?, "+")) )
Result:	"abra+cadabra"
Expression:	chain( "The cat sat on the mat", ( tokenize#2(?, " "), $appendAll(?, "."), $makeUpperAll, string-join#2(?, " ") ) )
Result:	"THE. CAT. SAT. ON. THE. MAT."
Expression:	chain( ( chain( ("A long message ", " long "), (head#1, normalize-space#1, normalize-unicode#1) ), chain( ("A long message ", " long "), (tail#1, normalize-space#1, normalize-unicode#1) ) ), (contains#2) )
Result:	true()
Expression:	chain( (), true#0)
Result:	true()
Expression:	chain(3, (array:append([1], ?), op("+")))
Result:	4
Expression:	chain((1, 2, 3), ($product3, $product3))
Result:	Raises error FOAP0001.
Expression:	chain((1, 2, 3, 4), $product3)
Result:	Raises error FOAP0001.

History

New in 4.0. Accepted 2022-10-20.

17.2.3 fn:do-until

Summary

Processes a supplied value repeatedly, continuing when some condition is false, and returning the value that satisfies the condition.

Signature

`fn:do-until`(
`$input`	`as` `item()*`,
`$action`	`as` `function(item(), xs:integer) as item()`,
`$predicate`	`as` `function(item()*, xs:integer) as xs:boolean`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function behaves as follows:

$pos is initially set to 1.
$action($input, $pos) is evaluated, and the resulting value is used as a new $input.
$predicate($input, $pos) is evaluated. If the result is true, the function returns the value of $input. Otherwise , the process repeats from step 2 with $pos incremented by 1.

More formally, the function is equivalent to the following implementation in XQuery:

declare %private function do-until-helper(
  $input     as item()*,
  $action    as function(item()*, xs:integer) as item()*,
  $predicate as function(item()*, xs:integer) as xs:boolean,
  $pos       as xs:integer
) as item()* {
  let $result := $action($input, $pos)
  return if ($predicate($result, $pos)) then (
    $result
  ) else (
    do-until-helper($result, $action, $predicate, $pos + 1)
  )
};

declare function do-until(
  $input     as item()*,
  $action    as function(item()*, xs:integer) as item()*,
  $predicate as function(item()*, xs:integer) as xs:boolean
) as item()* {
  do-until-helper($input, $action, $predicate, 1)
};

Notes

Do-until loops are very common in procedural programming languages, and this function provides a way to write functionally clean and interruptible iterations without side-effects. A new value is computed and tested until a given condition fails. Depending on the use case, the value can be a simple atomic item or an arbitrarily complex data structure.

The function fn:while-do can be used to perform the action after the first predicate test.

Note that, just as when writing recursive functions, it is easy to construct infinite loops.

Examples

Expression:	do-until( (), fn($value, $pos) { $value, $pos * $pos }, fn($value) { foot($value) > 50 } )
Result:	1, 4, 9, 16, 25, 36, 49, 64 (The loop is interrupted once the last value of the generated sequence is greater than 50.)
Expression:	do-until( (1, 0), fn($value) { $value[1] + $value[2], $value }, fn($value) { avg($value) > 10 } )
Result:	55, 34, 21, 13, 8, 5, 3, 2, 1, 1, 0 (The computation is continued as long as the average of the first Fibonacci numbers is smaller than 10.)

History

New in 4.0.

17.2.4 fn:every

Summary

Returns true if every item in the input sequence matches a supplied predicate.

Signature

`fn:every`(
`$input`	`as` `item()*`,
`$predicate`	`as` `(function(item(), xs:integer) as xs:boolean)?`	`:=` `fn:identity#1`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the value of the expression:

every $boolean in (
  for $item at $pos in $input
  return $predicate($item, $pos)
) satisfies $boolean = true()

Notes

If the second argument is omitted or an empty sequence, the first argument must be a sequence of xs:boolean values.

The implementation may deliver a result as soon as one item is found for which the predicate returns false; it is not required to evaluate the predicate for every item.

Examples

Expression:	`every(())`
Result:	true()
Expression:	`every((1=1, 2=2, 3=4))`
Result:	false()
Expression:	`every((), boolean#1)`
Result:	true()
Expression:	`every((1, 3, 7), function { . mod 2 = 1 })`
Result:	true()
Expression:	`every(-5 to +5, function { . ge 0 })`
Result:	false()
Expression:	every( ("January", "February", "March", "April", "September", "October", "November", "December"), contains(?, "r") )
Result:	true()
Expression:	every( ("January", "February", "March", "April", "September", "October", "November", "December") =!> contains("r") )
Result:	true()
Expression:	`every(1 to 5, fn($num, $pos) { $num = $pos })`
Result:	true()
Expression:	let $dl := <dl> <dt>Morgawr</dt> <dd>Sea giant</dd> </dl> return every($dl/*, fn($elem, $pos) { name($elem) = ( if (($pos mod 2)) then "dt" else "dd" ) })
Result:	true()

History

New in 4.0. Accepted 2022-09-13.

17.2.5 fn:filter

Summary

Returns those items from the sequence $input for which the supplied function $predicate returns true.

Signature

`fn:filter`(
`$input`	`as` `item()*`,
`$predicate`	`as` `function(item(), xs:integer) as xs:boolean`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the value of the expression:

for $item at $pos in $input
where $predicate($item, $pos)
return $item

Error Conditions

As a consequence of the function signature and the function calling rules, a type error occurs if the supplied $predicate function returns anything other than a single xs:boolean item; there is no conversion to an effective boolean value.

Notes

If $predicate is an arity-1 function, the function call fn:filter($input, $predicate) has a very similar effect to the expression $input[$predicate(.)]. There are some differences, however. In the case of fn:filter, the function $F is required to return a boolean; there is no special treatment for numeric predicate values, and no conversion to an effective boolean value. Also, with a filter expression $input[$predicate(.)], the focus within the predicate is different from that outside; this means that the use of a context-sensitive function such as fn:lang#1 will give different results in the two cases.

Examples

Expression:	`filter(1 to 10, function($a) {$a mod 2 = 0})`
Result:	(2, 4, 6, 8, 10)
Expression:	`filter((), lang("en", ?))`
Result:	()
Expression:	let $sequence := (1, 1, 2, 3, 4, 4, 5) return filter( $sequence, fn($item, $pos) { $item = $sequence[$pos - 1] } )
Result:	(1, 4)

History

Changed in 4.0: Positional parameter added to predicate function.

17.2.6 fn:fold-left

Summary

Processes the supplied sequence from left to right, applying the supplied function repeatedly to each item in turn, together with an accumulated result value.

Signature

`fn:fold-left`(
`$input`	`as` `item()*`,
`$zero`	`as` `item()*`,
`$action`	`as` `function(item(), item(), xs:integer) as item()`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function is equivalent to the following implementation in XQuery:

declare %private function fold-left-helper(
  $input  as item()*,
  $zero   as item()*,
  $action as function(item()*, item(), xs:integer) as item()*,
  $pos    as xs:integer
) as item()* {
  if (empty($input))
  then $zero
  else fold-left-helper(
    tail($input),
    $action($zero, head($input), $pos + 1),
    $action,
    $pos + 1
  )
};

declare function fold-left(
  $input  as item()*,
  $zero   as item()*,
  $action as function(item()*, item(), xs:integer) as item()*
) as item()* {
  fold-left-helper($input, $zero, $action, 1)
};

Error Conditions

As a consequence of the function signature and the function calling rules, a type error occurs if the supplied function $action cannot be applied to two arguments, where the first argument is either the value of $zero or the result of a previous application of $action, and the second is any single item from the sequence $input.

Notes

This operation is often referred to in the functional programming literature as “folding” or “reducing” a sequence. It takes a function that operates on a pair of values, and applies it repeatedly, with an accumulated result as the first argument, and the next item in the sequence as the second argument. The accumulated result is initially set to the value of the $zero argument, which is conventionally a value (such as zero in the case of addition, one in the case of multiplication, or a zero-length string in the case of string concatenation) that causes the function to return the value of the other argument unchanged.

The value of the third argument of $action corresponds to the position of the item in the input sequence. It is initally set to 1.

Examples

Expression:	fold-left( 1 to 5, 0, function($a, $b) { $a + $b } )
Result:	15 (This returns the sum of the items in the sequence).
Expression:	fold-left( (2,3,5,7), 1, function($a, $b) { $a * $b } )
Result:	210 (This returns the product of the items in the sequence).
Expression:	fold-left( (true(), false(), false()), false(), function($a, $b) { $a or $b } )
Result:	true() (This returns `true` if any item in the sequence has an effective boolean value of `true`).
Expression:	fold-left( (true(), false(), false()), false(), function($a, $b) { $a and $b } )
Result:	false() (This returns `true` only if every item in the sequence has an effective boolean value of `true`).
Expression:	fold-left( 1 to 5, (), function($a, $b) { $b, $a } )
Result:	(5,4,3,2,1) (This reverses the order of the items in a sequence).
Expression:	fold-left( 1 to 5, "", concat(?, ".", ?) )
Result:	".1.2.3.4.5"
Expression:	fold-left( 1 to 5, "$zero", concat("$f(", ?, ", ", ?, ")") )
Result:	"$f($f($f($f($f($zero, 1), 2), 3), 4), 5)"
Expression:	fold-left( 1 to 5, map { }, function($map, $n) { map:put($map, $n, $n * 2) } )
Result:	map{1:2, 2:4, 3:6, 4:8, 5:10}
Expression:	let $input := (11 to 21, 21 to 31) let $search := 21 return fold-left($input, (), fn($result, $curr, $pos) { $result, if($curr = $search) { $pos } } )
Result:	(11, 12)

History

Changed in 4.0: Positional parameter added to action function.

17.2.7 fn:fold-right

Summary

Processes the supplied sequence from right to left, applying the supplied function repeatedly to each item in turn, together with an accumulated result value.

Signature

`fn:fold-right`(
`$input`	`as` `item()*`,
`$zero`	`as` `item()*`,
`$action`	`as` `function(item(), item(), xs:integer) as item()`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function is equivalent to the following implementation in XQuery:

declare %private function fold-right-helper(
  $input  as item()*,
  $zero   as item()*,
  $action as function(item(), item()*, xs:integer) as item()*,
  $pos    as xs:integer
) as item()* {
  if (empty($input))
  then $zero
  else $action(
    head($input),
    fold-right-helper(tail($input), $zero, $action, $pos - 1),
    $pos
  )
};

declare function fold-right(
  $input  as item()*,
  $zero   as item()*,
  $action as function(item(), item()*, xs:integer) as item()*
) as item()* {
  fold-right-helper($input, $zero, $action, count($input))
};

Error Conditions

As a consequence of the function signature and the function calling rules, a type error occurs if the supplied function $action cannot be applied to two arguments, where the first argument is any item in the sequence $input, and the second is either the value of $zero or the result of a previous application of $action.

Notes

This operation is often referred to in the functional programming literature as “folding” or “reducing” a sequence. It takes a function that operates on a pair of values, and applies it repeatedly, with the next item in the sequence as the first argument, and the result of processing the remainder of the sequence as the second argument. The accumulated result is initially set to the value of the $zero argument, which is conventionally a value (such as zero in the case of addition, one in the case of multiplication, or a zero-length string in the case of string concatenation) that causes the function to return the value of the other argument unchanged.

In cases where the function performs an associative operation on its two arguments (such as addition or multiplication), fn:fold-right produces the same result as fn:fold-left.

The value of the third argument of $action corresponds to the position of the item in the input sequence. Thus, in contrast to fn:fold-left, it is initally set to the number of items in the input sequence.

Examples

Expression:	fold-right( 1 to 5, 0, function($a, $b) { $a + $b } )
Result:	15 (This returns the sum of the items in the sequence).
Expression:	fold-right( 1 to 5, "", concat(?, ".", ?) )
Result:	"1.2.3.4.5."
Expression:	fold-right( 1 to 5, "$zero", concat("$f(", ?, ", ", ?, ")") )
Result:	"$f(1, $f(2, $f(3, $f(4, $f(5, $zero)))))"
Expression:	let $input := (11 to 21, 21 to 31) let $search := 21 return fold-right($input, (), fn($curr, $result, $pos) { $result, $pos[$curr = $search] } )
Result:	(12, 11)

History

Changed in 4.0: Positional parameter added to action function.

17.2.8 fn:for-each

Summary

Applies the function item $action to every item from the sequence $input in turn, returning the concatenation of the resulting sequences in order.

Signature

`fn:for-each`(
`$input`	`as` `item()*`,
`$action`	`as` `function(item(), xs:integer) as item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the value of the expression (provided that ordering mode is ordered):

for $item at $pos in $input
return $action($item, $pos)

Examples

Expression:	`for-each(1 to 5, function($a) { $a * $a })`
Result:	(1, 4, 9, 16, 25)
Expression:	for-each( ("john", "jane"), string-to-codepoints#1 )
Result:	(106, 111, 104, 110, 106, 97, 110, 101)
Expression:	`for-each(("23", "29"), xs:int#1)`
Result:	(23, 29)
Expression:	for-each( ('one', 'two', 'three'), fn($item, $pos) { $pos \|\| '. ' \|\| $item } )
Result:	("1. one", "2. two", "3. three")

History

First introduced in 3.1.Changed in 4.0: Positional parameter added to action function; the specification has been formalized.

17.2.9 fn:for-each-pair

Summary

Applies the function item $action to successive pairs of items taken one from $input1 and one from $input2, returning the concatenation of the resulting sequences in order.

Signature

`fn:for-each-pair`(
`$input1`	`as` `item()*`,
`$input2`	`as` `item()*`,
`$action`	`as` `function(item(), item(), xs:integer) as item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the value of the expression:

for $pos in 1 to min(count($input1), count($input2))
return $action($input1[$pos], $input2[$pos], $pos)

Notes

If one sequence is longer than the other, excess items in the longer sequence are ignored.

Examples

Expression:	for-each-pair( ("a", "b", "c"), ("x", "y", "z"), concat#2 )
Result:	("ax", "by", "cz")
Expression:	for-each-pair( 1 to 5, 1 to 5, function($a, $b) { 10 * $a + $b } )
Result:	(11, 22, 33, 44, 55)
Expression:	let $s := 1 to 8 return for-each-pair($s, tail($s), function($a, $b) { $a * $b })
Result:	(2, 6, 12, 20, 30, 42, 56)
Expression:	for-each-pair( (1, 8, 2), (3, 4, 3), fn($item1, $item2, $pos) { $pos \|\| ': ' \|\| max(($item1, $item2)) } )
Result:	("1: 3", "2: 8", "3: 3")

History

Changed in 4.0: Positional parameter added to action function.

17.2.10 fn:highest

Summary

Returns those items from a supplied sequence that have the highest value of a sort key, where the sort key can be computed using a caller-supplied function.

Signature

`fn:highest`(
`$input`	`as` `item()*`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`,
`$key`	`as` `function(item()) as xs:anyAtomicType*`	`:=` `fn:data#1`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

Rules

The second argument, $collation, defaults to ().

Supplying an empty sequence as $collation is equivalent to supplying fn:default-collation(). For more information on collations see 5.3.5 Choosing a collation.

The third argument defaults to the function data#1.

Let $modified-key be the function:

function($item) {
  $key($item) => data() ! (
    if (. instance of xs:untypedAtomic)
    then xs:double(.)
    else .
  )
}

That is, the supplied function for computing key values is wrapped in a function that converts any xs:untypedAtomic values in its result to xs:double. This makes the function consistent with the behavior of fn:min and fn:max, but inconsistent with fn:sort, which treats untyped values as strings.

The result of the function is obtained as follows:

If the input is an empty sequence, the result is an empty sequence.
The input sequence is sorted, by applying the function fn:sort($input, $collation, $modified-key).
Let $C be the selected collation, or the default collation where applicable.
Let $B be the last item in the sorted sequence.
The function returns those items $A from the input sequence such that (fn:deep-equal($key($A), $key($B), $C), retaining their order.

Error Conditions

If the set of computed keys contains xs:untypedAtomic values that are not castable to xs:double then operation will fail with a dynamic error ([err:FORG0001]^FO).

If the set of computed keys contains values that are not comparable using the lt operator then the sort operation will fail with a type error ([err:XPTY0004]^XP).

Examples

Variables
let $e := <a x="10" y="5" z="2"/>

Expression:	`highest($e/@*) ! name()`
Result:	("x") (By default, untyped values are compared as numbers.)
Expression:	`highest($e/@*, (), string#1) ! name()`
Result:	("y") (Here, the attribute values are compared as strings.)
Expression:	`highest(("red", "green", "blue"), (), string-length#1)`
Result:	("green")
Expression:	highest( ("red", "green", "blue"), (), map { "red" : xs:hexBinary('FF0000'), "green": xs:hexBinary('008000'), "blue" : xs:hexBinary('0000FF') } )
Result:	("red")
Expression:	highest( ("red", "orange", "yellow", "green", "blue", "indigo", "violet"), (), string-length#1 )
Result:	("orange", "yellow", "indigo", "violet")
Expression:	`highest(1 to 25, (), function { . idiv 10 })`
Result:	(20, 21, 22, 23, 24, 25)
To find employees having the highest salary:
highest($employees, (), function { xs:decimal(salary) })

History

New in 4.0. Accepted 2022-09-20.

17.2.11 fn:index-where

Summary

Returns the position in an input sequence of items that match a supplied predicate.

Signature

`fn:index-where`(
`$input`	`as` `item()*`,
`$predicate`	`as` `function(item(), xs:integer) as xs:boolean`
) `as` `xs:integer*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The result of the function is a sequence of integers, in monotonic ascending order, representing the 1-based positions in the input sequence of those items for which the supplied predicate function returns true.

More formally, the function is equivalent to the following expression in XQuery:

for $item at $pos in $input
where $predicate($item, $pos)
return $pos

Examples

Expression:	`index-where((), boolean#1)`
Result:	()
Expression:	`index-where((0, 4, 9), boolean#1)`
Result:	(2, 3)
Expression:	`index-where(1 to 10, function { . mod 2 = 0 })`
Result:	(2, 4, 6, 8, 10)
Expression:	index-where( ("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"), contains(?, "r") )
Result:	(1, 2, 3, 4, 9, 10, 11, 12)
Expression:	index-where( ( 1, 8, 2, 7, 3 ), fn($item, $pos) { $item < 5 and $pos > 2 } )
Result:	(3, 5)

History

New in 4.0. Accepted 2022-09-20.

17.2.12 fn:lowest

Summary

Returns those items from a supplied sequence that have the lowest value of a sort key, where the sort key can be computed using a caller-supplied function.

Signature

`fn:lowest`(
`$input`	`as` `item()*`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`,
`$key`	`as` `function(item()) as xs:anyAtomicType*`	`:=` `fn:data#1`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

Rules

The second argument, $collation, defaults to ().

Supplying an empty sequence as $collation is equivalent to supplying fn:default-collation(). For more information on collations see 5.3.5 Choosing a collation.

The third argument defaults to the function data#1.

Let $modified-key be the function:

function($item) {
  $key($item) => data() ! (
    if (. instance of xs:untypedAtomic) then xs:double(.) else .
  )
}

The result of the function is obtained as follows:

If the input is an empty sequence, the result is an empty sequence.
The input sequence is sorted, by applying the function fn:sort($input, $collation, $modified-key).
Let $C be the selected collation, or the default collation where applicable.
Let $B be the first item in the sorted sequence.
The function returns those items $A from the input sequence such that (fn:deep-equal($key($A), $key($B), $C), retaining their order.

Error Conditions

If the set of computed keys contains xs:untypedAtomic values that are not castable to xs:double then operation will fail with a dynamic error ([err:FORG0001]^FO).

If the set of computed keys contains values that are not comparable using the lt operator then the sort operation will fail with a type error ([err:XPTY0004]^XP).

Examples

Variables
let $e := <a x="10" y="5" z="2"/>

Expression:	`lowest($e/@*) ! name()`
Result:	("z") (By default, untyped values are compared as numbers.)
Expression:	`lowest($e/@*, (), string#1) ! name()`
Result:	("x") (Here, the attribute values are compared as strings.)
Expression:	`lowest(("red", "green", "blue"), (), string-length#1)`
Result:	("red")
Expression:	lowest( ("red", "green", "blue"), (), map { "red" : xs:hexBinary('FF0000'), "green": xs:hexBinary('008000'), "blue" : xs:hexBinary('0000FF') } )
Result:	("blue")
Expression:	lowest( ("April", "June", "July", "August"), (), string-length#1 )
Result:	("June", "July")
Expression:	`lowest(1 to 25, (), function { . idiv 10 })`
Result:	(1, 2, 3, 4, 5, 6, 7, 8, 9)
To find employees having the lowest salary:
lowest($employees, (), function { xs:decimal(salary) })

History

New in 4.0. Accepted 2022-09-20.

17.2.13 fn:partition

Summary

Partitions a sequence of items into a sequence of non-empty arrays containing the same items, starting a new partition when a supplied condition is true.

Signature

`fn:partition`(
`$input`	`as` `item()*`,
`$split-when`	`as` `function(item()*, item(), xs:integer) as xs:boolean`
) `as` `array(item())*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function starts by creating a partition containing the first item in the input sequence, if any. For each remaining item J in the input sequence, other than the first, it calls the supplied $split-when function with three arguments: the contents of the current partition, the item J, and the current position in the input sequence.

Each partition is a sequence of items; the function result wraps each partition as an array, and returns the sequence of arrays.

If the $split-when function returns true, the current partition is wrapped as an array and added to the result, and a new current partition is created, initially containing the item J only. If the $split-when function returns false, the item J is added to the current partition.

More formally, the function returns the result of the expression:

fold-left($input, (), fn($partitions, $next, $pos) {
  if (empty($partitions) or $split-when(foot($partitions)?*, $next, $pos))
  then ($partitions, [ $next ])
  else (trunk($partitions), array { foot($partitions)?*, $next })
})

Notes

The function enables a variety of positional grouping problems to be solved. For example:

partition($input, function($a, $b) { count($a) eq 3 } partitions a sequence into fixed size groups of length 3.
partition($input, function($a, $b) { boolean($b/self::h1) } starts a new group whenever an h1 element is encountered.
partition($input, function($a, $b) { $b lt foot($a) } starts a new group whenever an item is encountered whose value is less than the value of the previous item.

The callback function is not called to process the first item in the input sequence, because this will always start a new partition. The first argument to the callback function (the current partition) is always a non-empty sequence.

Examples

Expression:	partition( ("Anita", "Anne", "Barbara", "Catherine", "Christine"), function($partition, $next) { substring(head($partition),1,1) ne substring($next,1,1) } )
Result:	(["Anita", "Anne"], ["Barbara"], ["Catherine", "Christine"])
Expression:	partition( (1, 2, 3, 4, 5, 6, 7), function($partition, $next) { count($partition) eq 2 } )
Result:	([1, 2], [3, 4], [5, 6], [7])
Expression:	partition( (1, 4, 6, 3, 1, 1), function($partition, $next) { sum($partition) ge 5 } )
Result:	([1, 4], [6], [3, 1, 1])
Expression:	partition( tokenize("In the beginning was the word"), function($partition, $next) { sum(($partition, $next) ! string-length()) gt 10 } )
Result:	(["In", "the"], ["beginning"], ["was", "the", "word"])
Expression:	partition( (1, 2, 3, 6, 7, 9, 10), function($partition, $next) { $next != foot($partition) + 1 } )
Result:	([1, 2, 3], [6, 7], [9, 10])
Expression:	partition( ('a', 'b', 'c', 'd', 'e'), fn($all, $next, $p) { $p mod 2 = 1 } )
Result:	["a", "b"], ["c", "d"], ["e"]

History

Proposed for 4.0

17.2.14 fn:ranks

Summary

Sorts the items of a supplied sequence based on the value of one or more sort keys, grouping the results so that items with the same key appear together as members of the same array, ordered by increasing key value.

Signature

`fn:ranks`(
`$input`	`as` `item()*`,
`$collations`	`as` `xs:string*`	`:=` `fn:default-collation()`,
`$keys`	`as` `(function(item()) as xs:anyAtomicType)`	`:=` `fn:data#1`,
`$orders`	`as` `enum('ascending', 'descending')*`	`:=` `'ascending'`
) `as` `array(item())*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The effect of the function is equivalent to first sorting the input sequence by applying the fn:sort function with the same arguments, and then partitioning the result into a sequence of arrays so that adjacent items with the same sort key go into the same array.

That is, the result of the function is given by the expression:

sort($input, $collations, $keys, $orders) =>
   partition(split-when := fn($group, $item) {
      not(op:same-sort-keys(foot($group), 
                            $item, 
                            $collations, 
                            $keys))})

where op:same-sort-keys($item1, $item2, $collations, $keys) is a function that returns true if and only if the first two arguments have pairwise equal sort key values as defined in the rules of the fn:sort function.

Error Conditions

The errors that may be raised are the same as for fn:sort.

Examples

Expression:	ranks(("red", "orange", "yellow", "green", "blue", "indigo", "violet"), (), string-length#1)
Result:	["red"], ["blue"], ["green"], ["orange", "yellow", "indigo", "violet"]
Expression:	ranks((3, 2, 4), (), fn($n) {$n mod 2})
Result:	[2, 4], [3]
Expression:	ranks((-2, -1, 0, 1, 2, 3), (), fn($n) {$n * $n})
Result:	[0], [-1, 1], [-2, 2], [3]
Expression:	let $group := map { "Argentina" : (2, 0, 1), "Poland" : (1, 1, 1), "Mexico" : (1, 1, 1), "Saudi Arabia" : (1, 0, 2) } return ranks(map:keys($group), (), fn($team){3 * $group($team)[1] + $group($team)[2]}, "descending"))
Result:	["Argentina"], ["Poland", "Mexico"], ["Saudi Arabia"]
Expression:	let $decompose := fn($s as xs:string) { let $chars := characters($s)[. ne ' '], $frequencies := map:build($chars, value:=fn{1}, combine:=op('+')) => map:pairs() => sort((), fn{?key}) return string-join($frequencies ! (?key, ?value), '') } return ranks (("apple macintosh", "astronomer", "angered", "brush", "dictionary", "dirty room", "editor", "enraged", "eleven plus two", "indicatory", "laptop machines", "redo it", "dormitory", "shrub", "moon starer", "twelve plus one"), keys := $decompose )
Result:	["astronomer", "moon starer"], ["apple macintosh", "laptop machines"], ["editor", "redo it"], ["dirty room", "dormitory"], ["eleven plus two", "twelve plus one"], ["dictionary", "indicatory"], ["angered", "enraged"], ["brush", "shrub"]

History

Proposed for 4.0

17.2.15 fn:scan-left

Summary

Produces the complete (ordered) sequence of all partial results from every new value the accumulator is assigned to during the evaluation of fn:fold-left.

Signature

`fn:scan-left`(
`$input`	`as` `item()*`,
`$zero`	`as` `item()*`,
`$action`	`as` `function(item(), item()) as item()`
) `as` `array()`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function is equivalent to the following implementation in XPath (return clause added in comments for completeness):

let $scan-left-inner := function($input as item()*, 
                                 $zero as item()*, 
                                 $action as function(item()*, item()) as item()*,
                                 $self as function(*)
                               ) as array(*)*                               
{
  let $result := [$zero]
   return
     if(empty($input)) then $result
       else
         (
           $result, $self(tail($input), $action($zero, head($input)), $action, $self)  
         )
},

$scan-left := function($input as item()*, 
                       $zero as item()*, 
                       $action as function(item()*, item()) as item()*
                     ) as array(*)*  
{
  $scan-left-inner($input, $zero, $action, $scan-left-inner)
}
(:
  return
    $scan-left(1 to 10, 0, op('+'))  
:)

Error Conditions

Notes

Note that each intermediate result is placed in a separate singleton array. This is necessary because we cannot represent a sequence of results, some or all of which are a sequence - that is "sequence of sequences" as just a single sequence.

Examples

Expression:	scan-left(1 to 10, 0, op('+'))
Result:	[0], [1], [3], [6], [10], [15], [21], [28], [36], [45], [55]
Expression:	scan-left(1 to 3, 0, op('-'))
Result:	[0], [-1], [-3], [-6]
Produce the intermediate results of mapping each number in a sequence to its doubled value. This example shows the necessity to place each intermediate result (sequence) into a singleton array - otherwise the sequence of sequences (intermediate results) would not be possible to express as a single sequence without losing completely the intermediate results.
Expression:	let $double := fn($x){2 * $x} return scan-left(1 to 5, (), fn($seq, $it){$seq , $double($it)})
Result:	[()], [2], [(2,4)], [(2,4,6)], [(2,4,6,8)], [(2,4,6,8,10)]
Produce the factorials of all numbers from 0 to 10
Expression:	scan-left(1 to 10, 1, op('*'))
Result:	[1], [1], [2], [6], [24], [120], [720], [5040], [40320], [362880], [3628800]

History

Proposed for 4.0

17.2.16 fn:scan-right

Summary

Produces the complete (ordered) sequence of all partial results from every new value the accumulator is assigned to during the evaluation of fn:fold-right.

Signature

`fn:scan-right`(
`$input`	`as` `item()*`,
`$zero`	`as` `item()*`,
`$action`	`as` `function(item(), item()) as item()`
) `as` `array()`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function is equivalent to the following implementation in XPath (return clause in comments added for completeness):

let  $scan-right-inner := function($input as item()*,
                          $zero as item()*,
                          $action as function(item()*, item()) as item()*,                          
                          $self as function(*)
                         ) as array(*)*
{
    if(empty($input)) then [$zero] 
      else
        let $rightResult := $self(tail($input), $zero, $action, $self)
         return
            ([$action(head($input), head($rightResult))], $rightResult)
},

$scan-right := function($input as item()*,
                        $zero as item()*,
                        $f as function(item()*, item()) as item()*
                       ) as array(*)*
{
  $scan-right-inner($input, $zero, $f, $scan-right-inner)
}        
(:
return
  $scan-right(1 to 10, 0, op('+'))  
:)

Error Conditions

As a consequence of the function signature and the function calling rules, a type error occurs if the supplied function $action cannot be applied to two arguments, where the first argument is any item in the sequence $input, and the second is either the value of $zero or the result of a previous application of $action.

Notes

Note that each intermediate result is placed in a separate singleton array. This is necessary because we cannot represent a sequence of results, some or all of which are a sequence - that is "sequence of sequences" as just a single sequence.

Examples

Expression:	scan-right(1 to 10, 0, op('+'))
Result:	[55], [54], [52], [49], [45], [40], [34], [27], [19], [10], [0]
Expression:	scan-right(1 to 3, 0, op('-'))
Result:	[2], [-1], [3], [0]

History

Proposed for 4.0

17.2.17 fn:some

Summary

Returns true if at least one item in the input sequence matches a supplied predicate.

Signature

`fn:some`(
`$input`	`as` `item()*`,
`$predicate`	`as` `(function(item(), xs:integer) as xs:boolean)?`	`:=` `fn:identity#1`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the value of the expression:

some $boolean in (
  for $item at $pos in $input
  return $predicate($item, $pos)
) satisfies $boolean = true()

Notes

If the second argument is omitted or an empty sequence, the first argument must be a sequence of xs:boolean values.

The implementation may deliver a result as soon as one item is found for which the predicate returns true; it is not required to evaluate the predicate for every item.

Examples

Expression:	`some(())`
Result:	false()
Expression:	`some((1=1, 2=2, 3=4))`
Result:	true()
Expression:	`some((), boolean#1)`
Result:	false()
Expression:	`some((1, 3, 7), function {. mod 2 = 1 })`
Result:	true()
Expression:	`some(-5 to +5, function {. ge 0 })`
Result:	true()
Expression:	some( ("January", "February", "March", "April", "September", "October", "November", "December"), contains(?, "z") )
Result:	false()
Expression:	some( ("January", "February", "March", "April", "September", "October", "November", "December") =!> contains("r") )
Result:	true()
Expression:	`some(reverse(1 to 5), fn($num, $pos) { $num = $pos })`
Result:	true()

History

New in 4.0. Accepted 2022-09-13.

17.2.18 fn:sort

Summary

Sorts a supplied sequence, based on the value of a number of sort keys supplied as functions.

Signature

`fn:sort`(
`$input`	`as` `item()*`,
`$collations`	`as` `xs:string*`	`:=` `fn:default-collation()`,
`$keys`	`as` `(function(item()) as xs:anyAtomicType)`	`:=` `fn:data#1`,
`$orders`	`as` `enum('ascending', 'descending')*`	`:=` `'ascending'`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

Rules

The result of the function is a sequence that contains all the items from $input, typically in a different order, the order being defined by the supplied sort key definitions.

A sort key definition has three parts:

A sort key function, which is applied to each item in the input sequence to determine a sort key value.
A collation, which is used when comparing sort key values that are of type xs:string or xs:untypedAtomic.
An order direction, which is ascending or descending.

The number of sort key definitions is determined by the number of function items supplied in the $keys argument. If the argument is absent or empty, the default is a single sort key definition using the function data#1.

The $nth sort key definition (where $n counts from one (1)) is established as follows:

The sort key function is $keys[$n] otherwise data#1.
The collation is $collations[$n] otherwise $collations[last()] otherwise default-collation(). That is, it is the collation supplied in the corresponding item of the supplied $collations argument; or in its absence, the last entry in $collations; or if $collations is absent or empty, the default collation from the static context of the caller.
The order direction is $orders[$n] otherwise $orders[last()] otherwise "ascending". That is, it is "ascending" or "descending" according to the value of the corresponding item in the supplied $orders argument; or in its absence, the last entry in $orders; or if $orders is absent or empty, then "ascending".

When comparing values of types other than xs:string or xs:untypedAtomic, the corresponding collation is ignored, and no error is reported if the supplied value is not a known or valid collation name. If it is necessary to supply such an ignored value (for example, in the case where a non-string sort key is followed by another sort key that requires a collation) the empty string can be supplied.

The result of the function is obtained as follows:

The result sequence contains the same items as the input sequence $input, but generally in a different order.
The sort key definitions are established as described above. The sort key definitions are in major-to-minor order. That is, the position of two items $A and $B in the result sequence is determined first by the relative magnitude of their primary sort key values, which are computed by evaluating the sort key function in the first sort key definition. If those two sort key values are equal, then the position is determined by the relative magnitude of their secondary sort key values, computed by evaluating the sort key function in the second sort key definition, and so on.
When a pair of corresponding sort key values of $A and $B are found to be not equal, then $A precedes $B in the result sequence if both the following conditions are true, or if both conditions are false:
1. The sort key value for $A is less than the sort key value for $B, as defined below.
2. The order direction in the corresponding sort key definition is "ascending".
If all the sort key values for $A and $B are pairwise equal, then $A precedes $B in the result sequence if and only if $A precedes $B in the input sequence.

Note:

That is, the sort is stable.
Each sort key value for a given item is obtained by applying the sort key function of the corresponding sort key definition to that item. The result of this function is in the general case a sequence of atomic values. Two sort key values $a and $b are compared as follows:
1. Let $C be the collation in the corresponding sort key definition.
2. Let $REL be the result of evaluating op:lexicographic-compare($key($A), $key($B), $C) where op:lexicographic-compare($a, $b, $C) is defined as follows:
```
if (empty($a) and empty($b)) then 0 
else if (empty($a)) then -1
else if (empty($b)) then +1
else let $rel = op:simple-compare(head($a), head($b), $C)
     return if ($rel eq 0)
            then op:lexicographic-compare(tail($a), tail($b), $C)
            else $rel
```
3. Here op:simple-compare($k1, $k2, $C) is defined as follows:
```
if ($k1 instance of union(xs:string, xs:anyURI, xs:untypedAtomic)
    and $k2 instance of union(xs:string, xs:anyURI, xs:untypedAtomic))
then compare($k1, $k2, $C)
else if ($k1 instance of xs:numeric and $k2 instance of xs:numeric)
then compare($k1, $k2)
else if ($k1 eq $k2) then 0
else if ($k2 lt $k2) then -1
else +1
```
  Note:
  
  This raises an error if two keys are not comparable, for example if one is a string and the other is a number, or if both belong to a non-ordered type such as xs:QName.
4. If $REL is zero, then the two sort key values are deemed equal; if $REL is -1 then $a is deemed less than $b, and if $REL is +1 then $a is deemed greater than $b

Error Conditions

If the set of computed sort keys contains values that are not comparable using the lt operator then the sort operation will fail with a type error ([err:XPTY0004]^XP).

Notes

XSLT and XQuery both provide native sorting capability, but earlier releases of XPath provided no sorting functionality for use in standalone environments.

In addition there are cases where this function may be more flexible than the built-in sorting capability for XQuery or XSLT, for example when the sort key or collation is chosen dynamically, or when the sort key is a sequence of items rather than a single item.

The results are compatible with the results of XSLT sorting (using xsl:sort) in the case where the sort key evaluates to a sequence of length zero or one, given the options stable="yes".

The results are compatible with the results of XQuery sorting (using the order by clause) in the case where the sort key evaluates to a sequence of length zero or one, given the options stable, ascending, and empty least.

The function has been enhanced in 4.0 to allow multiple sort keys to be defined, each potentially with a different collation, and to allow sorting in descending order.

The effect of the XQuery option empty least|greatest, which controls whether the empty sequence is sorted before or after all other values, can be achieved by adding an extra sort key definition that evaluates whether or not the actual sort key is empty (when sorting boolean values, false precedes true).

Supplying too many items in the $collations and/or $orders arguments is not an error; the excess values are ignored except for type-checking against the function signature.

Examples

Expression:	`sort((1, 4, 6, 5, 3))`
Result:	(1, 3, 4, 5, 6)
Expression:	`sort((1, 4, 4e0, 6, 5, 3), orders := "descending")`
Result:	(6, 5, 4, 4e0, 3, 1)
Expression:	`sort((1, -2, 5, 10, -10, 10, 8), (), abs#1)`
Result:	(1, -2, 5, 8, 10, -10, 10)
To sort a set of strings `$in` using Swedish collation:
let $SWEDISH := "http://www.w3.org/2013/collation/UCA?lang=se" return sort($in, $SWEDISH)
To sort a sequence of employees by last name as the major sort key and first name as the minor sort key, using the default collation:
sort($employees, (), fn{name ! (last, first)})
To sort a sequence of employees first by increasing last name (using Swedish collation order) and then by decreasing salary:
sort($employees, "http://www.w3.org/2013/collation/UCA?lang=se", (fn { name/last }, fn { xs:decimal(salary) }), ("ascending", "descending"))

History

Changed in 4.0: Substantially revised in 4.0 to allow multiple sort key definitions.

17.2.19 fn:sort-with

Summary

Sorts a supplied sequence, according to the order induced by the supplied comparator functions.

Signature

`fn:sort-with`(
`$input`	`as` `item()*`,
`$comparators`	`as` `(function(item(), item()) as xs:integer)*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the items of the supplied $input are compared against each other, using the supplied $comparators. The result is a sorted sequence.

Each comparator function takes two items and returns an xs:integer that defines the relationship between these items, in accordance with the fn:compare function:

The comparators are evaluated one after the other, either completely or until the result is an integer other than 0.
If the last integer returned is negative or 0, the first item is returned before the second.
Otherwise, the second item is returned first.

Users are responsible for supplying transitive comparators; otherwise, the result might not be correctly sorted. An example for a non-transitive and thus unsuitable comparator is fn($a, $b) { if($a mod 2 = 1) then 1 else -1 }, as it considers odd numbers to be greater than even numbers.

Sorting is stable, which means that the relative order of the input items is maintained.

More formally, assuming that the comparators raise no errors and are transitive, the effect of the function is equivalent to the following implementation in XQuery:

declare function sort-with(
  $input       as item()*,
  $comparators as (function(item(), item()) as xs:integer)*
) as item()* {
  if (count($input) < 2) then (
    $input
  ) else (
    let $head := head($input), $sorted-tail := sort-with(tail($input), $comparators)
    let $diff := fold-left($comparators, 0, fn($df, $cmp) {
      if($df != 0) then $df else $cmp($head, head($sorted-tail))
    })
    return if ($diff <= 0) then (
      $head, $sorted-tail
    ) else (
      head($sorted-tail), sort-with(($head, tail($sorted-tail)), $comparators)
    )
  )
};

Notes

An implementation is free to choose any sorting algorithm as long as the result returned is stable and matches the result of the implementation in XQuery.

Examples

Expression:	`sort-with((1, 4, 6, 5, 3), compare#2)`
Result:	(1, 3, 4, 5, 6)
Expression:	`sort-with((1, 4, 6, 5, 3), op('-'))`
Result:	(1, 3, 4, 5, 6)
Expression:	`sort-with((1, 4, 4e0, 6, 5, 3), fn($a, $b) { compare($b, $a) })`
Result:	(6, 5, 4, 4e0, 3, 1)
Expression:	sort-with( (1, -2, 5, 10, -12, 8), fn($a, $b) { abs($a) - abs($b) } )
Result:	(1, -2, 5, 8, 10, -12)
Expression:	let $persons := <persons> <person name='Josipa' age='8'/> <person name='Jade' age='6'/> <person name='Jie' age='8'/> </persons> return sort-with($persons/person, ( fn($a, $b) { compare($a/@age, $b/@age) }, fn($a, $b) { compare($a/@name, $b/@name) } ))
Result:	<person name="Jade" age="6"/> <person name="Jie" age="8"/> <person name="Josipa" age="8"/>

History

New in 4.0.

17.2.20 fn:subsequence-where

Summary

Returns a contiguous sequence of items from $input, with the start and end points located by applying predicates.

Signature

`fn:subsequence-where`(
`$input`	`as` `item()*`,
`$from`	`as` `(function(item(), xs:integer) as xs:boolean)?`	`:=` `true#0`,
`$to`	`as` `(function(item(), xs:integer) as xs:boolean)?`	`:=` `false#0`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function returns the subsequence of $input starting with the first item that matches the $from predicate, and ending with the first subsequent item that matches the $to predicate. If $from is not supplied, it defaults to the start of $input; if $to is not supplied, it defaults to the end of $input. If $from does not match any items in $input, the result is the empty sequence; if $to does not match any items, all items up to the last are included in the result.

More formally, the function returns the result of:

let $start := index-where($input, $from)[1] 
              otherwise (count($input) + 1)
let $end :=   index-where($input, $to)[. ge $start][1] 
              otherwise (count($input) + 1)
return slice($input, $start, $end)

Notes

The result includes both the item that matches the $from condition and the item that matches the $to condition. To select a subsequence that starts after the $from item, apply the fn:tail function to the result. To select a subsequence that ends before the $to item, apply the fn:trunk function to the result.

The predicate functions supplied to the $from and $to parameters can include an integer position argument as well as the item itself. This position will always be 1-based, relative to the start of $input. This means it is possible to select items based on their absolute position in the $input sequence, but there is no mechanism to select an end position relative to the start position. If this is needed, the function can be combined with others: for example, to select a subsequence of four items starting with "Barbara", use $input => subsequence-where(fn{. eq "Barbara"}) => slice(end:=4).

If the requirement is to select all elements stopping before the first h2 element if it exists, or up to the end of the sequence otherwise, the simplest solution is perhaps to write:

slice($input, end:=index-where($input, fn{boolean(self::h2)})[1])

Examples

Variables
let $seq := ("Anna", "Barbara", "Catherine", "Delia", "Eliza", "Freda", "Gertrude", "Hilda")

Expression:	`subsequence-where($seq, starts-with(?, "E"))`
Result:	("Eliza", "Freda", "Gertrude", "Hilda")
Expression:	`subsequence-where($seq, to:=starts-with(?, "D"))`
Result:	("Anna", "Barbara", "Catherine", "Delia")
Expression:	`subsequence-where($seq, to:=starts-with(?, "D")) => trunk()`
Result:	("Anna", "Barbara", "Catherine")
Expression:	`subsequence-where($seq, starts-with(?, "E"), starts-with(?, "G"))`
Result:	("Eliza", "Freda", "Gertrude")
Expression:	`subsequence-where($seq, starts-with(?, "D"), fn{string-length(.) gt 5})`
Result:	("Delia", "Eliza", "Freda", "Gertrude")
Expression:	`subsequence-where($seq, starts-with(?, "M"))`
Result:	()
Expression:	`subsequence-where($seq, starts-with(?, "G"), starts-with(?, "Z"))`
Result:	("Gertrude", "Hilda")
Expression:	`subsequence-where($seq)`
Result:	("Anna", "Barbara", "Catherine", "Delia", "Eliza", "Freda", "Gertrude", "Hilda")
Expression:	`subsequence-where($seq, fn($it, $pos){ends-with($it, "a") and $pos gt 5})`
Result:	("Freda", "Gertrude", "Hilda")
Expression:	`subsequence-where($seq, to := fn($it, $pos){ends-with($it, "a") and $pos ge 5})`
Result:	("Anna", "Barbara", "Catherine", "Delia", "Eliza")

17.2.21 fn:take-while

Summary

Returns items from the input sequence prior to the first one that fails to match a supplied predicate.

Signature

`fn:take-while`(
`$input`	`as` `item()*`,
`$predicate`	`as` `function(item(), xs:integer) as item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the result of the XQuery expression:

for $it at $pos in $input
while $predicate($it, $pos)
return $it

That is, it returns all items in the sequence prior to the first one where the result of calling the supplied $predicate function, with the current item and its position as arguments, has an effective boolean value of false.

Notes

There is no analogous drop-while or skip-while function, as found in some functional programming languages. The effect of drop-while($input, $predicate) can be achieved by calling fn:subsequence-where($input, fn{not($predicate(.))}).

Examples

Expression:	`take-while(10 to 20, fn{. le 12})`
Result:	(10, 11, 12)
Expression:	`take-while(10 to 20, fn{. lt 100})`
Result:	(10 to 20)
Expression:	`take-while((), boolean#1)`
Result:	()
Expression:	`take-while(("A", "B", "C", " ", "E"), normalize-space#1)`
Result:	("A", "B", "C")
Expression:	parse-xml("<doc><p/><p/><h2/><img/><p/></doc>")/doc/* => take-while(fn{self::p}) => count()
Result:	2
Expression:	("Aardvark", "Antelope", "Bison", "Buffalo", "Camel", "Dingo") => take-while(starts-with(?, "A"))
Result:	"Aardvark", "Antelope"
Expression:	take-while(10 to 20, fn($num, $pos) { $num lt 18 and $pos lt 4 })
Result:	(10, 11, 12, 13)
Expression:	take-while(characters("ABCD-123"), fn($ch, $pos) {$pos lt 4 and $ch ne '-'}) => string-join#1
Result:	"ABC"
Expression:	take-while("A", "a", "B", "b", "C", "D", "d"), fn($ch, $pos) { matches($ch, if ($pos mod 2 eq 1) then "p{Lu}" else "p{Ll}") })
Result:	"A", "a", "B", "b", "C"

History

New in 4.0. See issue 1002

17.2.22 fn:transitive-closure

Summary

Returns all the nodes reachable from a given start node by applying a supplied function repeatedly.

Signature

`fn:transitive-closure`(
`$node`	`as` `node()?`,
`$step`	`as` `function(node()) as node()*`
) `as` `node()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The value of $node is a node from which navigation starts. If $node is an empty sequence, the function returns an empty sequence.

The value of $step is a function that takes a single node as input, and returns a set of nodes as its result.

The result of the fn:transitive-closure function is the set of nodes that are reachable from $node by applying the $step function one or more times.

Although $step may return any sequence of nodes, the result is treated as a set: the order of nodes in the sequence is ignored, and duplicates are ignored. The result of of the transitive-closure function will always be a sequence of nodes in document order with no duplicates.

The result of the function is equivalent to the following XQuery implementation:

declare %private function tc-inclusive(
  $nodes as node()*,
  $step  as (function(node()) as node()*)
) as node()* {
  let $nextStep := $nodes/$step(.)
  let $newNodes := $nextStep except $nodes
  return if (exists($newNodes))
         then $nodes | tc-inclusive($newNodes, $step)
         else $nodes
};
declare function transitive-closure (
  $node  as node(),
  $step  as (function(node()) as node()*)
) as node()* {
  tc-inclusive($node/$step(.), $step)
};

Note:

Explanation: The private helper function tc-inclusive takes a set of nodes as input, and calls the $step function on each one of those nodes; if the result includes nodes that are not already present in the input, then it makes a recursive call to find nodes reachable from these new nodes, and returns the union of the supplied nodes and the nodes returned from the recursive call (which will always include the new nodes selected in the first step). If there are no new nodes, the recursion ends, returning the nodes that have been found up to this point.

The main function fn:transitive-closure finds the nodes that are reachable from the start node in a single step, and then invokes the helper function tc-inclusive to add nodes that are reachable in multiple steps

Notes

Cycles in the data are not a problem; the function stops searching when it finds no new nodes.

The function may fail to terminate if the supplied $step function constructs and returns new nodes. A processor may detect this condition but is not required to do so.

The $node node is not included in the result, unless it is reachable by applying the $step function one or more times. If a result is required that does include $node, it can be readily added to the result using the union operator: $node | transitive-closure($node, $step).

Examples

Variables

let $data := document{<doc>
   <person id="0"/>
   <person id="1" manager="0"/>
   <person id="2" manager="0"/>
   <person id="3" manager="2"/>
   <person id="4" manager="2"/>
   <person id="5" manager="1"/>
   <person id="6" manager="3"/>
   <person id="7" manager="6"/>
   <person id="8" manager="6"/>
</doc>}

let $direct-reports := function($p as element(person)) as element(person)* {
  $p/../person[@manager=$p/@id]
}

Expression:	transitive-closure( $data//person[@id="2"], $direct-reports )/string(@id)
Result:	("3", "4", "6", "7", "8")
Expression:	transitive-closure( $data, function { child::* } )/@id ! string()
Result:	("0", "1", "2", "3", "4", "5", "6", "7","8")
The following example, given `$root` as the root of an XSLT stylesheet module, returns the URIs of all stylesheet modules reachable using `xsl:import` and `xsl:include` declarations:
transitive-closure($root, fn { document(//(xsl:import\|xsl:include)/@href) }) =!> document-uri()
This example uses the XSLT-defined `document()` function.

17.2.23 fn:while-do

Summary

Processes a supplied value repeatedly, continuing while some condition remains true, and returning the first value that does not satisfy the condition.

Signature

`fn:while-do`(
`$input`	`as` `item()*`,
`$predicate`	`as` `function(item()*, xs:integer) as xs:boolean`,
`$action`	`as` `function(item(), xs:integer) as item()`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function behaves as follows:

$pos is initially set to 1.
$predicate($input, $pos) is evaluated. If the result is false, the function returns the value of $input.
Otherwise, $action($input, $pos) is evaluated, the resulting value is used as a new $input, and the process repeats from step 2 with $pos incremented by 1.

More formally, the function is equivalent to the following implementation in XQuery:

declare %private function while-do-helper(
  $input     as item()*,
  $predicate as function(item()*, xs:integer) as xs:boolean,
  $action    as function(item()*, xs:integer) as item()*,
  $pos       as xs:integer
) as item()* {
  if ($predicate($input, $pos))
  then while-do-helper($action($input, $pos), $predicate, $action, $pos + 1)
  else $input
};

declare function while-do(
  $input     as item()*,
  $predicate as function(item()*, xs:integer) as xs:boolean,
  $action    as function(item()*, xs:integer) as item()*
) as item()* {
  while-do-helper($input, $predicate, $action, 1)
};

Notes

While-do loops are very common in procedural programming languages, and this function provides a way to write functionally clean and interruptible iterations without side-effects. As long as a given condition is met, an new value is computed and tested again. Depending on the use case, the value can be a simple atomic item or an arbitrarily complex data structure.

The function fn:do-until can be used to perform the action before the first predicate test.

Note that, just as when writing recursive functions, it is easy to construct infinite loops.

Examples

Expression:	while-do(2, fn { . <= 100 }, fn { . * . })
Result:	256 (The loop is interrupted as soon as the computed product is greater than 100.)
Expression:	while-do( 1, fn($num, $pos) { $pos <= 10 }, fn($num, $pos) { $num * $pos } )
Result:	3628800 (This returns the factorial of 10, i.e., the product of all integers from 1 to 10.)
Expression:	let $input := (0 to 4, 6 to 10) return while-do( 0, function($n) { $n = $input }, function($n) { $n + 1 } )
Result:	5 (This returns the first positive number missing in a sequence.)
Expression:	while-do( 1 to 9, function($value) { head($value) < 5 }, function($value) { tail($value) } )
Result:	(5, 6, 7, 8, 9) (The first number of a sequence is removed as long as it is smaller than 5.)
Expression:	let $input := 3936256 return while-do( $input, function($result) { abs($result * $result - $input) >= 0.0000000001 }, function($guess) { ($guess + $input div $guess) div 2 } ) => round(5)
Result:	1984 (This computes the square root of a number.)
The following example generates random doubles. It is interrupted once a number exceeds a given limit:
let $result := while-do( random-number-generator(), function($random) { $random?number < 0.8 }, function($random) { map:put($random?next(), 'numbers', ($random?numbers, $random?number)) } ) return $result?numbers

History

New in 4.0.

17.3 Dynamic Evaluation

The following functions allow dynamic loading and evaluation of XQuery queries, XSLT stylesheets, and XPath binary operators.

Function	Meaning
`fn:load-xquery-module`	Provides access to the public functions and global variables of a dynamically loaded XQuery library module.
`fn:transform`	Invokes a transformation using a dynamically loaded XSLT stylesheet.
`fn:op`	Returns a function whose effect is to apply a supplied binary operator to two arguments.

17.3.1 fn:load-xquery-module

Summary

Provides access to the public functions and global variables of a dynamically loaded XQuery library module.

Signature

`fn:load-xquery-module`(
`$module-uri`	`as` `xs:string`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `map(*)`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-dependent·.

Rules

The function loads an implementation-defined set of modules having the target namespace $module-uri.

If the second argument is omitted or an empty sequence, the result is the same as calling the two-argument form with an empty map as the value of the $options argument.

The $options argument can be used to control the way in which the function operates. The ·option parameter conventions· apply.

Key	Meaning
`xquery-version`	The minimum level of the XQuery language that the processor must support. Type: `xs:decimal` Default: `The version given in the prolog of the library module; or implementation-defined if this is absent.`
`location-hints`	A sequence of URIs (in the form of `xs:string` values) which may be used or ignored in an ·implementation-defined· way. Type: `xs:string` Default:* `Empty sequence`
`context-item`	The item to be used as the initial context item when evaluating global variables in the library module. Supplying an empty sequence is equivalent to omitting the entry from the map, and indicates the absence of a context item. If the library module specifies a required type for the context item, then the supplied value must conform to this type, without conversion. Type: `item()?` Default: `Absent`
`variables`	Values for external variables defined in the library module. Values must be supplied for external variables that have no default value, and may be supplied for external variables that do have a default value. The supplied value must conform to the required type of the variable, without conversion. The map contains one entry for each external variable: the key is the variable’s name, and the associated value is the variable’s value. The ·option parameter conventions· do not apply to this contained map. Type: `map(xs:QName, item())` Default:* `An empty map`
`vendor-options`	Values for vendor-defined configuration options for the XQuery processor used to process the request. The key is the name of an option, expressed as a QName: the namespace URI of the QName should be a URI controlled by the vendor of the XQuery processor. The meaning of the associated value is ·implementation-defined·. Implementations should ignore options whose names are in an unrecognized namespace. The ·option parameter conventions· do not apply to this contained map. Type: `map(xs:QName, item())` Default:* `An empty map`

The result of the function is a map R with two entries:

There is an entry whose key is the xs:string value "variables" and whose associated value is a map V. This map (V) contains one entry for each public global variable declared in the library module. The key of the entry is the name of the variable, as an xs:QName value; the associated value is the value of the variable.
There is an entry whose key is the xs:string value "functions" and whose associated value is a map F. This map (F) contains one entry for each distinct QName Q that represents the name of a public and non-external function declared in the library module. The key of the entry is Q, as an xs:QName value; the associated value is a map A. This map (A) contains one entry for each arity N within the arity range of any of the function declarations with the given name; its key is N, as an xs:integer value, and its associated value is a function item obtained as if by evaluating a named function reference Q#N, using the static and dynamic context of the call on fn:load-xquery-module. The function item can be invoked using the rules for dynamic function invocation.

The static and dynamic context of the library module are established according to the rules in Section C Context Components ^XQ31.

It is ·implementation-defined· whether constructs in the library module are evaluated in the same ·execution scope· as the calling module.

The library module that is loaded may import other modules using an import module declaration. The result of fn:load-xquery-module does not include global variables or functions declared in such a transitively imported module. However, the options map supplied in the function call may (and if no default is defined, must) supply values for external variables declared in transitively loaded library modules.

The library module that is loaded may import schema declarations using an import schema declaration. It is ·implementation-defined· whether schema components in the in-scope schema definitions of the calling module are automatically added to the in-scope schema definitions of the dynamically loaded module. The in-scope schema definitions of the calling and called modules must be consistent, according to the rules defined in Section 2.2.5 Consistency Constraints ^XQ31.

Where nodes are passed to or from the dynamically loaded module, for example as an argument or result of a function, they should if possible retain their node identity, their base URI, their type annotations, and their relationships to all other nodes in the containing tree (including ancestors and siblings). If this is not possible, for example because the only way of passing nodes to the chosen XQuery implementation is by serializing and re-parsing, then a node may be passed in the form of a deep copy, which may lose information about the identity of the node, about its ancestors and siblings, about its base URI, about its type annotations, and about its relationships to other nodes passed across the interface.

Error Conditions

If $module-uri is a zero length string, a dynamic error is raised [err:FOQM0001].

If the implementation is not able to find a library module with the specified target namespace, an error is raised [err:FOQM0002].

If a static error (including a statically detected type error) is encountered when processing the library module, a dynamic error is raised [err:FOQM0003].

If a value is supplied for the initial context item or for an external variable and the value does not conform to the required type declared in the dynamically loaded module, a dynamic error is raised [err:FOQM0005].

If no suitable XQuery processor is available, a dynamic error is raised [err:FOQM0006]. This includes (but is not limited to) the following cases:

No XQuery processor is available;
Use of the function has been disabled;
No XQuery processor supporting the requested version of XQuery is available;
No XQuery processor supporting the optional Module Feature is available.

If a dynamic error (including a dynamically detected type error) is encountered when processing the module (for example, when evaluating its global variables), the dynamic error is returned as is.

Notes

If a function declaration F in the loaded module declares (say) four parameters of which one is optional, its arity range will be from 3 to 4, so the result will include two function items corresponding to F#3 and F#4. In the lower-arity function item, F#3, the fourth parameter will take its default value. If the expression that initializes the default value is context sensitive, the static and dynamic context for its evaluation are the static and dynamic contexts of the fn:load-xquery-module function call itself.

As with all other functions in this specification, conformance requirements depend on the host language. For example, a host language might specify that provision of this function is optional, or that it is excluded entirely, or that implementations are required to support XQuery modules using a specified version of XQuery.

Even where support for this function is mandatory, it is recommended for security reasons that implementations should provide a user option to disable its use, or to disable aspects of its functionality.

The load-xquery-module function does not modify the static or dynamic context. Functions and variables from the loaded module become available within the result returned by the function, but they are not added to the static or dynamic context of the caller. This means, for example, that function-lookup will not locate functions from the loaded module.

17.3.2 fn:transform

Summary

Invokes a transformation using a dynamically loaded XSLT stylesheet.

Signature

`fn:transform`(
`$options`	`as` `map(*)`
) `as` `map(*)`

Properties

This function is ·nondeterministic·, ·context-dependent·, and ·focus-independent·.

Rules

This function loads an XSLT stylesheet and invokes it to perform a transformation.

The inputs to the transformation are supplied in the form of a map. The ·option parameter conventions· apply to this map; they do not apply to any nested map unless otherwise specified.

The function first identifies the requested XSLT version, as follows:

If the xslt-version option is present, the requested XSLT version is the value of that option.
Otherwise, the requested XSLT version is the value of the [xsl:]version attribute of the outermost element in the supplied stylesheet or package.

The function then attempts to locate an XSLT processor that implements the requested XSLT version.

If a processor that implements the requested XSLT version is available, then it is used.
Otherwise, if a processor that implements a version later than the requested version is available, then it is used.
Otherwise, the function fails indicating that no suitable XSLT processor is available.

Note:

The phrase locate an XSLT processor includes the possibility of locating a software product and configuring it to act as an XSLT processor that implements the requested XSLT version.

If more than one XSLT processor is available under the above rules, then the one that is chosen may be selected according to the availability of requested features: see below.

Once an XSLT processor has been selected that implements a given version of XSLT, the processor follows the rules of that version of the XSLT specification. This includes any decision to operate in backwards or forwards compatibility mode. For example, if an XSLT 2.0 processor is selected, and the stylesheet specifies version="1.0", then the processor will operate in backwards compatibility mode; if the same processor is selected and the stylesheet specifies version="3.0", the processor will operate in forwards compatibility mode.

The combinations of options that are relevant to each version of XSLT, other than xslt-version itself, are listed below. This is followed by a table giving the meaning of each option.

For invocation of an XSLT 1.0 processor (see [XSL Transformations (XSLT) Version 1.0]), the supplied options must include all of the following (if anything else is present, it is ignored):
1. The stylesheet, provided by supplying exactly one of the following:
  
  stylesheet-location
  stylesheet-node
  stylesheet-text
2. The source tree, provided as the value of the source-node option.
3. Zero or more of the following additional options:
  
  stylesheet-base-uri
  stylesheet-params (defaults to an empty map)
  initial-mode (defaults to the stylesheet’s default mode)
  delivery-format (defaults to document)
  serialization-params (defaults to an empty map)
  enable-messages (default is implementation-defined)
  requested-properties (default is an empty map)
  vendor-options (defaults to an empty map)
  cache (default is implementation-defined)
For invocation of an XSLT 2.0 processor (see [XSL Transformations (XSLT) Version 2.0]), the supplied options must include all of the following (if anything else is present, it is ignored):
1. The stylesheet, provided by supplying exactly one of the following:
  
  stylesheet-location
  stylesheet-node
  stylesheet-text
2. Invocation details, as exactly one of the following:
  1. For apply-templates invocation, all of the following:
    
    source-node
    
    Optionally, initial-mode (defaults to the stylesheet’s default mode)
  2. For call-template invocation, all of the following:
    
    initial-template
    
    Optionally, source-node
3. Zero or more of the following additional options:
  
  stylesheet-base-uri
  stylesheet-params (defaults to an empty map)
  base-output-uri (defaults to absent)
  delivery-format (defaults to document)
  serialization-params (defaults to an empty map)
  enable-messages (default is implementation-defined)
  enable-trace (default is implementation-defined)
  requested-properties (default is an empty map)
  vendor-options (defaults to an empty map)
  cache (default is implementation-defined)
For invocation of an XSLT 3.0 processor (see [XSL Transformations (XSLT) Version 4.0]), the supplied options must include all of the following (if anything else is present, it is ignored):
1. The stylesheet, provided either by supplying exactly one of the following:
  
  stylesheet-location
  stylesheet-node
  stylesheet-text
  
  Or by supplying exactly one of the following:
  
  package-location
  package-node
  package-text
  package-name plus optionally package-version
2. Invocation details, as exactly one of the following combinations:
  1. For apply-templates invocation, all of the following:
    
    Exactly one of source-node or initial-match-selection
    
    Optionally, initial-mode
    
    Optionally, template-params
    
    Optionally, tunnel-params
  2. For call-template invocation using an explicit template name, all of the following:
    
    initial-template
    
    Optionally, template-params
    
    Optionally, tunnel-params
    
    Optionally, source-node
  3. For call-template invocation using the defaulted template name xsl:initial-template, all of the following:
    
    Optionally, template-params
    
    Optionally, tunnel-params
    
    Note:
    
    If the source-node option is present and initial-template is absent, then apply-templates invocation will be used. To use call-template invocation on the template named xsl:initial-template while also supplying a context item for use when evaluating global variables, either (a) supply the context item using the global-context-item option, or (b) supply source-node, and set the initial-template option explicitly to the QName xsl:initial-template
  4. For call-function invocation, all of the following:
    
    initial-function
    
    function-params
  Note:
  
  The invocation method can be determined as the first of the following which applies:
  - If initial-function is present, then call-function invocation.
  - If initial-template is present, then call-template invocation.
  - If source-node or initial-match-selection is present, then apply-templates invocation.
  - Otherwise, call-template invocation using the default entry point xsl:initial-template.
3. Zero or more of the following additional options:
  
  stylesheet-base-uri
  static-params (defaults to an empty map)
  stylesheet-params (defaults to an empty map)
  global-context-item (defaults to absent)
  base-output-uri (defaults to absent)
  delivery-format
  serialization-params (defaults to an empty map)
  enable-assertions (default is false)
  enable-messages (default is implementation-defined)
  enable-trace (default is implementation-defined)
  requested-properties (default is an empty map)
  vendor-options (defaults to an empty map)
  cache (default is implementation-defined)

The meanings of each option are defined in the table below.

Key	Applies to	Value	Meaning
`base-output-uri`	1.0, 2.0, 3.0	The URI of the principal result document; also used as the base URI for resolving relative URIs of secondary result documents. If the value is a relative reference, it is resolved against the static base URI of the `fn:transform` function call. Type: `xs:string` Default: `The effect of not supplying a base output URI is defined by the XSLT specification; the implementation may supply a default, for example the directory containing the stylesheet, or the current working directory.`
`cache`	1.0, 2.0, 3.0	This option has no effect on the result of the transformation but may affect efficiency. The value `true` indicates an expectation that the same stylesheet is likely to be used for more than one transformation; the value `false` indicates an expectation that the stylesheet will be used once only. Type: `xs:boolean` Default: `true()`
`delivery-format`	1.0, 2.0, 3.0	The manner in which the transformation results should be delivered. Applies both to the principal result document and to secondary result documents created using `xsl:result-document`. Type: `xs:string` Default: `document, unless the relevant xsl:output or xsl:result-document element specifies build-tree="no" (applies to XSLT 3.0 only), in which case the default is raw.`
		`document`	The result is delivered as a document node.
		`serialized`	The result is delivered as a string, representing the results of serialization. Note that (as with the `fn:serialize` function) the final encoding stage of serialization (which turns a sequence of characters into a sequence of octets) is either skipped, or reversed by decoding the octet stream back into a character stream.
		`raw`	The result of the initial template or function is returned as an arbitrary XDM value (after conversion to the declared type, but without wrapping in a document node, and without serialization): when this option is chosen, the returned map contains the raw result.
`enable-assertions`	3.0	Indicates whether any `xsl:assert` instructions in the stylesheet are to be evaluated. Type: `xs:boolean` Default: `false()`
`enable-messages`	1.0, 2.0, 3.0	Indicates whether any `xsl:message` instructions in the stylesheet are to be evaluated. The destination and formatting of any such messages is implementation-defined. Type: `xs:boolean` Default: `Implementation-defined`
`enable-trace`	2.0, 3.0	Indicates whether any `fn:trace` functions in the stylesheet are to generate diagnostic messages. The destination and formatting of any such messages is implementation-defined. Type: `xs:boolean` Default: `Implementation-defined`
`function-params`	3.0	An array of values to be used as the arguments to the initial function call. The value is converted to the required type of the declared parameter using the function conversion rules. Type: `array(item())` Default:* `Empty array`
`global-context-item`	3.0	The value of the global context item, as defined in XSLT 3.0 Type: `item()` Default: `The value of source-node`
`initial-function`	3.0	The name of the initial function to be called for call-function invocation. The arity of the function is inferred from the length of `function-params`. Type: `xs:QName` Default: `n/a`
`initial-match-selection`	3.0	The value of the initial match selection, as defined in XSLT 3.0 Type: `item()` Default:* `The value of source-node`
`initial-mode`	1.0, 2.0, 3.0	The name of the initial processing mode. Type: `xs:QName` Default:
`initial-template`	2.0, 3.0	The name of a named template in the stylesheet to act as the initial entry point. Type: `xs:QName` Default: `xsl:initial-template`
`package-name`	3.0	The name of the top-level stylesheet package to be invoked (an absolute URI) Type: `xs:string` Default: `n/a`
`package-location`	3.0	The location of the top-level stylesheet package, as a relative or absolute URI Type: `xs:string` Default: `n/a`
`package-node`	3.0	A document or element node containing the top-level stylesheet package Type: `node()` Default: `n/a`
`package-text`	3.0	The top-level stylesheet package in the form of unparsed lexical XML. Type: `xs:string` Default: `n/a`
`package-version`	3.0	The version of the top-level stylesheet package to be invoked. Type: `xs:string` Default: `"*" (any version)`
`post-process`	1.0 2.0 3.0	A function that is used to post-process each result document of the transformation (both the principal result and secondary results), in whatever form it would otherwise be delivered (document, serialized, or raw). The first argument of the function is the key used to identify the result in the map return by the `fn:transform` function (for example, this will be the supplied base output URI in the case of the principal result, or the string “output” if no base output URI was supplied). The second argument is the actual value. The value that is returned in the result of the `fn:transform` function is the result of applying this post-processing. Note: If the implementation provides a way of writing or invoking functions with side-effects, this post-processing function might be used to save a copy of the result document to persistent storage. For example, if the implementation provides access to the EXPath File library [EXPath], then a serialized document might be written to filestore by calling the `file:write` function. Similar mechanisms might be used to issue an HTTP POST request that posts the result to an HTTP server, or to send the document to an email recipient. The semantics of calling functions with side-effects are entirely ·implementation-defined·. If the primary purpose of the post-processing function is achieved by means of such side-effects, and if the actual results are not needed by the caller of the `fn:transform` function, then it does not matter what the post-processing function actually returns (it could be an empty sequence, for example). Calls to `fn:transform` can potentially have side-effects even in the absence of the post-processing option, because the XSLT specification allows a stylesheet to invoke extension functions that have side-effects. The semantics in this case are ·implementation-defined·. Type: `function(xs:string, item()) as item()` Default: `function($a, $b) { $b }`
`requested-properties`	1.0, 2.0, 3.0	The keys in the map are QNames that could legitimately be supplied in a call to the XSLT `system-property` function; the values in the map are the requested settings of the corresponding property. The boolean values `true()` and `false()` are equivalent to the string values `yes` and `no`. As a special case, setting a value for `xsl:version` has no effect, because of the potential for conflict with other options. For example: Setting `xsl:product-name` to a particular value requests a particular XSLT software product. Setting `xsl:product-version` requests a specific version of that product. Setting `xsl:is-schema-aware` to `true()` requests a schema-aware processor. Setting `xsl:xsd-version` to `"1.1"` requests a processor that supports XML Schema version 1.1. Setting a boolean property such as `xsl:supports-dynamic-evaluation` to `false()` is interpreted as an explicit request for a processor in which the value of the property is `false`. The effect if the requests cannot be precisely met is implementation-defined. In some cases it may be appropriate to ignore the request or to provide an alternative (for example, a later version of the product than the one requested); in other cases it may be more appropriate to raise an error [err:FOXT0001] indicating that no suitable XSLT processor is available. Type: `map(xs:QName, xs:anyAtomicType)` Default: `Empty map`
`serialization-params`	1.0, 2.0, 3.0	Serialization parameters for the principal result document. The supplied map follows the same rules that apply to a map supplied as the second argument of `fn:serialize`. When a parameter is supplied, the corresponding value overrides or augments the value specified in the unnamed `xsl:output` declaration (or its default), following the same rules as when one `xsl:output` declaration overrides another with lower import precedence. When a parameter is supplied and the corresponding value is an empty sequence (for example, `map{"standalone":()}`), any value specified in the unnamed `xsl:output` declaration is overridden by the default value. When a parameter is not supplied in `serialization-params` (that is, when the key is absent) the value that applies is the value appearing in the unnamed `xsl:output` declaration, or its default. Type: `map(xs:anyAtomicType, item())` Default:* `Empty map`
`source-node`	1.0, 2.0, 3.0	When `source-node` is supplied then the `global-context-item` (the context item for evaluating global variables) is the root of the tree containing the supplied node. In addition, for apply-templates invocation, the `source-node` acts as the `initial-match-selection`, that is, stylesheet execution starts by applying templates to this node. Type: `node()` Default: `n/a`
`static-params`	3.0	The values of static parameters defined in the stylesheet; the keys are the names of the parameters, and the associated values are their values. The value is converted to the required type of the declared parameter using the function conversion rules. Type: `map(xs:QName, item())` Default:* `Empty map`
`stylesheet-base-uri`	1.0, 2.0, 3.0	A string intended to be used as the static base URI of the principal stylesheet module. This value must be used if no other static base URI is available. If the supplied stylesheet already has a base URI (which will generally be the case if the stylesheet is supplied using `stylesheet-node` or `stylesheet-location`) then it is ·implementation-defined· whether this parameter has any effect. If the value is a relative reference, it is resolved against the static base URI of the `fn:transform` function call. Type: `xs:string` Default: `n/a`
`stylesheet-location`	1.0, 2.0, 3.0	URI that can be used to locate the principal stylesheet module. If relative, it is resolved against the static base URI of the `fn:transform` function call. The value also acts as the default for stylesheet-base-uri. Type: `xs:string` Default: `n/a`
`stylesheet-node`	1.0, 2.0, 3.0	Root of the tree containing the principal stylesheet module, as a document or element node. The base URI of the node acts as the default for stylesheet-base-uri. Type: `node()` Default: `n/a`
`stylesheet-params`	1.0, 2.0, 3.0	A map holding values to be supplied for stylesheet parameters. The keys are the parameter names; the values are the corresponding parameter values. The values are converted if necessary to the required type using the function conversion rules. The default is an empty map. Type: `map(xs:QName, item())` Default:* `Empty map`
`stylesheet-text`	1.0, 2.0, 3.0	The principal stylesheet module in the form of unparsed lexical XML. Type: `xs:string` Default: `n/a`
`template-params`	3.0	The values of non-tunnel parameters to be supplied to the initial template, used with both apply-templates and call-template invocation. Each value is converted to the required type of the declared parameter using the function conversion rules. Type: `map(xs:QName, item())` Default:*
`tunnel-params`	3.0	The values of tunnel parameters to be supplied to the initial template, used with both apply-templates and call-template invocation. Each value is converted to the required type of the declared parameter using the function conversion rules. Type: `map(xs:QName, item())` Default:* `Empty map`
`vendor-options`	1.0, 2.0, 3.0	Values for vendor-defined configuration options for the XSLT processor used to process the request. The key is the name of an option, expressed as a QName: the namespace URI of the QName should be a URI controlled by the vendor of the XSLT processor. The meaning of the associated value is ·implementation-defined·. Implementations should ignore options whose names are in an unrecognized namespace. Default is an empty map. Type: `map{xs:QName, item()}` Default:* `Empty map`
`xslt-version`	1.0, 2.0, 3.0	The minimum level of the XSLT language that the processor must support. Type: `xs:decimal` Default: `The [xsl:]version attribute at the outermost level of the stylesheet.`

The result of the transformation is returned as a map. There is one entry in the map for the principal result document, and one for each secondary result document. The key is a URI in the form of an xs:string value. The key for the principal result document is the base output URI if specified, or the string "output" otherwise. The key for secondary result documents is the URI of the document, as an absolute URI. The associated value in each entry depends on the requested delivery format. If the delivery format is document, the value is a document node. If the delivery format is serialized, the value is a string containing the serialized result.

Where nodes are passed to or from the transformation, for example as the value of a stylesheet parameter or the result of a function, they should if possible retain their node identity, their base URI, their type annotations, and their relationships to all other nodes in the containing tree (including ancestors and siblings). If this is not possible, for example because the only way of passing nodes to the chosen XSLT implementation is by serializing and re-parsing, then a node may be passed in the form of a deep copy, which may lose information about the identity of the node, about its ancestors and siblings, about its base URI, about its type annotation, and about its relationships to other nodes passed across the interface.

It is ·implementation-defined· whether the XSLT transformation is executed within the same ·execution scope· as the calling code.

The function is ·nondeterministic· in that it is ·implementation-dependent· whether running the function twice against the same inputs produces identical results. The results of two invocations may differ in the identity of any returned nodes; they may also differ in other respects, for example because the value of fn:current-dateTime is different for the two invocations, or because the contents of external documents accessed using fn:doc or xsl:source-document change between one invocation and the next.

Error Conditions

A dynamic error is raised [err:FOXT0001] if the transformation cannot be invoked because no suitable XSLT processor is available. This includes (but is not limited to) the following cases:

No XSLT processor is available;
No XSLT processor supporting the requested version of XSLT is available;
The XSLT processor API does not support some requested feature (for example, the ability to supply tunnel parameters externally);

A dynamic error is raised [err:FOXT0002] if an error is detected in the supplied parameters (for example if two mutually exclusive parameters are supplied).

If a static or dynamic error is reported by the XSLT processor, this function fails with a dynamic error, retaining the XSLT error code.

A dynamic error is raised [err:FOXT0003] if the XSLT transformation invoked by a call on fn:transform fails with a static or dynamic error, and no more specific error code is available.

Note:

XSLT 1.0 does not define any error codes, so this is the likely outcome with an XSLT 1.0 processor. XSLT 2.0 and 3.0 do define error codes, but some APIs do not expose them. If multiple errors are signaled by the transformation (which is most likely to happen with static errors) then the error code should where possible be that of one of these errors, chosen arbitrarily; the processor may make details of additional errors available to the application in an ·implementation-defined· way.

A dynamic error is raised [err:FOXT0004] if the use of this function (or of selected options) has been externally disabled, for example for security reasons.

A dynamic error is raised [err:FOXT0006] if the transformation produces output containing characters available only in XML 1.1, and the calling processor cannot handle such characters.

Recursive use of the fn:transform function may lead to catastrophic failures such as non-termination or stack overflow. No error code is assigned to such conditions, since they cannot necessarily be detected by the processor.

Notes

As with all other functions in this specification, conformance requirements depend on the host language. For example, a host language might specify that provision of this function is optional, or that it is excluded entirely, or that implementations are required to support a particular set of values for the xslt-version parameter.

Examples

The following example loads a stylesheet from the location `render.xsl`, applies it to a document loaded from `test.xml`, and uses an XPath expression to examine the result:
let $result := transform( map { "stylesheet-location" : "render.xsl", "source-node" : doc('test.xml') }) return $result?output//body

17.3.3 fn:op

Summary

Returns a function whose effect is to apply a supplied binary operator to two arguments.

Signature

`fn:op`(
`$operator`	`as` `xs:string`
) `as` `function(item(), item()) as item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The supplied operator must be one of:

",", "and", "or", "+", "-", "*", "div", "idiv", "mod", "=", "<", "<=", ">", ">=", "!=", "eq", "lt", "le", "gt", "ge", "ne", "<<", ">>", "is", "||", "|", "union", "except", "intersect", "to", "otherwise"

The result of calling fn:op("⊙"), where ⊙ is one of the above operators, is the function represented by the XPath expression:

function($x, $y) { $x ⊙ $y }

For example, op("+") returns function($x, $y) { $x + $y }.

Error Conditions

A dynamic error is raised if the supplied argument is not one of the supported operators ([TODO: error code]).

Notes

The function is useful in contexts where an arity-2 callback function needs to be supplied, and a standard operator meets the requirement.

For example, the XSLT xsl:map instruction has an on-duplicates attribute that expects such a function. Specifying on-duplicates="op(',')" is equivalent to specifying on-duplicates="function($x, $y) { $x, $y }

The function is also useful in cases where the choice of operator to apply is made dynamically.

Examples

Expression	Result
`for-each-pair(21 to 25, 1 to 5, op("+"))`	22, 24, 26, 28, 30
`for-each-pair(21 to 25, 1 to 5, op("-"))`	20, 20, 20, 20, 20

History

New in 4.0. Accepted 2022-10-11.

18 Maps

Maps were introduced as a new datatype in XDM 3.1. This section describes functions that operate on maps.

A map is an additional kind of item.

[Definition] A map consists of a set of entries, also known as key-value pairs. Each entry comprises a key which is an arbitrary atomic value, and an arbitrary sequence called the associated value.

[Definition] Within a map, no two entries have the same key. Two atomic values K1 and K2 are the same key for this purpose if the function call fn:atomic-equal($K1, $K2) returns true.

It is not necessary that all the keys in a map should be of the same type (for example, they can include a mixture of integers and strings).

Maps are immutable, and have no identity separate from their content. For example, the map:remove function returns a map that differs from the supplied map by the omission (typically) of one entry, but the supplied map is not changed by the operation. Two calls on map:remove with the same arguments return maps that are indistinguishable from each other; there is no way of asking whether these are “the same map”.

A map can also be viewed as a function from keys to associated values. To achieve this, a map is also a function item. The function corresponding to the map has the signature function($key as xs:anyAtomicValue) as item()*. Calling the function has the same effect as calling the get function: the expression $map($key) returns the same result as get($map, $key). For example, if $books-by-isbn is a map whose keys are ISBNs and whose assocated values are book elements, then the expression $books-by-isbn("0470192747") returns the book element with the given ISBN. The fact that a map is a function item allows it to be passed as an argument to higher-order functions that expect a function item as one of their arguments.

18.1 Composing and Decomposing Maps

It is often useful to decompose a map into a sequence of entries, or key-value pairs (in which the key is an atomic value and the value is an arbitrary sequence). Subsequently it may be necessary to reconstruct a map from these components, typically after modification.

There are two conventional ways of representing key-value pairs, each with its own advantages and disadvantages. Both approaches are supported by functions in this library. These are described below:

[Definition] A singleton map is a map containing a single entry.

It is possible to decompose any map into a sequence of ·singleton maps·, and to construct a map from a sequence of singleton maps.

For example the map map{"x":1, "y":2} can be decomposed to the sequence (map{"x":1}, map{"y":2}).
[Definition] A key-value pair map is a map containing two entries, one (with the key "key") containing the key part of a key value pair, the other (with the key "value") containing the value part of a key value pair.

For example the map map{"x":1, "y":2} can be decomposed as (map{"key":"x", "value":1}, map{"key":"y", "value":2})

A ·key-value pair map· is an instance of the type record(key as xs:anyAtomicType, value as item()*).

The following table summarizes the way in which these two representations can be used to compose and decompose maps:

Operation	Singleton Maps	Key-Value Pair Maps
Decompose a map	`map:entries($map)`	`map:pairs($map)`
Compose a map	`map:merge($entries)`	`map:of-pairs($key-value-pairs)`
Create a single entry	`map:entry($key, $value)`	`map:pair($key, $value)`
Extract the key part of a single entry	`map:keys($entry)`	`$key-value-pair?key`
Extract the value part of a single entry	`map:values($entry)`	`$key-value-pair?value`

18.2 Functions that Operate on Maps

The functions defined in this section use a conventional namespace prefix map, which is assumed to be bound to the namespace URI http://www.w3.org/2005/xpath-functions/map.

The function call map:get($map, $key) can be used to retrieve the value associated with a given key.

There is no operation to atomize a map or convert it to a string. The function fn:serialize can in some cases be used to produce a JSON representation of a map.

Function	Meaning
`map:build`	Returns a map that typically contains one entry for each item in a supplied input sequence.
`map:contains`	Tests whether a supplied map contains an entry for a given key
`map:empty`	Returns `true` if the supplied map contains no entries.
`map:entries`	Returns a sequence containing all the key-value pairs present in a map, each represented as a ·singleton map·.
`map:entry`	Returns a ·singleton map· that represents a single key-value pair.
`map:filter`	Selects entries from a map, returning a new map.
`map:find`	Searches the supplied input sequence and any contained maps and arrays for a map entry with the supplied key, and returns the corresponding values.
`map:for-each`	Applies a supplied function to every entry in a map, returning the concatenation of the results.
`map:get`	Returns the value associated with a supplied key in a given map.
`map:keys`	Returns a sequence containing all the keys present in a map.
`map:keys-where`	Returns a sequence containing selected keys present in a map.
`map:merge`	Returns a map that combines the entries from a number of existing maps.
`map:of-pairs`	Returns a map that combines data from a sequence of ·key-value pair maps·.
`map:pair`	Returns a ·key-value pair map· that represents a single key-value pair.
`map:pairs`	Returns a sequence containing all the key-value pairs present in a map, each represented as a ·key-value pair map·.
`map:put`	Returns a map containing all the contents of the supplied map, but with an additional entry, which replaces any existing entry for the same key.
`map:remove`	Returns a map containing all the entries from a supplied map, except those having a specified key.
`map:replace`	Returns a map based on the contents of an existing map, computing a new value to be associated with a supplied key.
`map:size`	Returns the number of entries in the supplied map.
`map:substitute`	Applies a supplied function to every entry in a map, returning a map whose entries have the same keys as the input, but (potentially) different associated values.
`map:values`	Returns a sequence containing all the values present in a map, in unpredictable order.

18.2.1 map:build

Summary

Returns a map that typically contains one entry for each item in a supplied input sequence.

Signature

`map:build`(
`$input`	`as` `item()*`,
`$keys`	`as` `function(item()) as xs:anyAtomicType*`	`:=` `fn:identity#1`,
`$value`	`as` `function(item()) as item()*`	`:=` `fn:identity#1`,
`$combine`	`as` `function(item(), item()) as item()*`	`:=` `fn:op(',')`
) `as` `map(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function processes each item in $input in order. It calls the $keys function on that item to obtain a sequence of key values, and the $value function to obtain an associated value. Then, for each key value:

If the key is not already present in the target map, the processor adds a new key-value pair to the map, with that key and that value.
If the key is already present, the processor calls the $combine function to combine the existing value for the key with the new value, and replaces the entry with this combined value.

More formally, the function returns the value of the expression:

fold-left($input, map { }, fn($map, $item) {
  let $v := $value($item)
  return fold-left($key($item), $map, fn($m, $k) {
    if (map:contains($m, $k)) then (
      map:put($m, $k, $combine($m($k), $v))
    ) else (
      map:put($m, $k, $v)
    )
  })
})

Notes

Although defined to process the input sequence in order, this is only relevant when combining the entries for duplicate keys.

The default function for both $keys and $value is the identity function. Although it is permitted to default both, this serves little purpose: usually at least one of these arguments will be supplied.

The default action for combining entries with duplicate keys is to perform a sequence-concatenation of the corresponding values, equivalent to the duplicates: combine option on map:merge. Other potentially useful functions for combining duplicates include:

fn($a, $b) { $a } Use the first value and discard the remainder
fn($a, $b) { $b } Use the last value and discard the remainder
fn:concat(?, ",", ?) Form the string-concatenation of the values, comma-separated
fn:op('+') Compute the sum of the values

Examples

Expression:	`map:build((), string#1)`
Result:	map{}
Expression:	`map:build(1 to 10, function { . mod 3 })`
Result:	map{0: (3, 6, 9), 1: (1, 4, 7, 10), 2: (2, 5, 8)} (Returns a map with one entry for each distinct value of `. mod 3`. The function to compute the value is the identity function, and duplicates are combined by sequence concatenation.)
Expression:	map:build( 1 to 5, value := format-integer(?, "w") )
Result:	map{1: "one", 2: "two", 3: "three", 4: "four", 5: "five"} (Returns a map with five entries. The function to compute the key is an identity function, the function to compute the value invokes `fn:format-integer`.)
Expression:	map:build( ("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"), substring(?, 1, 1) )
Result:	map{"A": ("April", "August"), "D": ("December"), "F": ("February"), "J": ("January", "June", "July"), "M": ("March", "May"), "N": ("November"), "O": ("October"), "S": ("September")}
Expression:	map:build( ("apple", "apricot", "banana", "blueberry", "cherry"), substring(?, 1, 1), string-length#1, op("+") )
Result:	map{"a": 12, "b": 15, "c": 6} (Constructs a map where the key is the first character of an input item, and where the corresponding value is the total string-length of the items starting with that character.)
Expression:	let $titles := <titles> <title>A Beginner’s Guide to <ix>Java</ix></title> <title>Learning <ix>XML</ix></title> <title>Using <ix>XML</ix> with <ix>Java</ix></title> </titles> return map:build($titles/title, fn($title) { $title/ix })
Result:	map { "Java": ( <title>A Beginner's Guide to <ix>Java</ix></title>, <title>Using <ix>XML</ix> with <ix>Java</ix></title> ), "XML": ( <title>Learning <ix>XML</ix></title>, <title>Using <ix>XML</ix> with <ix>Java</ix></title> ) }
The following expression creates a map whose keys are employee `@ssn` values, and whose corresponding values are the employee nodes:
map:build(//employee, fn { @ssn })
The following expression creates a map whose keys are employee `@location` values, and whose corresponding values represent the number of employees at each distinct location. Any employees that lack an `@location` attribute will be excluded from the result.
map:build(//employee, fn { @location }, fn { 1 }, op("+"))
The following expression creates a map whose keys are employee `@location` values, and whose corresponding values contain the employee node for the highest-paid employee at each distinct location:
map:build(//employee, function { @location }, combine := fn($a, $b) { highest(($a, $b), fn { xs:decimal(@salary) }) })
The following expression creates a map allowing efficient access to every element in a document by means of its `fn:generate-id` value:
map:build(//*, generate-id#1)

History

Accepted for version 4.0 2022-10-18

18.2.2 map:contains

Summary

Tests whether a supplied map contains an entry for a given key

Signature

`map:contains`(
`$map`	`as` `map(*)`,
`$key`	`as` `xs:anyAtomicType`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function map:contains returns true if the ·map· supplied as $map contains an entry with the ·same key· as $key; otherwise it returns false.

Examples

Variables
let $week := map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Samstag"}

Expression	Result
`map:contains($week, 2)`	true()
`map:contains($week, 9)`	false()
`map:contains(map{}, "xyz")`	false()
`map:contains(map{"xyz":23}, "xyz")`	true()
`map:contains(map{"abc":23, "xyz":()}, "xyz")`	true()

18.2.3 map:empty

Summary

Returns true if the supplied map contains no entries.

Signature

`map:empty`(
`$map`	`as` `map(*)`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns true if and only if $map contains no entries, that is, if map:size($map) eq 0.

Examples

Expression	Result
`map:empty(map {})`	true()
`map:empty(map { 1: () })`	false()

History

New in 4.0

18.2.4 map:entries

Summary

Returns a sequence containing all the key-value pairs present in a map, each represented as a ·singleton map·.

Signature

`map:entries`(
`$map`	`as` `map(*)`
) `as` `map()`

Properties

This function is ·nondeterministic-wrt-ordering·, ·context-independent·, and ·focus-independent·.

Rules

The function map:entries takes any ·map· as its $map argument and returns the key-value pairs that are present in the map as a sequence of ·singleton maps·, in ·implementation-dependent· order.

The function is nondeterministic with respect to ordering (see 1.8.4 Properties of functions). This means that two calls with the same argument are not guaranteed to produce the results in the same order.

The effect of the function is equivalent to the expression:

map:for-each($map, fn($k, $v) { map { $k: $v } })

Examples

Expression

Result

map:entries(
  map { 1: "yes", 2: "no" }
)

(map{1:"yes"}, map{2:"no"})

(or some permutation thereof)

(The result sequence is in ·implementation-dependent· order.)

18.2.5 map:entry

Summary

Returns a ·singleton map· that represents a single key-value pair.

Signature

`map:entry`(
`$key`	`as` `xs:anyAtomicType`,
`$value`	`as` `item()*`
) `as` `map(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function map:entry returns a ·map· which contains a single entry. The key of the entry in the new map is $key, and its associated value is $value.

Notes

The function call map:entry(K, V) produces the same result as the expression map{K : V}.

The function map:entry is intended primarily for use in conjunction with the function map:merge. For example, a map containing seven entries may be constructed like this:

map:merge((
   map:entry("Su", "Sunday"),
   map:entry("Mo", "Monday"),
   map:entry("Tu", "Tuesday"),
   map:entry("We", "Wednesday"),
   map:entry("Th", "Thursday"),
   map:entry("Fr", "Friday"),
   map:entry("Sa", "Saturday")
   ))

The map:merge function can be used to construct a map with a variable number of entries, for example:

map:merge(for $b in //book return map:entry($b/isbn, $b))

Examples

Expression	Result
`map:entry("M", "Monday")`	map{"M":"Monday"}

18.2.6 map:filter

Summary

Selects entries from a map, returning a new map.

Signature

`map:filter`(
`$map`	`as` `map(*)`,
`$predicate`	`as` `function(xs:anyAtomicType, item()) as map()`
) `as` `map(*)`

Properties

This function is ·context-independent·, and ·focus-independent·.

Rules

The function map:filter takes any ·map· as its $map argument and applies the supplied function to each entry in the map; the result is a new map containing those entries for which the function returns true.

The function supplied as $predicate takes two arguments. It is called supplying the key of the map entry as the first argument, and the associated value as the second argument.

Examples

Expression:	map:filter( map { 1: "Sunday", 2: "Monday", 3: "Tuesday", 4:"Wednesday", 5: "Thursday", 6: "Friday", 7: "Saturday" }, function($k, $v) { $k = (1, 7) } )
Result:	map{1:"Sunday", 7:"Saturday"}
Expression:	map:filter( map { 1: "Sunday", 2: "Monday", 3: "Tuesday", 4: "Wednesday", 5: "Thursday", 6:"Friday", 7:"Saturday" }, function($k, $v) { $v = ("Saturday", "Sunday") } )
Result:	map{1:"Sunday", 7:"Saturday"}

History

Proposed for 4.0. Discussed 2022-09-20; decided to defer acceptance pending ideas for alignment with array:filter.

18.2.7 map:find

Summary

Searches the supplied input sequence and any contained maps and arrays for a map entry with the supplied key, and returns the corresponding values.

Signature

`map:find`(
`$input`	`as` `item()*`,
`$key`	`as` `xs:anyAtomicType`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function map:find searches the sequence supplied as $input looking for map entries whose key is the ·same key· as $key. The associated value in any such map entry (each being in general a sequence) is returned as a member of the result array.

The search processes the $input sequence using the following recursively defined rules (any equivalent algorithm may be used provided it delivers the same result, respecting those rules that constrain the order of the result):

To process a sequence, process each of its items in order.
To process an item that is an array, process each of its members in order (each member is, in general, a sequence).
To process an item that is a map, then for each key-value entry (K, V) in the map (in ·implementation-dependent· order) perform both of the following steps, in order:
1. If K is the ·same key· as $key, then add V as a new member to the end of the result array.
2. Process V (which is, in general, a sequence).
To process an item that is neither a map nor an array, do nothing. (Such items are ignored).

Notes

If $input is an empty sequence, map, or array, or if the requested $key is not found, the result will be a zero-length array.

Examples

Variables

let $responses := [map{0:'no', 1:'yes'}, map{0:'non', 1:'oui'}, 
                  map{0:'nein', 1:('ja', 'doch')}]

let $inventory := map{"name":"car", "id":"QZ123", 
      "parts": [map{"name":"engine", "id":"YW678", "parts":[]}]}

Expression	Result
`map:find($responses, 0)`	['no', 'non', 'nein']
`map:find($responses, 1)`	['yes', 'oui', ('ja', 'doch')]
`map:find($responses, 2)`	[]
`map:find($inventory, "parts")`	[[map{"name":"engine", "id":"YW678", "parts":[]}], []]

18.2.8 map:for-each

Summary

Applies a supplied function to every entry in a map, returning the concatenation of the results.

Signature

`map:for-each`(
`$map`	`as` `map(*)`,
`$action`	`as` `function(xs:anyAtomicType, item()) as item()`
) `as` `item()*`

Properties

This function is ·nondeterministic-wrt-ordering·, ·context-independent·, and ·focus-independent·.

Rules

The function map:for-each takes any ·map· as its $map argument and applies the supplied function to each entry in the map, in ·implementation-dependent· order; the result is the sequence obtained by concatenating the results of these function calls.

The function is nondeterministic with respect to ordering (see 1.8.4 Properties of functions). This means that two calls with the same arguments are not guaranteed to process the map entries in the same order.

The function supplied as $action takes two arguments. It is called supplying the key of the map entry as the first argument, and the associated value as the second argument.

Examples

Expression:	map:for-each( map { 1: "yes", 2: "no" }, function($k, $v) { $k } )
Result:	(1,2) (or some permutation thereof) (This function call is equivalent to calling `map:keys`. The result is in implementation-dependent order.)
Expression:	distinct-values( map:for-each( map { 1: "yes", 2: "no" }, function($k, $v) { $v } ) )
Result:	("yes", "no") (or some permutation thereof) (This function call returns the distinct values present in the map, in implementation-dependent order.)
Expression:	map:merge( map:for-each( map { "a": 1, "b": 2 }, function($k, $v) { map:entry($k, $v + 1) } ) )
Result:	map{"a":2, "b":3} (This function call returns a map with the same keys as the input map, with the value of each entry increased by one.)
This XQuery example converts the entries in a map to attributes on a newly constructed element node:
let $dimensions := map{'height': 3, 'width': 4, 'depth': 5}; return <box>{ map:for-each($dimensions, function($k, $v) { attribute { $k } { $v } }) }</box>
The result is the element `<box height="3" width="4" depth="5"/>`.

18.2.9 map:get

Summary

Returns the value associated with a supplied key in a given map.

Signature

`map:get`(
`$map`	`as` `map(*)`,
`$key`	`as` `xs:anyAtomicType`,
`$fallback`	`as` `function(xs:anyAtomicType) as item()*`	`:=` `void#1`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function map:get attempts to find an entry within the ·map· supplied as $map that has the ·same key· as $key. If there is such an entry, it returns the associated value; if not, it invokes the supplied $fallback function, supplying the requested $key value as the argument, and returns the result of this call. The default $fallback function always returns an empty sequence.

Notes

A return value of () from map:get could indicate that the key is present in the map with an associated value of (), or it could indicate that the key is not present in the map. The two cases can be distinguished by calling map:contains, or by using a $fallback function to return a value known never to appear in the map.

The $fallback function can be used in a number of ways:

It might return a conventional value such as NaN to indicate that no matching key was found.
It might raise a dynamic error, by means of a call on fn:error.
It might compute a result algorithmically. For example, if the map holds a table of abbreviations, such as map{'CA':'Canada', 'UK':'United Kingdom', 'US':'United States'}, then specifying fallback := fn:identity#1 has the effect that the key value is returned unchanged if it is not found in the map.

Invoking the ·map· as a function item has the same effect as calling get with no $fallback function: that is, when $map is a map, the expression $map($K) is equivalent to map:get($map, $K). Similarly, the expression map:get(map:get(map:get($map, 'employee'), 'name'), 'first') can be written as $map('employee')('name')('first').

Examples

Variables
let $week := map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Samstag"}

Expression:	`map:get($week, 4)`
Result:	"Donnerstag"
Expression:	`map:get($week, 9)`
Result:	() (When the key is not present, the function returns an empty sequence.)
Expression:	`map:get(map:entry(7,()), 7)`
Result:	() (An empty sequence as the result can also signify that the key is present and the associated value is an empty sequence.)
Expression:	map { 1: "single", 2: "double", 3: "triple" } => map:get(10, function { . \|\| "-fold" })
Result:	"10-fold" (The map holds special cases; the fallback function handles other cases.)

18.2.10 map:keys

Summary

Returns a sequence containing all the keys present in a map.

Signature

`map:keys`(
`$map`	`as` `map(*)`
) `as` `xs:anyAtomicType*`

Properties

This function is ·nondeterministic-wrt-ordering·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function map:keys takes any ·map· as its $map argument and returns the keys that are present in the map as a sequence of atomic values, in ·implementation-dependent· order.

More formally, the function returns the value of the expression:

map:for-each($map, fn($key, $value) { $key })

Notes

The number of items in the result will be the same as the number of entries in the map, and the result sequence will contain no duplicate values.

Examples

Expression Result

map:keys(map { 1: "yes", 2:" no" })

(1, 2)

(or some permutation thereof)

(The result is in ·implementation-dependent· order.)

18.2.11 map:keys-where

Summary

Returns a sequence containing selected keys present in a map.

Signature

`map:keys-where`(
`$map`	`as` `map(*)`,
`$predicate`	`as` `(function(xs:anyAtomicType, item()*) as xs:boolean)`
) `as` `xs:anyAtomicType*`

Properties

This function is ·nondeterministic-wrt-ordering·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function map:keys takes any ·map· as its $map argument. The $predicate function takes the key and the value of the corresponding map entry as an argument, and the result is a sequence containing the keys of those entries for which the predicate function returns true in ·implementation-dependent· order.

More formally, the function returns the value of the expression:

map:for-each($map, fn($key, $value) {
  if($predicate($key, $value)) { $key }
})

Examples

Expression:	let $numbers := map { 0: "zero", 1: "one", 2: "two", 3: "three" } return map:keys-where($numbers, fn($key, $value) { $value = ("two", "three") })
Result:	(2, 3) (or some permutation thereof)
Expression:	let $square := map:merge( (1 to 5) ! map:entry(., . * .) ) return map:keys-where($square, fn($key, $value) { $value > 5 and $value < 20 })
Result:	(3, 4) (or some permutation thereof)
Expression:	let $birthdays := map { "Agnieszka": xs:date("1980-12-31"), "Jabulile": xs:date("2001-05-05"), "Joel": xs:date("1969-11-10"), "Midori": xs:date("2012-01-08") } return map:keys-where($birthdays, fn($name, $date) { starts-with($name, "J") and year-from-date($date) = 1969 })
Result:	"Joel"

18.2.12 map:merge

Summary

Returns a map that combines the entries from a number of existing maps.

Signature

`map:merge`(
`$maps`	`as` `map()`,
`$options`	`as` `map(*)?`	`:=` `map{}`
) `as` `map(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function map:merge returns a map that is formed by combining the contents of the maps supplied in the $maps argument.

Informally, the supplied maps are combined as follows:

There is one entry in the returned map for each distinct key present in the union of the input maps, where two keys are distinct if they are not the ·same key·.
If there are duplicate keys, that is, if two or more maps contain entries having the ·same key·, then the way this is handled is controlled by the second ($options) argument.

The definitive specification is as follows.

If the second argument is omitted or an empty sequence, the effect is the same as calling the two-argument function with an empty map as the value of $options.
The $options argument can be used to control the way in which duplicate keys are handled. The ·option parameter conventions· apply.

The entries that may appear in the $options map are as follows:

Key	Value	Meaning
`duplicates`	Determines the policy for handling duplicate keys: specifically, the action to be taken if two maps in the input sequence `$maps` contain entries with key values `K₁` and `K₂` where `K₁` and `K₂` are the ·same key·. Type: `xs:string` Default: `use-first`
	`reject`	An error is raised [err:FOJS0003] if duplicate keys are encountered.
	`use-first`	If duplicate keys are present, all but the first of a set of duplicates are ignored, where the ordering is based on the order of maps in the `$maps` argument.
	`use-last`	If duplicate keys are present, all but the last of a set of duplicates are ignored, where the ordering is based on the order of maps in the `$maps` argument.
	`use-any`	If duplicate keys are present, all but one of a set of duplicates are ignored, and it is ·implementation-dependent· which one is retained.
	`combine`	If duplicate keys are present, the result map includes an entry for the key whose associated value is the sequence-concatenation of all the values associated with the key, retaining order based on the order of maps in the `$maps` argument. The key value in the result map that corresponds to such a set of duplicates must be the ·same key· as each of the duplicates, but it is otherwise unconstrained: for example if the duplicate keys are `xs:byte(1)` and `xs:short(1)`, the key in the result could legitimately be `xs:long(1)`.

The result of the function call map:merge($MAPS, $OPTIONS) is defined to be consistent with the result of the expression:

let $FOJS0003 := QName("http://www.w3.org/2005/xqt-errors", "FOJS0003")
let $duplicates-handler := map {
  "use-first": function($a, $b) { $a },
  "use-last":  function($a, $b) { $b },
  "combine":   function($a, $b) { $a, $b },
  "reject":    function($a, $b) { fn:error($FOJS0003) },
  "use-any":   function($a, $b) { fn:random-number-generator()?permute(($a, $b))[1] }
}
let $combine-maps := function($A as map(*), $B as map(*), $deduplicator as function(*)) {
  fold-left(map:keys($B), $A, function($z, $k) { 
    if (map:contains($z, $k))
    then map:put($z, $k, $deduplicator($z($k), $B($k)))
    else map:put($z, $k, $B($k))
  })
}
return fold-left($MAPS, map { },
  $combine-maps(?, ?, $duplicates-handler($OPTIONS?duplicates otherwise "use-first"))
)

Note:

By way of explanation, $combine-maps is a function that combines two maps by iterating over the keys of the second map, adding each key and its corresponding value to the first map as it proceeds. The second call of fn:fold-left in the return clause then iterates over the maps supplied in the call to map:merge, accumulating a single map that absorbs successive maps in the input sequence by calling $combine-maps.

This algorithm processes the supplied maps in a defined order, but processes the keys within each map in implementation-dependent order.

The use of fn:random-number-generator represents one possible conformant implementation for "duplicates":"use-any", but it is not the only conformant implementation and is not intended to be a realistic implementation. The purpose of this option is to allow the implementation to use whatever strategy is most efficient; for example, if the input maps are processed in parallel, then specifying "duplicates":"use-any" means that the implementation does not need to keep track of the original order of the sequence of input maps.

Error Conditions

An error is raised [err:FOJS0003] if the value of $options indicates that duplicates are to be rejected, and a duplicate key is encountered.

An error is raised [err:FOJS0005] if the value of $options includes an entry whose key is defined in this specification, and whose value is not a permitted value for that key.

Notes

If the input is an empty sequence, the result is an empty map.

If the input is a sequence of length one, the result map is indistinguishable from the supplied map.

There is no requirement that the supplied input maps should have the same or compatible types. The type of a map (for example map(xs:integer, xs:string)) is descriptive of the entries it currently contains, but is not a constraint on how the map may be combined with other maps.

Examples

Variables
let $week := map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Samstag"}

Expression:	`map:merge(())`
Result:	map{} (Returns an empty map).
Expression:	map:merge(( map:entry(0, "no"), map:entry(1, "yes") ))
Result:	map{0:"no", 1:"yes"} (Returns a map with two entries).
Expression:	map:merge( ($week, map { 7: "Unbekannt" }) )
Result:	map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Samstag", 7:"Unbekannt"} (The value of the existing map is unchanged; the returned map contains all the entries from `$week`, supplemented with an additional entry.)
Expression:	map:merge( ($week, map { 6: "Sonnabend" }), map { "duplicates": "use-last" } )
Result:	map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Sonnabend"} (The value of the existing map is unchanged; the returned map contains all the entries from `$week`, with one entry replaced by a new entry. Both input maps contain an entry with the key `6`; the one used in the result is the one that comes last in the input sequence.)
Expression:	map:merge( ($week, map { 6: "Sonnabend" }), map { "duplicates": "use-first" } )
Result:	map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Samstag"} (The value of the existing map is unchanged; the returned map contains all the entries from `$week`, with one entry replaced by a new entry. Both input maps contain an entry with the key `6`; the one used in the result is the one that comes first in the input sequence.)
Expression:	map:merge( ($week, map { 6: "Sonnabend" }), map { "duplicates": "combine" } )
Result:	map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:("Samstag", "Sonnabend")} (The value of the existing map is unchanged; the returned map contains all the entries from `$week`, with one entry replaced by a new entry. Both input maps contain an entry with the key `6`; the entry that appears in the result is the sequence-concatenation of the entries in the input maps, retaining order.)

18.2.13 map:of-pairs

Summary

Returns a map that combines data from a sequence of ·key-value pair maps·.

Signature

`map:of-pairs`(
`$input`	`as` `record(key as xs:anyAtomicType, value as item())`,
`$combine`	`as` `function(item(), item()) as item()*`	`:=` `fn:op(',')`
) `as` `map(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function map:of-pairs returns a map that is formed by combining ·key-value pair maps· supplied in the $input argument.

The optional $combine argument can be used to define how duplicate keys should be handled. The default is to form the sequence concatenation of the corresponding values, retaining their order in the input sequence.

The effect of the function is equivalent to the expression:

map:pairs($week) => map:build(fn { ?key }, fn { ?value }, $combine)

Error Conditions

The function can be made to fail with a dynamic error in the event that duplicate keys are present in the input sequence by supplying a $combine function that invokes the fn:error function.

Notes

If the input is an empty sequence, the result is an empty map.

There is no requirement that the supplied key-value pairs should have the same or compatible types. The type of a map (for example map(xs:integer, xs:string)) is descriptive of the entries it currently contains, but is not a constraint on how the map may be combined with other maps.

Examples

Variables
let $week := map { 0: "Sonntag", 1: "Montag", 2: "Dienstag", 3: "Mittwoch", 4: "Donnerstag", 5: "Freitag", 6 :"Samstag" }

Expression:	`map:of-pairs(())`
Result:	map{} (Returns an empty map).
Expression:	`map:of-pairs(map:pairs($week))`
Result:	map { 0: "Sonntag", 1: "Montag", 2: "Dienstag", 3: "Mittwoch", 4: "Donnerstag", 5: "Freitag", 6 :"Samstag" } (The function `map:of-pairs` is the inverse of `map:pairs`.)
Expression:	map:of-pairs(( map { "key": 0, "value": "no" }, map { "key": 1, "value": "yes" } ))
Result:	map{0:"no", 1:"yes"} (Returns a map with two entries).
Expression:	map:of-pairs(( map:pairs($week), map { "key": 7, "value": "Unbekannt" } ))
Result:	map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Samstag", 7:"Unbekannt"} (The value of the existing map is unchanged; the returned map contains all the entries from `$week`, supplemented with an additional entry.)
Expression:	map:of-pairs(( map:pairs($week), map { "key": 6, "value": "Sonnabend" } ))
Result:	map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:("Samstag", "Sonnabend")} (The value of the existing map is unchanged; the returned map contains all the entries from `$week`, with one entry replaced by a new entry. Both input maps contain an entry with the key `6`; the one used in the result combines the two supplied values into a single sequence.)
Expression:	map:of-pairs( (map:pairs($week), map { "key": 6, "value": "Sonnabend" }), function($old, $new) { $new } )
Result:	map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Sonnabend"} (The value of the existing map is unchanged; the returned map contains all the entries from `$week`, with one entry replaced by a new entry. Both input maps contain an entry with the key `6`; the supplied `$combine` function ensures that the one used in the result is the one that comes last in the input sequence.)
Expression:	map:of-pairs( (map:pairs($week), map { "key": 6, "value": "Sonnabend" }), function($old, $new) { `{$old}\|{$new}` } )
Result:	map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Samstag\|Sonnabend"} (In the result map, the value for key `6` is obtained by concatenating the values from the two input maps, with a separator character.)

18.2.14 map:pair

Summary

Returns a ·key-value pair map· that represents a single key-value pair.

Signature

`map:pair`(
`$key`	`as` `xs:anyAtomicType`,
`$value`	`as` `item()*`
) `as` `record(key as xs:anyAtomicType, value as item()*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function map:pair returns a ·map· which contains two entries, one (with the key "key") containing $key and the other (with the key "value") containing $value.

Notes

The function call map:pair(K, V) produces the same result as the expression map { "key": K, "value": V }.

The function map:pair is intended primarily for use in conjunction with the function map:of-pairs. A map may be constructed like this:

map:of-pairs((
   map:pair("Su", "Sunday"),
   map:pair("Mo", "Monday"),
   map:pair("Tu", "Tuesday"),
   map:pair("We", "Wednesday"),
   map:pair("Th", "Thursday"),
   map:pair("Fr", "Friday"),
   map:pair("Sa", "Saturday")
   ))

The map:of-pairs function can be used to construct a map with a variable number of entries, for example:

map:of-pairs(//book ! map:pair(./isbn, .))

Examples

Expression	Result
`map:pair("M", "Monday")`	map { "key": "M", "value": "Monday" }

18.2.15 map:pairs

Summary

Returns a sequence containing all the key-value pairs present in a map, each represented as a ·key-value pair map·.

Signature

`map:pairs`(
`$map`	`as` `map(*)`
) `as` `record(key as xs:anyAtomicType, value as item())`

Properties

This function is ·nondeterministic-wrt-ordering·, ·context-independent·, and ·focus-independent·.

Rules

The function map:pairs takes any ·map· as its $map argument and returns the keys that are present in the map as a sequence of ·key-value pair maps·, in ·implementation-dependent· order.

A key-value pair map is an instance of type record(key as xs:anyAtomicType, value as item()*): that is a map with two entries, one (with key "key") holding the key, and the other (with key "value") holding the value.

The effect of the function is equivalent to the expression:

map:for-each($map, fn($k, $v) { map { "key": $k, "value": $v } })

Examples

Expression

Result

map:pairs(
  map { 1: "yes", 2: "no" }
)

(map{"key":1, "value":"yes"}, map{"key":2, "value":"no"})

(or some permutation thereof)

(The result is in ·implementation-dependent· order.)

18.2.16 map:put

Summary

Returns a map containing all the contents of the supplied map, but with an additional entry, which replaces any existing entry for the same key.

Signature

`map:put`(
`$map`	`as` `map(*)`,
`$key`	`as` `xs:anyAtomicType`,
`$value`	`as` `item()*`
) `as` `map(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function map:put returns a ·map· that contains all entries from the supplied $map, with the exception of any entry whose key is the ·same key· as $key, together with a new entry whose key is $key and whose associated value is $value.

The effect of the function call map:put($MAP, $KEY, $VALUE) is equivalent to the result of the following steps:

let $MAP2 := map:remove($MAP, $KEY)

This returns a map in which all entries with the same key as $KEY have been removed.
Construct and return a map containing:
1. All the entries (key/value pairs) in $MAP2, and
2. The entry map:entry($KEY, $VALUE)

Notes

There is no requirement that the type of $key and $value be consistent with the types of any existing keys and values in the supplied map.

Examples

Variables
let $week := map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Samstag"}

Expression Result

map:put($week, 6, "Sonnabend")

map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag",
                  5:"Freitag", 6:"Sonnabend"}

map:put($week, -1, "Unbekannt")

map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag",
                  5:"Freitag", 6:"Samstag", -1:"Unbekannt"}

18.2.17 map:remove

Summary

Returns a map containing all the entries from a supplied map, except those having a specified key.

Signature

`map:remove`(
`$map`	`as` `map(*)`,
`$keys`	`as` `xs:anyAtomicType*`
) `as` `map(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function map:remove returns a ·map· containing all the entries in $map except for any entry whose key is the ·same key· as an item in $keys.

No failure occurs if an item in $keys does not correspond to any entry in $map; that key value is simply ignored.

More formally, the function returns the value of the expression:

map:merge(
  map:for-each($map, fn($k, $v) { 
    if (some $key in $keys satisfies atomic-equal($k, $key))
    then () 
    else map:entry($k, $v)
  })
)

Examples

Variables
let $week := map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Samstag"}

Expression	Result
`map:remove($week, 4)`	map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 5:"Freitag", 6:"Samstag"}
`map:remove($week, 23)`	map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Samstag"}
`map:remove($week, (0, 6 to 7))`	map{1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag"}
`map:remove($week, ())`	map{0:"Sonntag", 1:"Montag", 2:"Dienstag", 3:"Mittwoch", 4:"Donnerstag", 5:"Freitag", 6:"Samstag"}

18.2.18 map:replace

Summary

Returns a map based on the contents of an existing map, computing a new value to be associated with a supplied key.

Signature

`map:replace`(
`$map`	`as` `map(*)`,
`$key`	`as` `xs:anyAtomicType`,
`$action`	`as` `function(item()) as item()`
) `as` `map(*)`

Properties

This function is ·context-independent·, and ·focus-independent·.

Rules

If the supplied $map contains an existing entry for the supplied $key, then the returned map contains an entry for that $key whose value is obtained by applying the supplied $action to the existing value associated with that key.

Otherwise, the returned map contains an entry for the supplied $key whose value is obtained by applying the supplied $action to an empty sequence.

The effect of the function call map:replace($MAP, $KEY, $VALUE) is equivalent to the result of the expression:

if (map:contains($MAP, $KEY)) 
then map:put($MAP, $KEY, $ACTION(map:get($MAP, $KEY)))
else map:put($MAP, $KEY, $ACTION(())

Examples

Expression:	`map:replace(map{1:"alpha", 2:"beta"}, 1, upper-case#1)`
Result:	map { 1: "ALPHA", 2: "beta" }
Expression:	`map:replace(map{1:"alpha", 2:"beta"}, 3, upper-case#1)`
Result:	map { 1: "alpha", 2: "beta" 3: "" }
Expression:	fold-left( ("a", "b", "c", "a"), map { }, function($map, $key) { map:replace($map, $key, function($val) { ($val otherwise 0) + 1 }) } )
Result:	map{"a":2, "b":1, "c":1}

18.2.19 map:size

Summary

Returns the number of entries in the supplied map.

Signature

`map:size`(
`$map`	`as` `map(*)`
) `as` `xs:integer`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function map:size takes any ·map· as its $map argument and returns the number of entries that are present in the map.

Examples

Expression	Result
`map:size(map{})`	0
`map:size(map{"true":1, "false":0})`	2

History

First introduced in 3.1.Functionality unchanged in 4.0, but the specification has been formalized.

18.2.20 map:substitute

Summary

Applies a supplied function to every entry in a map, returning a map whose entries have the same keys as the input, but (potentially) different associated values.

Signature

`map:substitute`(
`$map`	`as` `map(*)`,
`$action`	`as` `function(xs:anyAtomicType, item()) as item()`
) `as` `map(*)`

Properties

This function is ·context-independent·, and ·focus-independent·.

Rules

The function map:substitute takes any ·map· as its $map argument and applies the supplied function to each entry in the map; the result is a map that associates the original set of key values with the results of these function calls.

The function supplied as $action takes two arguments. It is called supplying the key of the map entry as the first argument, and the associated value as the second argument.

Notes

The function call map:substitute($m, $f) returns the same result as map:merge(map:for-each($m, fn($k, $v) { map:entry($k, $f($k, $v)) })).

Examples

Expression:	map:substitute( map { 1: true(), 2: false() }, function($k, $v) { not($v) } )
Result:	map{1:false(), 2:true()}
Expression:	map:substitute( map { 1: "yes", 2: "no" }, function($k, $v) { $v \|\| ' (' \|\| $k \|\| ')' } )
Result:	map{1:"yes (1)", 2:"no (2)"}

18.2.21 map:values

Summary

Returns a sequence containing all the values present in a map, in unpredictable order.

Signature

`map:values`(
`$map`	`as` `map(*)`
) `as` `item()*`

Properties

This function is ·nondeterministic-wrt-ordering·, ·context-independent·, and ·focus-independent·.

Rules

The function map:values takes any ·map· as its $map argument and returns the values that are present in the map as a sequence, in ·implementation-dependent· order.

The effect of the function is equivalent to $map?*.

Examples

Expression

Result

map:values(
  map{ 1: "yes", 2: "no" }
)

("yes", "no")

(or some permutation thereof)

(The result is in ·implementation-dependent· order.)

map:values(
  map {
    1: ("red", "green"),
    2: ("blue", "yellow"),
    3:()
  }
)

("red", "green", "blue", "yellow")

(or some permutation thereof)

(The result is in ·implementation-dependent· order.)

18.3 Other Operations on Maps

Because a map is a function item, functions that apply to functions also apply to maps. A map is an anonymous function, so fn:function-name returns the empty sequence; fn:function-arity always returns 1.

Maps may be compared using the fn:deep-equal function.

There is no function or operator to atomize a map or convert it to a string (other than fn:serialize, which can be used to serialize some maps as JSON texts).

19 Arrays

Arrays were introduced as a new datatype in XDM 3.1. This section describes functions that operate on arrays.

An array is an additional kind of item. An array of size N is a mapping from the integers (1 to N) to a set of values, called the members of the array, each of which is an arbitrary sequence. Because an array is an item, and therefore a sequence, arrays can be nested.

An array acts as a function from integer positions to associated values, so the function call $array($index) can be used to retrieve the array member at a given position. The function corresponding to the array has the signature function($index as xs:integer) as item()*. The fact that an array is a function item allows it to be passed as an argument to higher-order functions that expect a function item as one of their arguments.

19.1 Functions that Operate on Arrays

The functions defined in this section use a conventional namespace prefix array, which is assumed to be bound to the namespace URI http://www.w3.org/2005/xpath-functions/array.

As with all other values, arrays are treated as immutable. For example, the array:reverse function returns an array that differs from the supplied array in the order of its members, but the supplied array is not changed by the operation. Two calls on array:reverse with the same argument will return arrays that are indistinguishable from each other; there is no way of asking whether these are “the same array”. Like sequences, arrays have no identity.

All functionality on arrays is defined in terms of two primitives:

The function array:members decomposes an array to a sequence of value records.
The function array:of-members composes an array from a sequence of value records.

A value record here is an item that encapsulates an arbitrary value; the representation chosen for a value record is record(value as item()*), that is, a map containing a single entry whose key is the string "value" and whose value is the encapsulated sequence.

Function	Meaning
`array:append`	Returns an array containing all the members of a supplied array, plus one additional member at the end.
`array:build`	Returns an array obtained by evaluating the supplied function once for each item in the input sequence.
`array:empty`	Returns `true` if the supplied array contains no members.
`array:filter`	Returns an array containing those members of the `$array` for which `$predicate` returns `true`.
`array:flatten`	Replaces any array appearing in a supplied sequence with the members of the array, recursively.
`array:fold-left`	Evaluates the supplied function cumulatively on successive members of the supplied array.
`array:fold-right`	Evaluates the supplied function cumulatively on successive values of the supplied array.
`array:foot`	Returns the last member of an array, that is `$array(array:size($array))`.
`array:for-each`	Returns an array whose size is the same as `array:size($array)`, in which each member is computed by applying `$function` to the corresponding member of `$array`.
`array:for-each-pair`	Returns an array obtained by evaluating the supplied function once for each pair of members at the same position in the two supplied arrays.
`array:get`	Returns the value at the specified position in the supplied array (counting from 1).
`array:head`	Returns the first member of an array, that is `$array(1)`.
`array:index-of`	Returns a sequence of positive integers giving the positions within the array `$array` of members that are equal to `$search`.
`array:index-where`	Returns the position in an input array of members that match a supplied predicate.
`array:insert-before`	Returns an array containing all the members of the supplied array, with one additional member at a specified position.
`array:join`	Concatenates the contents of several arrays into a single array.
`array:members`	Delivers the contents of an array as a sequence of value records.
`array:of-members`	Constructs an array from the contents of a sequence of value records.
`array:put`	Returns an array containing all the members of a supplied array, except for one member which is replaced with a new value.
`array:remove`	Returns an array containing all the members of the supplied array, except for the members at specified positions.
`array:replace`	Returns an array containing all the members of a supplied array, except for one member which is replaced with a new value, the new value being computed from the previous value.
`array:reverse`	Returns an array containing all the members of a supplied array, but in reverse order.
`array:size`	Returns the number of members in the supplied array.
`array:slice`	Returns an array containing selected members of a supplied input array based on their position.
`array:sort`	Sorts a supplied array, based on the value of a number of sort keys supplied as functions.
`array:split`	Delivers the contents of an array as a sequence of singleton arrays.
`array:subarray`	Returns an array containing all members from a supplied array starting at a supplied position, up to a specified length.
`array:tail`	Returns an array containing all members except the first from a supplied array.
`array:trunk`	Returns an array containing all members except the last from a supplied array.
`array:values`	Returns a sequence with the members of an array.

19.1.1 array:append

Summary

Returns an array containing all the members of a supplied array, plus one additional member at the end.

Signature

`array:append`(
`$array`	`as` `array(*)`,
`$member`	`as` `item()*`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the result is an array whose size is array:size($array) + 1, in which all members in positions 1 to array:size($array) are the same as the members in the corresponding position of $array, and the member in position array:size($array) + 1 is $member.

More formally, the result is the value of the expression array:of-members((array:members($array), map{'value':$member})).

Examples

Expression	Result
`array:append(["a", "b", "c"], "d")`	["a", "b", "c", "d"]
`array:append(["a", "b", "c"], ("d", "e"))`	["a", "b", "c", ("d", "e")]
`array:append(["a", "b", "c"], ["d", "e"])`	["a", "b", "c", ["d", "e"]]

History

First introduced in 3.1.Functionality unchanged in 4.0, but the specification has been formalized

19.1.2 array:build

Summary

Returns an array obtained by evaluating the supplied function once for each item in the input sequence.

Signature

`array:build`(
`$input`	`as` `item()*`,
`$action`	`as` `function(item()) as item()*`	`:=` `fn:identity#1`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

If the function is called with one argument, the effect is the same as calling the two-argument function with fn:identity#1 as the second argument.

Informally, array:build#2 applies the supplied function to each item in the input sequence, and the resulting sequence becomes one member of the returned array.

More formally, array:build#2 returns the result of the expression:

array:of-members($input ! map { 'value': $action(.) })

Notes

The single-argument function array:build($input) is equivalent to the XPath expression array{$input}, but it is useful to have this available as a function.

The two-argument form facilitates the construction of arrays whose members are arbitrary sequences.

Examples

Expression:	`array:build(1 to 5)`
Result:	[1, 2, 3, 4, 5]
Expression:	array:build( 1 to 5, function { 2 * . } )
Result:	[2, 4, 6, 8, 10]
Expression:	array:build( 1 to 5, function { 1 to . } )
Result:	[1, (1,2), (1,2,3), (1,2,3,4), (1,2,3,4,5)]
Expression:	array:build( ("red", "green", "blue"), characters#1 )
Result:	[("r", "e", "d"), ("g", "r", "e", "e", "n"), ("b", "l", "u", "e")]
Expression:	array:build( 1 to 5, function { array { 1 to . } } )
Result:	[[1], [1,2], [1,2,3], [1,2,3,4], [1,2,3,4,5]]

History

Proposed for 4.0.

19.1.3 array:empty

Summary

Returns true if the supplied array contains no members.

Signature

`array:empty`(
`$array`	`as` `array(*)`
) `as` `xs:boolean`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns true if and only if $array contains no members, that is, if array:size($array) eq 0.

Notes

The test for emptiness is not the same as the test used by the xsl:on-empty instruction in XSLT. For example, an array is not considered empty by this function if it contains a single member that is itself an empty array.

Examples

Expression	Result
`array:empty(["a", "b", "c"])`	false()
`array:empty([])`	true()
`array:empty([[]])`	false()
`array:empty([()])`	false()

History

New in 4.0

19.1.4 array:filter

Summary

Returns an array containing those members of the $array for which $predicate returns true.

Signature

`array:filter`(
`$array`	`as` `array(*)`,
`$predicate`	`as` `function(item()*, xs:integer) as xs:boolean`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function returns an array containing those members of the input array that satisfy the supplied predicate.

More formally, the function returns the result of the expression:

array:of-members(
  for member $member in $array
  where $predicate($member, $pos)
  return $member
)

Error Conditions

As a consequence of the function signature and the function calling rules, a type error occurs if the supplied function $function returns anything other than a single xs:boolean item; there is no conversion to an effective boolean value.

Examples

Expression:	array:filter( ["A", "B", 1, 2], function($x) { $x instance of xs:integer } )
Result:	[1, 2]
Expression:	array:filter( ["the cat", "sat", "on the mat"], function { count(tokenize(.)) > 1 } )
Result:	["the cat", "on the mat"]
Expression:	`array:filter(["A", "B", "", 0, 1], boolean#1)`
Result:	["A", "B", 1]
Expression:	let $array := [1, 1, 2, 3, 4, 4, 5] return array:filter( $array, fn($item, $pos) { $pos > 1 and $item = $array($pos - 1) } )
Result:	[1, 4]

History

First introduced in 3.1.Changed in 4.0: Positional parameter added to predicate function; the specification has been formalized.

19.1.5 array:flatten

Summary

Replaces any array appearing in a supplied sequence with the members of the array, recursively.

Signature

`array:flatten`(
`$input`	`as` `item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function processes the items in the supplied sequence $input as follows:

An item that is an array is replaced by its members, retaining order.
Any other item is retained unchanged.

The process is then repeated so long as the sequence contains an array among its items.

The function is equivalent to the following implementation in XQuery:

declare function flatten(
  $input as item()*
) as item()* {
  for $item in $input
  return if ($item instance of array(*)) then flatten(array:values($item)) else $item
};

Notes

The argument to the function will often be a single array item, but this is not essential.

Unlike atomization, this function retains any nodes contained in the array.

Examples

Expression	Result
`array:flatten([1, 4, 6, 5, 3])`	(1, 4, 6, 5, 3)
`array:flatten(([1, 2, 5], [[10, 11], 12], [], 13))`	(1, 2, 5, 10, 11, 12, 13)
`array:flatten([(1,0), (1,1), (0,1), (0,0)])`	(1, 0, 1, 1, 0, 1, 0, 0)

History

First introduced in 3.1.Retained unchanged.

19.1.6 array:fold-left

Summary

Evaluates the supplied function cumulatively on successive members of the supplied array.

Signature

`array:fold-left`(
`$array`	`as` `array(*)`,
`$zero`	`as` `item()*`,
`$action`	`as` `function(item(), item(), xs:integer) as item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function is equivalent to the following expression:

fold-left(
  array:members($array),
  $zero,
  fn($result, $member, $pos) { $action($member?value, $result, $pos) }
)

Notes

If the supplied array is empty, the function returns $zero.

If the supplied array contains a single member $m, the function returns $zero => $action($m).

If the supplied array contains two members $m and $n, the function returns $zero => $action($m) => $action($n); and similarly for an input array with more than two members.

The value of the third argument of $action corresponds to the position of the member in the input array. It is initally set to 1.

Examples

Expression:	array:fold-left( [true(), true(), false()], true(), function($x, $y) { $x and $y } )
Result:	false() (Returns true if every member of the input array has an effective boolean value of `true()`.)
Expression:	array:fold-left( [true(), true(), false()], false(), function($x, $y) { $x or $y } )
Result:	true() (Returns true if at least one member of the input array has an effective boolean value of `true()`.)
Expression:	array:fold-left( [ 1, 2, 3 ], [], function($x, $y) { [ $x, $y ] } )
Result:	[[[[], 1], 2], 3]
Expression:	let $input := array { 11 to 21, 21 to 31 } let $search := 21 return array:fold-left($input, (), fn($result, $curr, $pos) { $result, if($curr = $search) { $pos } } )
Result:	(11, 12)

History

First introduced in 3.1.Changed in 4.0: Positional parameter added to action function; the specification has been formalized.

19.1.7 array:fold-right

Summary

Evaluates the supplied function cumulatively on successive values of the supplied array.

Signature

`array:fold-right`(
`$array`	`as` `array(*)`,
`$zero`	`as` `item()*`,
`$action`	`as` `function(item(), item(), xs:integer) as item()*`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function is equivalent to the following expression:

fold-right(
  array:members($array),
  $zero,
  fn($member, $result, $pos) { $action($member?value, $result, $pos) }
)

Notes

If the supplied array is empty, the function returns $zero.

If the supplied array contains a single member $m, the function returns $action($m, $zero).

If the supplied array contains two members $m and $n, the function returns $action($m, $action($n, $zero)); and similarly for an input array with more than two members.

The value of the third argument of $action corresponds to the position of the member in the input array. Thus, in contrast to array:fold-left, it is initally set to the number of members in the input array.

Examples

Expression:	array:fold-right( [true(), true(), false()], true(), function($x, $y) { $x and $y } )
Result:	false() (Returns true if every member of the input array has an effective boolean value of `true()`.)
Expression:	array:fold-right( [true(), true(), false()], false(), function($x, $y) { $x or $y } )
Result:	true() (Returns true if at least one member of the input array has an effective boolean value of `true()`.)
Expression:	array:fold-right( [ 1, 2, 3 ], [], function($x, $y) { [ $x, $y ] } )
Result:	[1, [2, [3, []]]]
Expression:	let $input := array { 11 to 21, 21 to 31 } let $search := 21 return array:fold-right($input, (), fn($curr, $result, $pos) { $result, if($curr = $search) { $pos } } )
Result:	(12, 11)

History

First introduced in 3.1.Changed in 4.0: Positional parameter added to action function; the specification has been formalized.

19.1.8 array:foot

Summary

Returns the last member of an array, that is $array(array:size($array)).

Signature

`array:foot`(
`$array`	`as` `array(*)`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns last member of $array, that is the value of array:get($array, array:size($array)).

Error Conditions

A dynamic error occurs [err:FOAY0001] if $array is empty.

Examples

Expression	Result
`array:foot([5, 6, 7, 8])`	8
`array:foot([["a", "b"], ["c", "d"]])`	["c", "d"]
`array:foot([("a", "b"), ("c", "d")])`	"c", "d"

History

Proposed and accepted for 4.0, see issue 97

19.1.9 array:for-each

Summary

Returns an array whose size is the same as array:size($array), in which each member is computed by applying $function to the corresponding member of $array.

Signature

`array:for-each`(
`$array`	`as` `array(*)`,
`$action`	`as` `function(item(), xs:integer) as item()`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function returns an array whose members are obtained by applying the supplied $function to each member of the input array in turn.

More formally, the function returns the result of the expression:

for member $member at $pos in $array
return [ $action($member, $pos) ]

Examples

Expression:	array:for-each( [ "A", "B", 1, 2 ], function($z) { $z instance of xs:integer } )
Result:	[false(), false(), true(), true()]
Expression:	array:for-each( [ "the cat", "sat", "on the mat" ], tokenize#1 )
Result:	[("the", "cat"), "sat", ("on", "the", "mat")]
Expression:	array:for-each( [ [ "the", "cat" ], [ "sat" ], [ "on", "the", "mat" ] ], array:flatten#1 )
Result:	[("the", "cat"), "sat", ("on", "the", "mat")]
Expression:	array:for-each( ['one', 'two', 'three'], fn($member, $pos) { $pos \|\| '. ' \|\| $member } )
Result:	["1. one", "2. two", "3. three"]

History

Changed in 4.0: Positional parameter added to action function.

19.1.10 array:for-each-pair

Summary

Returns an array obtained by evaluating the supplied function once for each pair of members at the same position in the two supplied arrays.

Signature

`array:for-each-pair`(
`$array1`	`as` `array(*)`,
`$array2`	`as` `array(*)`,
`$action`	`as` `function(item(), item(), xs:integer) as item()*`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the result of the expression:

array:join(
  for $pos in 1 to min(array:size($input1), array:size($input2))
  return [ $action($input1($pos), $input2($pos), $pos) ]
)

Notes

If the arrays have different size, excess members in the longer array are ignored.

Examples

Expression:	array:for-each-pair( ["A", "B", "C"], [1, 2, 3], function($x, $y) { array { $x, $y }} )
Result:	[["A", 1], ["B", 2], ["C", 3]]
Expression:	let $array := ["A", "B", "C", "D"] return array:for-each-pair( $array, array:tail($array), concat#2 )
Result:	["AB", "BC", "CD"]
Expression:	array:for-each-pair( [1, 8, 2], [3, 4, 3], fn($member1, $member2, $pos) { $pos \|\| ': ' \|\| max(($member1, $member2)) } )
Result:	["1: 3", "2: 8", "3: 3"]

History

First introduced in 3.1.Changed in 4.0: Positional parameter added to action function; the specification has been formalized.

19.1.11 array:get

Summary

Returns the value at the specified position in the supplied array (counting from 1).

Signature

`array:get`(
`$array`	`as` `array(*)`,
`$position`	`as` `xs:integer`,
`$fallback`	`as` `function(xs:integer) as item()*`	`:=` `fn($i) { fn:error(fn:QName('', 'FOAY0001')) }`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function returns the member at a specified position in the array. If $position is less than one or greater than array:size($array), then the $fallback function is called, supplying the value of $position as the argument value; and the result of this call is returned.

The default $fallback function raises a dynamic error. The call on fn:error shown as the default is for illustrative purposes only; apart from the error code (err:FOAY0001) the details of the error (such as the error message) are ·implementation-dependent·.

More formally, the function returns the value of:

if ($position = (1 to array:size($array)))
then array:members($array)[$position]?value 
else $fallback($position)

Error Conditions

In the absence of a $fallback function, a dynamic error occurs [err:FOAY0001] if $position is not in the range 1 to array:size($array) inclusive.

Examples

Expression	Result
`["a", "b", "c"] => array:get(2)`	"b"
`["a", ["b", "c"]] => array:get(2)`	["b", "c"]
`["a"] => array:get(1, void#1)`	"a"
`[] => array:get(1, void#1)`	()

19.1.12 array:head

Summary

Returns the first member of an array, that is $array(1).

Signature

`array:head`(
`$array`	`as` `array(*)`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns first member of $array, that is the value of array:get($array, 1).

Error Conditions

A dynamic error occurs [err:FOAY0001] if $array is empty.

Examples

Expression	Result
`array:head([5, 6, 7, 8])`	5
`array:head([["a", "b"], ["c", "d"]])`	["a", "b"]
`array:head([("a", "b"), ("c", "d")])`	"a", "b"

History

First introduced in 3.1.Unchanged in 4.0.

19.1.13 array:index-of

Summary

Returns a sequence of positive integers giving the positions within the array $array of members that are equal to $search.

Signature

`array:index-of`(
`$input`	`as` `array(*)`,
`$search`	`as` `xs:anyAtomicType*`,
`$collation`	`as` `xs:string?`	`:=` `fn:default-collation()`
) `as` `xs:integer*`

Properties

The two-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and implicit timezone.

The three-argument form of this function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations, and static base URI, and implicit timezone.

Rules

Informally, all members of $array are compared with $search. An array member is equal to the search value if it has the same number of items, and if every item matches the corresponding search item under the rules for the eq operator. Items of type xs:untypedAtomic are compared as if they were of type xs:string. Items that cannot be compared, because the eq operator is not defined for their types, are considered to be distinct. If a member compares equal, then the position of that member is included in the result.

The collation used by this function is determined according to the rules in 5.3.5 Choosing a collation. This collation is used when string comparison is required.

More formally, the function returns the result of the expression:

(1 to array:size($array))[
  count($array(.)) = count($search) and
  every(for-each-pair(
    $array(.), $search, fn($a, $b) { exists(index-of($a, $b, $collation)) }
  ))
]

The first member in an array is at position 1, not position 0.

The result sequence is in ascending numeric order.

Notes

If $array is the empty array, or if no member in $array matches $search, then the function returns the empty sequence.

Examples

Expression:	`array:index-of([ 10, 20, 30, 30, 20, 10 ], 20)`
Result:	(2, 5)
Expression:	`array:index-of([ (), 1, (5, 6), (6, 7) ], (6, 7))`
Result:	4
Expression:	array:index-of( ["a", ("b", "C"), "d"], ("B", "c"), "http://www.w3.org/2005/xpath-functions/collation/html-ascii-case-insensitive" )
Result:	2
Expression:	array:index-of( [ '1', xs:untypedAtomic('1'), 1, current-date() ], '1' )
Result:	(1, 2)

19.1.14 array:index-where

Summary

Returns the position in an input array of members that match a supplied predicate.

Signature

`array:index-where`(
`$array`	`as` `array(*)`,
`$predicate`	`as` `function(item()*, xs:integer) as xs:boolean`
) `as` `xs:integer*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The result of the function is a sequence of integers, in monotonic ascending order, representing the 1-based positions in the input array of those members for which the supplied predicate function returns true.

More formally, the function returns the result of the expression:

index-of($input => array:for-each($predicate) => array:values(), true())

Examples

Expression:	`array:index-where([], boolean#1)`
Result:	()
Expression:	`array:index-where([0, (), 4, 9], boolean#1)`
Result:	(3, 4)
Expression:	array:index-where( array { 1 to 10 }, function {. mod 2 = 0 } )
Result:	(2, 4, 6, 8, 10)
Expression:	array:index-where( [ "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" ], contains(?, "r") )
Result:	(1, 2, 3, 4, 9, 10, 11, 12)
Expression:	array:index-where( [(1, 2, 3), (4, 5, 6), (7, 8)], function($m) { count($m) = 3 } )
Result:	(1, 2)
Expression:	array:index-where( [ 1, 8, 2, 7, 3 ], fn($member, $pos) { $member < 5 and $pos > 2 } )
Result:	(3, 5)

History

Approved 2022-12-13 for inclusion in 4.0 - issue #114

19.1.15 array:insert-before

Summary

Returns an array containing all the members of the supplied array, with one additional member at a specified position.

Signature

`array:insert-before`(
`$array`	`as` `array(*)`,
`$position`	`as` `xs:integer`,
`$member`	`as` `item()*`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function returns an array of size array:size($array) + 1 containing all members from $array whose position is less than $position, then a new member given by $member, and then all members from $array whose position is greater than or equal to $position. Positions are counted from 1.

More formally, except in error cases, the result is the value of the expression array:of-members(array:members($array) => fn:insert-before($position, map{'value':$member})).

Error Conditions

A dynamic error occurs [err:FOAY0001] if $position is not in the range 1 to array:size($array) + 1 inclusive.

Notes

Setting $position to 1 has the effect of prepending the new member at the start of the array. Setting $position to the value array:size($array) + 1 delivers the same result as array:append($array, $member).

Examples

Expression

Result

array:insert-before(
  ["a", "b", "c", "d"],
  3,
  ("x", "y")
)

["a", "b", ("x", "y"), "c", "d"]

array:insert-before(
  ["a", "b", "c", "d"],
  5,
  ("x", "y")
)

["a", "b", "c", "d", ("x", "y")]

array:insert-before(
  ["a", "b", "c", "d"],
  3,
  ["x", "y"]
)

["a", "b", ["x", "y"], "c", "d"]

History

First introduced in 3.1.Functionality unchanged in 4.0, but the specification has been formalized.

19.1.16 array:join

Summary

Concatenates the contents of several arrays into a single array.

Signature

`array:join`(
`$arrays`	`as` `array()`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function concatenates the members of several arrays into a single array.

More formally, the function returns the result of array:of-members($arrays ! array:members(.)).

Examples

Expression	Result
`array:join(())`	[ ]
`array:join([1, 2, 3])`	[1, 2, 3]
`array:join((["a", "b"], ["c", "d"]))`	["a", "b", "c", "d"]
`array:join((["a", "b"], ["c", "d"], [ ]))`	["a", "b", "c", "d"]
`array:join((["a", "b"], ["c", "d"], [["e", "f"]]))`	["a", "b", "c", "d", ["e", "f"]]

History

First introduced in 3.1.Functionality unchanged in 4.0, but the specification has been formalized.

19.1.17 array:members

Summary

Delivers the contents of an array as a sequence of value records.

Signature

`array:members`(
`$array`	`as` `array(*)`
) `as` `record(value as item())`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The members of the array are delivered as a sequence of value records. A value record is an item that encapsulates an arbitrary sequence $S: specifically it is a map comprising a single entry whose key is the xs:string value "value" and whose corresponding value is $S. The content encapsulated by a value record $V can be obtained using the expression $V?value.

Notes

This function is the inverse of array:of-members.

Examples

Expression:	`array:members([])`
Result:	()
Expression:	`array:members([1 to 5])?value`
Result:	(1, 2, 3, 4, 5)
Expression:	array:members([(1,1), (2,4), (3,9), (4,16), (5,25)]) ! sum(?value)
Result:	(2, 6, 12, 20, 30)
Expression:	let $array := [ "any array" ] return deep-equal( $array, array:of-members(array:members($array)) )
Result:	true()

History

Proposed for 4.0, see issues 29, 113, 314.

19.1.18 array:of-members

Summary

Constructs an array from the contents of a sequence of value records.

Signature

`array:of-members`(
`$input`	`as` `record(value as item())`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The input items must be value records. A value record is an item that encapsulates an arbitrary sequence $S: specifically it is a map comprising a single entry whose key is the xs:string value "value" and whose corresponding value is $S. The content encapsulated by a value record $V can be obtained using the expression $V?value.

Notes

This function is the inverse of array:members.

Examples

Expression	Result
`array:of-members(())`	[]
`array:of-members(map { 'value': (1 to 5) })`	[(1, 2, 3, 4, 5)]
`array:of-members((1 to 5) ! map { 'value': . })`	[1, 2, 3, 4, 5]
`array:of-members((1 to 5) ! map { 'value': (., .*.) })`	[(1,1), (2,4), (3,9), (4,16), (5,25)]

History

Proposed for 4.0, see issues 29, 113, 314.

19.1.19 array:put

Summary

Returns an array containing all the members of a supplied array, except for one member which is replaced with a new value.

Signature

`array:put`(
`$array`	`as` `array(*)`,
`$position`	`as` `xs:integer`,
`$member`	`as` `item()*`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the result is an array whose size is array:size($array), in which all members in positions other than $position are the same as the members in the corresponding position of $array, and the member in position $position is $member.

More formally, the result is the value of the expression $array => array:remove($position) => array:insert-before($position, $member).

Error Conditions

A dynamic error occurs [err:FOAY0001] if $position is not in the range 1 to array:size($array) inclusive.

This error will always occur if $array is empty.

Examples

Expression	Result
`array:put(["a", "b", "c"], 2, "d")`	["a", "d", "c"]
`array:put(["a", "b", "c"], 2, ("d", "e"))`	["a", ("d", "e"), "c"]
`array:put(["a"], 1, ["d", "e"])`	[["d", "e"]]

History

First introduced in 3.1.Unchanged in 4.0.

19.1.20 array:remove

Summary

Returns an array containing all the members of the supplied array, except for the members at specified positions.

Signature

`array:remove`(
`$array`	`as` `array(*)`,
`$positions`	`as` `xs:integer*`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function returns an array of size array:size($array) - fn:count(fn:distinct-values($positions)) containing all members from $array except the members whose position (counting from 1) is present in the sequence $positions. The order of the remaining members is preserved.

More formally, the result of the function, except in error cases, is given by the expression array:of-members(array:members($array) => fn:remove($positions)).

Error Conditions

A dynamic error is raised [err:FOAY0001] if any integer in $positions is not in the range 1 to array:size($array) inclusive. By implication, an error occurs if $array is empty, unless $positions is also empty.

Examples

Expression	Result
`array:remove(["a", "b", "c", "d"], 1)`	["b", "c", "d"]
`array:remove(["a", "b", "c", "d"], 2)`	["a", "c", "d" ]
`array:remove(["a"], 1)`	[ ]
`array:remove(["a", "b", "c", "d"], 1 to 3)`	["d"]
`array:remove(["a", "b", "c", "d"], ())`	["a", "b", "c", "d"]

History

First introduced in 3.1.Functionality unchanged in 4.0, but the specification has been formalized.

19.1.21 array:replace

Summary

Returns an array containing all the members of a supplied array, except for one member which is replaced with a new value, the new value being computed from the previous value.

Signature

`array:replace`(
`$array`	`as` `array(*)`,
`$position`	`as` `xs:integer`,
`$action`	`as` `function(item()) as item()`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

More formally, the result is the value of the expression $array => array:remove($position) => array:insert-before($position, $action($array($position))).

Error Conditions

A dynamic error occurs [err:FOAY0001] if $position is not in the range 1 to array:size($array) inclusive.

This error will always occur if $array is empty.

Examples

Expression Result

array:replace([10, 11, 12], 2, function { . + 10 })

[10, 21, 12]

array:replace(["a", "b", "c"], 2, concat(?, "x"))

["a", "bx", "c"]

array:replace([("a", "b"), ("c", "d")], 2, reverse#1)

[("a", "b"), ("d", "c")]

History

First introduced in 4.0.

19.1.22 array:reverse

Summary

Returns an array containing all the members of a supplied array, but in reverse order.

Signature

`array:reverse`(
`$array`	`as` `array(*)`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns the result of the expression: array:of-members(array:members($array) => fn:reverse())

Examples

Expression	Result
`array:reverse(["a", "b", "c", "d"])`	["d", "c", "b", "a"]
`array:reverse([("a", "b"), ("c", "d")])`	[("c", "d"), ("a", "b")]
`array:reverse([(1 to 5)])`	[(1, 2, 3, 4, 5)]
`array:reverse([])`	[]

History

First introduced in 3.1.Functionality unchanged in 4.0, but the specification has been formalized.

19.1.23 array:size

Summary

Returns the number of members in the supplied array.

Signature

`array:size`(
`$array`	`as` `array(*)`
) `as` `xs:integer`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Informally, the function returns the number of members in the array.

More formally, the function returns the value of count(array:members($array)).

Notes

Note that because an array is an item, the fn:count function when applied to an array always returns 1.

Examples

Expression	Result
`array:size(["a", "b", "c"])`	3
`array:size(["a", ["b", "c"]])`	2
`array:size([ ])`	0
`array:size([[ ]])`	1

19.1.24 array:slice

Summary

Returns an array containing selected members of a supplied input array based on their position.

Signature

`array:slice`(
`$array`	`as` `array(*)`,
`$start`	`as` `xs:integer?`	`:=` `()`,
`$end`	`as` `xs:integer?`	`:=` `()`,
`$step`	`as` `xs:integer?`	`:=` `()`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Returns the value of array:of-members(array:members($array) => fn:slice($start, $end, $step))

Notes

The function is formally defined by converting the array to a sequence, applying fn:slice to this sequence, and then converting the resulting sequence back to an array.

Note that unlike other operations on arrays, there are no out-of-bounds errors for inappropriate values of $start, $end, or $step.

Examples

Variables
let $in := ['a', 'b', 'c', 'd', 'e']

Expression	Result
`array:slice($in, start := 2, end := 4)`	["b", "c", "d"]
`array:slice($in, start := 2)`	["b", "c", "d", "e"]
`array:slice($in, end := 2)`	["a", "b"]
`array:slice($in, start := 3, end := 3)`	["c"]
`array:slice($in, start := 4, end := 3)`	["d", "c"]
`array:slice($in, start := 2, end := 5, step := 2)`	["b", "d"]
`array:slice($in, start := 5, end := 2, step := -2)`	["e", "c"]
`array:slice($in, start := 2, end := 5, step := -2)`	[]
`array:slice($in, start := 5, end := 2, step := 2)`	[]
`array:slice($in)`	["a", "b", "c", "d", "e"]
`array:slice($in, start := -1)`	["e"]
`array:slice($in, start := -3)`	["c", "d", "e"]
`array:slice($in, end := -2)`	["a", "b", "c", "d"]
`array:slice($in, start := 2, end := -2)`	["b", "c", "d"]
`array:slice($in, start := -2, end := 2)`	["d", "c", "b"]
`array:slice($in, start := -4, end := -2)`	["b", "c", "d"]
`array:slice($in, start := -2, end := -4)`	["d", "c", "b"]
`array:slice($in, start := -4, end := -2, step := 2)`	["b", "d"]
`array:slice($in, start := -2, end := -4, step := -2)`	["d", "b"]
`array:slice(["a", "b", "c", "d"], 0)`	["a", "b", "c", "d"]

History

Proposed for 4.0; not yet reviewed?.

19.1.25 array:sort

Summary

Sorts a supplied array, based on the value of a number of sort keys supplied as functions.

Signature

`array:sort`(
`$array`	`as` `array(*)`,
`$collations`	`as` `xs:string*`	`:=` `fn:default-collation()`,
`$keys`	`as` `(function(item()) as xs:anyAtomicType)*`	`:=` `fn:data#1`,
`$orders`	`as` `enum('ascending', 'descending')*`	`:=` `'ascending'`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-dependent·, and ·focus-independent·. It depends on collations.

Rules

The result of the function is an array that contains all the members from $input, typically in a different order, the order being defined by the supplied sort key definitions.

A sort key definition has three parts:

A sort key function, which is applied to each member in the input array to determine a sort key value.
A collation, which is used when comparing sort key values that are of type xs:string or xs:untypedAtomic.
An order direction, which is ascending or descending.

The $nth sort key definition (where $n counts from one (1)) is established as follows:

The sort key function is $keys[$n] otherwise data#1.
The collation is $collations[$n] otherwise $collations[last()] otherwise default-collation(). That is, it is the collation supplied in the corresponding item of the supplied $collations argument; or in its absence, the last entry in $collations; or if $collations is absent or empty, the default collation from the static context of the caller.
The order direction is $orders[$n] otherwise $orders[last()] otherwise "ascending". That is, it is "ascending" or "descending" according to the value of the corresponding item in the supplied $orders argument; or in its absence, the last entry in $orders; or if $orders is absent or empty, then "ascending".

The result of the function is defined by reference to the fn:sort function. Specifically, the result of the function is value of the expression:

array:of-members(
  sort(
    array:members($array),
    $collations,
    for $key in ($keys otherwise data#1)
    return function($member as record(value)) as xs:anyAtomicType* {
      $key($member?value)
    },
    $orders
  )
)

Error Conditions

If the set of computed sort keys contains values that are not comparable using the lt operator then the sort operation will fail with a type error ([err:XPTY0004]^XP).

Examples

Expression:	`array:sort([1, 4, 6, 5, 3])`
Result:	[1, 3, 4, 5, 6]
Expression:	`array:sort([1, 4, 4e0, 6, 5, 3], orders := "descending")`
Result:	[6, 5, 4, 4e0, 3, 1]
Expression:	`array:sort([1, -2, 5, 10, -10, 10, 8], (), abs#1)`
Result:	[1, -2, 5, 8, 10, -10, 10]
Expression:	`array:sort([[2, "i"], [1, "e"], [2, "g"], [1, "f"]])`
Result:	[[1, "e"], [1, "f"], [2, "g"], [2, "i"]]
Expression:	array:sort([[2, "i"], [1, "e"], [2, "g"], [1, "f"]], (), (array:get(?, 1), array:get(?, 2)), ("ascending", "descending"))
Result:	[[1, "f"], [1, "e"], [2, "i"], [2, "g"]]
To sort an array of strings `$in` using Swedish collation:
let $SWEDISH := "http://www.w3.org/2013/collation/UCA?lang=se" return array:sort($in, $SWEDISH)
To sort an array of maps representing employees, using last name as the major sort key and first name as the minor sort key, with the default collation:
array:sort($employees, (), function($emp) {$emp?name?last, $emp?name?first})

History

First introduced in 3.1.Changed in 4.0: Substantially revised in 4.0.

19.1.26 array:split

Summary

Delivers the contents of an array as a sequence of singleton arrays.

Signature

`array:split`(
`$array`	`as` `array(*)`
) `as` `array()`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The members of the array are delivered as a sequence of arrays. Each returned array encapsulates the value of a single array member.

Notes

The function call array:split($array) produces the same result as the expression for member $m in $array return [ $m ].

This function is the inverse of array:join.

Examples

Expression:	`array:split([])`
Result:	()
Expression:	`array:split([ () ])`
Result:	[ () ]
Expression:	`array:split([ 1 to 5 ])`
Result:	[ (1, 2, 3, 4, 5) ]
Expression:	array:split( array { 1 to 5 } )
Result:	[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ]
Expression:	array:split( [ (1,1), (2,4), (3,9), (4,16), (5,25) ] ) ! sum(.)
Result:	2, 6, 12, 20, 30
Expression:	let $array := [ "any array" ] return deep-equal( $array, array:join(array:split($array)) )
Result:	true()

19.1.27 array:subarray

Summary

Returns an array containing all members from a supplied array starting at a supplied position, up to a specified length.

Signature

`array:subarray`(
`$array`	`as` `array(*)`,
`$start`	`as` `xs:integer`,
`$length`	`as` `xs:integer?`	`:=` `()`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

Except in error cases, the two-argument version of the function returns the same result as the three-argument version when called with $length equal to the value of array:size($array) - $start + 1.

Setting the third argument to the empty sequence has the same effect as omitting the argument.

Except in error cases, the result of the three-argument version of the function is the value of the expression array:of-members(array:members($array) => fn:subsequence($start, $length)).

Error Conditions

A dynamic error is raised [err:FOAY0001] if $start is less than one or greater than array:size($array) + 1.

For the three-argument version of the function:

A dynamic error is raised [err:FOAY0002] if $length is less than zero.
A dynamic error is raised [err:FOAY0001] if $start + $length is greater than array:size($array) + 1.

Notes

The value of $start can be equal to array:size($array) + 1 provided that $length is either equal to zero or omitted. In this case the result will be an empty array.

Examples

Expression	Result
`array:subarray(["a", "b", "c", "d"], 2)`	["b", "c", "d"]
`array:subarray(["a", "b", "c", "d"], 5)`	[ ]
`array:subarray(["a", "b", "c", "d"], 2, 0)`	[ ]
`array:subarray(["a", "b", "c", "d"], 2, 1)`	["b"]
`array:subarray(["a", "b", "c", "d"], 2, 2)`	["b", "c"]
`array:subarray(["a", "b", "c", "d"], 5, 0)`	[ ]
`array:subarray([ ], 1, 0)`	[ ]

History

First introduced in 3.1.Functionality unchanged in 4.0, but the specification has been formalized.

19.1.28 array:tail

Summary

Returns an array containing all members except the first from a supplied array.

Signature

`array:tail`(
`$array`	`as` `array(*)`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns an array containing all members of the supplied array except the first, that is array:remove($array, 1).

Error Conditions

A dynamic error occurs [err:FOAY0001] if $array is empty.

Notes

If the supplied array contains exactly one member, the result will be an empty array.

Examples

Expression	Result
`array:tail([5, 6, 7, 8])`	[6, 7, 8]
`array:tail([5])`	[ ]

History

First introduced in 3.1.Unchanged in 4.0.

19.1.29 array:trunk

Summary

Returns an array containing all members except the last from a supplied array.

Signature

`array:trunk`(
`$array`	`as` `array(*)`
) `as` `array(*)`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function returns an array containing all members of the supplied array except the last, that is array:remove($array, array:size($array)).

Error Conditions

A dynamic error occurs [err:FOAY0001] if $array is empty.

Notes

If the supplied array contains exactly one member, the result will be an empty array.

Examples

Expression	Result
`array:trunk([5, 6, 7, 8])`	[5, 6, 7]
`array:trunk([5])`	[ ]

History

Proposed and accepted for 4.0, see issue 97

19.1.30 array:values

Summary

Returns a sequence with the members of an array.

Signature

`array:values`(
`$array`	`as` `array(*)`
) `as` `item()*`

Properties

This function is ·deterministic·, ·context-independent·, and ·focus-independent·.

Rules

The function concatenates the members of $array and returns them as a sequence. The values are returned in their original order. Arrays contained within members are returned unchanged.

The effect of the function is equivalent to $array?*.

Examples

Expression	Result
`array:values(array { "one", "two", "three" })`	("one", "two", "three")
`array:values([ (), 1, (2 to 4), [ 5 ] ])`	(1, 2, 3, 4, [ 5 ])

19.2 Additional Operations on Arrays

This section is non-normative.

The XPath language provides explicit syntax for certain operations on arrays. These constructs can also be specified in terms of functions primitives:

19.2.1 Singleton Arrays

array { $sequence } constructs an array whose members are the items in $sequence. Every member of this array will be a singleton item. This can be defined as array:join($sequence ! array { . }).
[E1, E2, E3, ..., En] constructs an array in which E1 is the first member, E2 is the second member, and so on. The result is equivalent to the expression array:join(([ E1 ], [ E2 ], ... [ En ])).
The lookup expression $array?* is equivalent to array:split($array)?*.
The lookup expression $array?$N, where $N is an integer within the bounds of the array, is equivalent to array:split($array)[$N]?*.
Similarly, applying the array as a function, $array($N), is also equivalent to array:split($array)[$N]?*

19.2.2 Value Maps

array { $sequence } constructs an array whose members are the items in $sequence. Every member of this array will be a singleton item. This can be defined as array:of-members($sequence ! map { 'value': . }).
[E1, E2, E3, ..., En] constructs an array in which E1 is the first member, E2 is the second member, and so on. The result is equivalent to the expression array:of-members((map { 'value': E1 }, map { 'value': E2 }, map { 'value': E3 }, ... map { 'value': En })).
The lookup expression $array?* is equivalent to array:members($array) ! ?value.
The lookup expression $array?$N, where $N is an integer within the bounds of the array, is equivalent to array:members($array)[$N]?value.
Similarly, applying the array as a function, $array($N), is also equivalent to array:members($array)[$N]?value

20 Constructor functions

Constructor functions are used to convert a supplied value to a given type, and the name of the function is the same as the name of the target type. This section describes constructor functions corresponding to the following types:

Simple types (atomic types, union types, and list types as defined in [XML Schema Part 2: Datatypes Second Edition]), which are present in the static context either because they appear in the in-scope schema types^XP40 or because they appear as [TERMDEF dt-named-item-types IN XP40]named item types.

These constructor functions always take a single argument.
Record tests defined as [TERMDEF dt-named-item-types IN XP40]named item types.

These take one argument for each named field of the record test. Constructor functions for record types are defined in 20.6 Constructor functions for named record tests.

Constructor functions are defined for all user-defined named simple types, and for most built-in atomic, list, and union types. The only named simple types that have no constructor function are those that have no instances other than instances of their derived types: specifically, xs:anySimpleType, xs:anyAtomicType, and xs:NOTATION.

20.1 Constructor functions for XML Schema built-in atomic types

Every built-in atomic type that is defined in [XML Schema Part 2: Datatypes Second Edition], except xs:anyAtomicType and xs:NOTATION, has an associated constructor function. The type xs:untypedAtomic, defined in Section 2.7 Schema Information ^DM31 and the two derived types xs:yearMonthDuration and xs:dayTimeDuration defined in Section 2.7 Schema Information ^DM31 also have associated constructor functions. Implementations may additionally provide a constructor functions for the new datatype xs:dateTimeStamp introduced in [Schema 1.1 Part 2].

A constructor function is not defined for xs:anyAtomicType as there are no atomic values with type annotation xs:anyAtomicType at runtime, although this can be a statically inferred type. A constructor function is not defined for xs:NOTATION since it is defined as an abstract type in [XML Schema Part 2: Datatypes Second Edition]. If the static context (See Section 2.1.1 Static Context ^XP31) contains a type derived from xs:NOTATION then a constructor function is defined for it. See 20.5 Constructor functions for user-defined atomic and union types.

The form of the constructor function for an atomic type eg:TYPE is:

`eg:TYPE`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `eg:TYPE?`

If $arg is the empty sequence, the empty sequence is returned. For example, the signature of the constructor function corresponding to the xs:unsignedInt type defined in [XML Schema Part 2: Datatypes Second Edition] is:

`xs:unsignedInt`(
`$arg`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:unsignedInt?`

Calling the constructor function xs:unsignedInt(12) returns the xs:unsignedInt value 12. Another call of that constructor function that returns the same xs:unsignedInt value is xs:unsignedInt("12"). The same result would also be returned if the constructor function were to be called with a node that had a typed value equal to the xs:unsignedInt 12. The standard features described in Section 2.4.2 Atomization ^XP31 would atomize the node to extract its typed value and then call the constructor with that value. If the value passed to a constructor is not in the lexical space of the datatype to be constructed, and cannot be converted to a value in the value space of the datatype under the rules in this specification, then an dynamic error is raised [err:FORG0001].

The semantics of the constructor function xs:TYPE(arg) are identical to the semantics of arg cast as xs:TYPE? . See 21 Casting.

If the argument to a constructor function is a literal, the result of the function may be evaluated statically; if an error is found during such evaluation, it may be reported as a static error.

Special rules apply to constructor functions for xs:QName and types derived from xs:QName and xs:NOTATION. See 20.2 Constructor functions for xs:QName and xs:NOTATION.

The argument is optional, and defaults to the context value (which will be atomized if necessary).

The following constructor functions for the built-in atomic types are supported:

`xs:string`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:string?`

`xs:boolean`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:boolean?`

`xs:decimal`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:decimal?`

`xs:float`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:float?`

Implementations should return negative zero for xs:float("-0.0E0"). But because [XML Schema Part 2: Datatypes Second Edition] does not distinguish between the values positive zero and negative zero, implementations may return positive zero in this case.

`xs:double`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:double?`

Implementations should return negative zero for xs:double("-0.0E0"). But because [XML Schema Part 2: Datatypes Second Edition] does not distinguish between the values positive zero and negative zero, implementations may return positive zero in this case.

`xs:duration`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:duration?`

`xs:dateTime`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:dateTime?`

`xs:time`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:time?`

`xs:date`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:date?`

`xs:gYearMonth`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:gYearMonth?`

`xs:gYear`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:gYear?`

`xs:gMonthDay`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:gMonthDay?`

`xs:gDay`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:gDay?`

`xs:gMonth`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:gMonth?`

`xs:hexBinary`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:hexBinary?`

`xs:base64Binary`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:base64Binary?`

`xs:anyURI`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:anyURI?`

`xs:QName`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:QName?`

See 20.2 Constructor functions for xs:QName and xs:NOTATION for special rules.

`xs:normalizedString`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:normalizedString?`

`xs:token`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:token?`

`xs:language`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:language?`

`xs:NMTOKEN`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:NMTOKEN?`

`xs:Name`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:Name?`

`xs:NCName`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:NCName?`

`xs:ID`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:ID?`

`xs:IDREF`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:IDREF?`

`xs:ENTITY`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:ENTITY?`

See 21.1.9 Casting to xs:ENTITY for rules related to constructing values of type xs:ENTITY and types derived from it.

`xs:integer`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:integer?`

`xs:nonPositiveInteger`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:nonPositiveInteger?`

`xs:negativeInteger`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:negativeInteger?`

`xs:long`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:long?`

`xs:int`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:int?`

`xs:short`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:short?`

`xs:byte`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:byte?`

`xs:nonNegativeInteger`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:nonNegativeInteger?`

`xs:unsignedLong`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:unsignedLong?`

`xs:unsignedInt`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:unsignedInt?`

`xs:unsignedShort`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:unsignedShort?`

`xs:unsignedByte`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:unsignedByte?`

`xs:positiveInteger`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:positiveInteger?`

`xs:yearMonthDuration`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:yearMonthDuration?`

`xs:dayTimeDuration`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:dayTimeDuration?`

`xs:untypedAtomic`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:untypedAtomic??`

`xs:dateTimeStamp`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:dateTimeStamp?`

Available only if the implementation supports XSD 1.1.

20.2 Constructor functions for xs:QName and xs:NOTATION

Special rules apply to constructor functions for the types xs:QName and xs:NOTATION, for two reasons:

Values cannot belong directly to the type xs:NOTATION, only to its subtypes.
The lexical representation of these types uses namespace prefixes, whose meaning is context-dependent.

These constraints result in the following rules:

There is no constructor function for xs:NOTATION. Constructors are defined, however, for xs:QName, for types derived or constructed from xs:QName, and for types derived or constructed from xs:NOTATION.
When converting from an xs:string, the prefix within the lexical xs:QName supplied as the argument is resolved to a namespace URI using the statically known namespaces from the static context. If the lexical xs:QName has no prefix, the namespace URI of the resulting expanded-QName is the default namespace for elements and types, taken from the static context. Components of the static context are defined in Section 2.1.1 Static Context ^XP31. A dynamic error is raised [err:FONS0004] if the prefix is not bound in the static context. As described in Section 2.1 Terminology ^DM31, the supplied prefix is retained as part of the expanded-QName value.

When a constructor function for a namespace-sensitive type is used as a literal function item or in a partial function application (for example, xs:QName#1 or xs:QName(?)) the namespace bindings that are relevant are those from the static context of the literal function item or partial function application. When a constructor function for a namespace-sensitive type is obtained by means of the fn:function-lookup function, the relevant namespace bindings are those from the static context of the call on fn:function-lookup.

Note:

When the supplied argument to the xs:QName constructor function is a node, the node is atomized in the usual way, and if the result is xs:untypedAtomic it is then converted as if a string had been supplied. The effect might not be what is desired. For example, given the attribute xsi:type="my:type", the expression xs:QName(@xsi:type) might fail on the grounds that the prefix my is undeclared. This is because the namespace bindings are taken from the static context (that is, from the query or stylesheet), and not from the source document containing the @xsi:type attribute. The solution to this problem is to use the function call resolve-QName(@xsi:type, .) instead.

20.3 Constructor functions for XML Schema built-in list types

Each of the three built-in list types defined in [XML Schema Part 2: Datatypes Second Edition], namely xs:NMTOKENS, xs:ENTITIES, and xs:IDREFS, has an associated constructor function.

The function signatures are as follows:

`xs:NMTOKENS`(
`$value`	`as` `xs:string?`	`:=` `.`
) `as` `xs:NMTOKEN*`

`xs:ENTITIES`(
`$value`	`as` `xs:string?`	`:=` `.`
) `as` `xs:ENTITY*`

`xs:IDREFS`(
`$value`	`as` `xs:string?`	`:=` `.`
) `as` `xs:IDREF*`

The semantics are equivalent to casting to the corresponding types from xs:string.

All three of these types have the facet minLength = 1 meaning that there must always be at least one item in the list. The return type, however, allows for the fact that when the argument to the function is an empty sequence, the result is an empty sequence.

Note:

In the case of atomic types, it is possible to use an expression such as xs:date(@date-of-birth) to convert an attribute value to an instance of xs:date, knowing that this will work both in the case where the attribute is already annotated as xs:date, and also in the case where it is xs:untypedAtomic. This approach does not work with list types, because it is not permitted to use a value of type xs:NMTOKEN* as input to the constructor function xs:NMTOKENS. Instead, it is necessary to use conditional logic that performs the conversion only in the case where the input is untyped: if (@x instance of attribute(*, xs:untypedAtomic)) then xs:NMTOKENS(@x) else data(@x)

20.4 Constructor functions for XML Schema built-in union types

There is a constructor function for the union type xs:numeric defined in [XQuery and XPath Data Model (XDM) 3.1]. The function signature is:

`xs:numeric`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:numeric?`

The semantics are determined by the rules in 21.3.5 Casting to union types. These rules have the effect that:

If the argument is an instance of xs:double, xs:float, or xs:decimal, then the result is an instance of the same primitive type, with the same value;
If the argument is an instance of xs:boolean, the result is the xs:double value 0.0e0 or 1.0e0;
If the argument is an instance of xs:string or xs:untypedAtomic, then:
1. If the value is in the lexical space of xs:double, the result will be the corresponding xs:double value;
2. Otherwise, a dynamic error [err:FORG0001] occurs;
Note:

The result will never be an instance of xs:float, xs:decimal, or xs:integer. This is because xs:double appears first in the list of member types of xs:numeric, and its lexical space subsumes the lexical space of the other numeric types. Thus, unlike XPath numeric literals, the result does not depend on the lexical form of the supplied value. The reason for this design choice is to retain compatibility with the function conversion rules: functions such as fn:abs and fn:round are declared to expect an instance of xs:numeric as their first or only argument, and compatibility with the function conversion rules defined in earlier versions of these specifications demands that when an untyped atomic value (or untyped node) is supplied as the argument, it is converted to an xs:double value even if its lexical form is that (say) of an integer.
In all other cases, a dynamic error [err:FORG0001] occurs.

In the case of an implementation that supports XSD 1.1, there is a constructor function associated with the built-in union type xs:error.

The function signature is as follows:

`xs:error`(
`$value`	`as` `xs:anyAtomicType?`	`:=` `.`
) `as` `xs:error?`

The semantics are equivalent to casting to the corresponding union type (see 21.3.5 Casting to union types).

Note:

Because xs:error has no member types, and therefore has an empty value space, casting will always fail with a dynamic error except in the case where the supplied argument is an empty sequence, in which case the result is also an empty sequence.

20.5 Constructor functions for user-defined atomic and union types

For every named user-defined simple type in the static context (See Section 2.1.1 Static Context ^XP31), there is a constructor function whose name is the same as the name of the typeand whose effect is to create a value of that type from the supplied argument. The rules for constructing user-defined types are defined in the same way as the rules for constructing built-in derived types defined in 20.1 Constructor functions for XML Schema built-in atomic types.

For named atomic types, the rules are the same as the rules for constructing built-in derived atomic types defined in 20.1 Constructor functions for XML Schema built-in atomic types. For a named atomic type T, the signature of the function takes the form T($value as xs:anyAtomicType? := .) as T?, and the semantics are the same as casting to derived types: see 21.3.1 Casting to derived types..

For named union types, the rules follow the same principles as the rules for constructing built-in union types defined in 20.4 Constructor functions for XML Schema built-in union types. For a named union type U, the signature of the function takes the form U($value as xs:anyAtomicType? := .) as U?, and the semantics are the same as casting to union types: see 21.3.5 Casting to union types.

For named list types, the rules follow the same principles as the rules for constructing built-in list types defined in 20.3 Constructor functions for XML Schema built-in list types. For a named list type L, where the item type of L is I, the signature of the function takes the form L($value as xs:string? := .) as I*, and the semantics are the same as casting to list types: see 21.3.6 Casting to list types.

Constructor functions are available both for named types defined in an imported schema (that is, named simple types in the in-scope schema types^XP40), and for types defined by means of [TERMDEF dt-item-type-aliases IN XP40]. Specifically, named enumeration types follow the same rules as schema types derived by restricting xs:string, and named local union types follow the same rules as union types defined in a schema.

Special rules apply to constructor functions for namespace-sensitive types, that is, atomic types derived from xs:QName and xs:NOTATION, list types that have a namespace-sensitive item type, and union types that have a namespace-sensitive member type. See 20.2 Constructor functions for xs:QName and xs:NOTATION.

Example: Using a Constructor Function for a User-Defined Atomic Type

Consider a situation where the static context contains an atomic type called hatSize defined in a schema whose target namespace is bound to the prefix eg. In such a case the following constructor function is available to users:

`eg:hatSize`(
`$value`	`as` `xs:anyAtomicType`
) `as` `my:hatSize?`

The resulting function may be used in an expression such as eg:hatSize("10½").

In the case of an atomic type A, the return type of the function is A?, reflecting the fact that the result will be an empty sequence if the input is an empty sequence. For a union or list type, the return type of the function is specified only as xs:anyAtomicType*. Implementations performing static type checking will often be able to compute a more specific result type. For example, if the target type is a list type whose item type is the atomic type A, the result will always be an instance of A*; if the target type is a pure union type U then the result will always be an instance of U?. In general, however, applications needing interoperable behavior on implementations that do strict static type checking will need to use a treat as expression to assert the specific type of the result.

Note:

To construct an instance of a user-defined type that is not in a namespace, it is possible to use an EQName (for example Q{}hatsize(17)). Alternatives are to use a cast expression (17 cast as hatsize) or (if the host language allows it) to undeclare the default function namespace.

20.6 Constructor functions for named record tests

For every named item type in the static context (See Section 2.1.1 Static Context ^XP31) whose expansion is a record test, there is a constructor function whose name is the same as the name of the type, and whose parameters correspond to the fields defined in the record test.

For example, if there is a named item type with the XQuery definition:

declare item type my:location 
    as record(latitude as xs:double, longitude as xs:double)

then there will be a function definition equivalent to:

declare function my:location (
        $latitude as xs:double,
        $longitude as xs:double) as my:location {
    map{'latitude':$latitude, 'longitude':$longitude}
}

Equivalently using XSLT syntax, if there is a named item type with the XSLT definition:

<xsl:item-type name="my:location"
    as="record(latitude as xs:double, longitude as xs:double)"/>

then there will be a function definition equivalent to:

<xsl:function name="my:location" as="my:location">
    <xsl:param name="latitude" as="xs:double"/>
    <xsl:param name="longitude" as="xs:double"/>
    <xsl:map>
        <xsl:map-entry key="'latitude'" select="$latitude"/>
        <xsl:map-entry key="'longitude'" select="$longitude"/>
    </xsl:map>
</xsl:function>

The rules defining the relationship of the function definition to the record test are as follows:

The name of the function is the same as the name of the named item type. A static error occurs if this clashes with the name and arity of other function definitions in the static context.
For every named field in the record test, in order, there is is one parameter defined as follows:
1. If the name of the field is an NCName, then the name of the parameter is the name of the field.
2. Otherwise, the name of the parameter is argNZ, where arg is the literal string "arg", N is the ordinal position of the field, counting from 1 (one), and Z is an implementation-defined suffix, added only when needed to make the parameter name unique.
3. The declared type of the parameter is the same as the declared type of the field, but if the field is declared optional, then the occurrence indicator is adjusted to ? or * if needed to make the empty sequence a valid value for the parameter.
4. If the field is optional and if all subsequent fields are optional, then the parameter is declared as optional with a default value of () (the empty sequence). In all other cases the parameter is declared as required.
It is immaterial whether the record test is extensible; the constructor function cannot be used to create entries in the resulting map other than entries corresponding to named fields.
The return type of the constructor function is the record test (with no occurrence indicator).
The body of the function constructs a map having one entry for each mandatory field in the record test, and one entry for each optional field in the record test for which an actual value other than the empty sequence is supplied in the arguments of the function call. The key of the entry is the field name as an instance of xs:string, and the corresponding value is the value supplied in the arguments to the constructor function call, after applying the coercion rules.

Example: Record constructor with optional fields

Consider the record test (in XQuery syntax):

declare item type p:person as record(
    "1st-title"? as xs:string,
    "2nd-title"? as xs:string,
    first as xs:string,
    middle? as xs:string,
    last as xs:string,
    suffix? as xs:string,
    *)

This will result in an implicit function declaration equivalent to:

declare function p:person (
    $arg1 as xs:string?,
    $arg2 as xs:string?,
    $first as xs:string,
    $middle as xs:string?,
    $last as xs:string,
    $suffix as xs:string? := ()) as p:person {
        let $m := map{},
            $m := if (exists($arg1)) then map:put($m, "1st-title", $arg1) else $m,
            $m := if (exists($arg2)) then map:put($m, "2nd-title", $arg2) else $m,
            $m := map:put($m, "first", $first),
            $m := if (exists($middle)) then map:put($m, "middle", $middle) else $m,
            $m := map:put($m, "last", $last),
            $m := if (exists($suffix)) then map:put($m, "suffix", $suffix) else $m
        return $m
    };

21 Casting

Constructor functions and cast expressions accept an expression and return a value of a given type. They both convert a source value, SV, of a source type, ST, to a target value, TV, of the given target type, TT, with identical semantics and different syntax. The name of the constructor function is the same as the name of the built-in [XML Schema Part 2: Datatypes Second Edition] datatype or the datatype defined in Section 2.7 Schema Information ^DM31 of [XQuery and XPath Data Model (XDM) 3.1] (see 20.1 Constructor functions for XML Schema built-in atomic types) or the user-derived datatype (see 20.5 Constructor functions for user-defined atomic and union types) that is the target for the conversion, and the semantics are exactly the same as for a cast expression; for example, xs:date("2003-01-01") means exactly the same as "2003-01-01" cast as xs:date?.

The cast expression takes a type name to indicate the target type of the conversion. See Section 3.14.2 Cast ^XP31. If the type name allows the empty sequence and the expression to be cast is the empty sequence, the empty sequence is returned. If the type name does not allow the empty sequence and the expression to be cast is the empty sequence, a type error is raised [err:XPTY0004]^XP.

Where the argument to a cast is a literal, the result of the function may be evaluated statically; if an error is encountered during such evaluation, it may be reported as a static error.

The general rules for casting from primitive types to primitive types are defined in 21.1 Casting from primitive types to primitive types, and subsections describe the rules for specific target types. The general rules for casting from xs:string (and xs:untypedAtomic) follow in 21.2 Casting from xs:string and xs:untypedAtomic. Casting to non-primitive types, including atomic types derived by resctriction, union types, and list types, is described in 21.3 Casting involving non-primitive types. Casting from derived types is defined in 21.3.2 Casting from derived types to parent types, 21.3.3 Casting within a branch of the type hierarchy and 21.3.4 Casting across the type hierarchy.

[Definition] Throughout this section (21 Casting), the term primitive type means either one of the 19 primitive types defined in [XML Schema Part 2: Datatypes Second Edition], or one of the types xs:untypedAtomic, xs:integer, xs:yearMonthDuration and xs:dayTimeDuration; and where the text refers to types derived from a particular primitive type T, the reference is to types for which T is the nearest ancestor-or-self primitive type in the type hierarchy.

When casting from xs:string or xs:untypedAtomic the semantics in 21.2 Casting from xs:string and xs:untypedAtomic apply, regardless of target type.

21.1 Casting from primitive types to primitive types

This section defines casting between ·primitive types· (specifically, the 19 primitive types defined in [XML Schema Part 2: Datatypes Second Edition] as well as xs:untypedAtomic, xs:integer and the two derived types of xs:duration: xs:yearMonthDuration and xs:dayTimeDuration which are treated as primitive types in this section. The type conversions that are supported between primitive atomic types are indicated in the table below; casts between other (non-primitive) types are defined in terms of these primitives.

In this table, there is a row for each ·primitive type· acting as the source of the conversion and there is a column for each ·primitive type· acting as the target of the conversion. The intersections of rows and columns contain one of three characters: Y indicates that a conversion from values of the type to which the row applies to the type to which the column applies is supported; N indicates that there are no supported conversions from values of the type to which the row applies to the type to which the column applies; and M indicates that a conversion from values of the type to which the row applies to the type to which the column applies may succeed for some values in the value space and fail for others.

[XML Schema Part 2: Datatypes Second Edition] defines xs:NOTATION as an abstract type. Thus, casting to xs:NOTATION from any other type including xs:NOTATION is not permitted and raises a static error [err:XPST0080]^XP. However, casting from one subtype of xs:NOTATION to another subtype of xs:NOTATION is permitted.

Casting is not supported to or from xs:anySimpleType. Thus, there is no row or column for this type in the table below. For any node that has not been validated or has been validated as xs:anySimpleType, the typed value of the node is an atomic value of type xs:untypedAtomic. There are no atomic values with the type annotation xs:anySimpleType at runtime. Casting to xs:anySimpleType is not permitted and raises a static error: [err:XPST0080]^XP.

Similarly, casting is not supported to or from xs:anyAtomicType and will raise a static error: [err:XPST0080]^XP. There are no atomic values with the type annotation xs:anyAtomicType at runtime, although this can be a statically inferred type.

If casting is attempted from an ST to a TT for which casting is not supported, as defined in the table below, a type error is raised [err:XPTY0004]^XP.

In the following table, the columns and rows are identified by short codes that identify simple types as follows:

uA = xs:untypedAtomic
aURI = xs:anyURI
b64 = xs:base64Binary
bool = xs:boolean
dat = xs:date
gDay = xs:gDay
dbl = xs:double
dec = xs:decimal
dT = xs:dateTime
dTD = xs:dayTimeDuration
dur = xs:duration
flt = xs:float
hxB = xs:hexBinary
gMD = xs:gMonthDay
gMon = xs:gMonth
int = xs:integer
NOT = xs:NOTATION
QN = xs:QName
str = xs:string
tim = xs:time
gYM = xs:gYearMonth
yMD = xs:yearMonthDuration
gYr = xs:gYear

In the following table, the notation “S\T” indicates that the source (“S”) of the conversion is indicated in the column below the notation and that the target (“T”) is indicated in the row to the right of the notation.

S\T	uA	str	flt	dbl	dec	int	dur	yMD	dTD	dT	tim	dat	gYM	gYr	gMD	gDay	gMon	bool	b64	hxB	aURI	QN	NOT
uA	Y	Y	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M
str	Y	Y	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M	M
flt	Y	Y	Y	Y	M	M	N	N	N	N	N	N	N	N	N	N	N	Y	N	N	N	N	N
dbl	Y	Y	Y	Y	M	M	N	N	N	N	N	N	N	N	N	N	N	Y	N	N	N	N	N
dec	Y	Y	Y	Y	Y	Y	N	N	N	N	N	N	N	N	N	N	N	Y	N	N	N	N	N
int	Y	Y	Y	Y	Y	Y	N	N	N	N	N	N	N	N	N	N	N	Y	N	N	N	N	N
dur	Y	Y	N	N	N	N	Y	Y	Y	N	N	N	N	N	N	N	N	N	N	N	N	N	N
yMD	Y	Y	N	N	N	N	Y	Y	Y	N	N	N	N	N	N	N	N	N	N	N	N	N	N
dTD	Y	Y	N	N	N	N	Y	Y	Y	N	N	N	N	N	N	N	N	N	N	N	N	N	N
dT	Y	Y	N	N	N	N	N	N	N	Y	Y	Y	Y	Y	Y	Y	Y	N	N	N	N	N	N
tim	Y	Y	N	N	N	N	N	N	N	N	Y	N	N	N	N	N	N	N	N	N	N	N	N
dat	Y	Y	N	N	N	N	N	N	N	Y	N	Y	Y	Y	Y	Y	Y	N	N	N	N	N	N
gYM	Y	Y	N	N	N	N	N	N	N	N	N	N	Y	N	N	N	N	N	N	N	N	N	N
gYr	Y	Y	N	N	N	N	N	N	N	N	N	N	N	Y	N	N	N	N	N	N	N	N	N
gMD	Y	Y	N	N	N	N	N	N	N	N	N	N	N	N	Y	N	N	N	N	N	N	N	N
gDay	Y	Y	N	N	N	N	N	N	N	N	N	N	N	N	N	Y	N	N	N	N	N	N	N
gMon	Y	Y	N	N	N	N	N	N	N	N	N	N	N	N	N	N	Y	N	N	N	N	N	N
bool	Y	Y	Y	Y	Y	Y	N	N	N	N	N	N	N	N	N	N	N	Y	N	N	N	N	N
b64	Y	Y	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	Y	Y	N	N	N
hxB	Y	Y	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	Y	Y	N	N	N
aURI	Y	Y	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	Y	N	N
QN	Y	Y	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	Y	M
NOT	Y	Y	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	N	Y	M

21.1.1 Casting to xs:string and xs:untypedAtomic

Casting is permitted from any ·primitive type· to the ·primitive types· xs:string and xs:untypedAtomic.

When a value of any simple type is cast as xs:string, the derivation of the xs:string value TV depends on the ST and on the SV, as follows.

If ST is xs:string or a type derived from xs:string, TV is SV.
If ST is xs:anyURI, the type conversion is performed without escaping any characters.
If ST is xs:QName or xs:NOTATION:
- if the qualified name has a prefix, then TV is the concatenation of the prefix of SV, a single colon (:), and the local name of SV.
- otherwise TV is the local-name.
If ST is a numeric type, the following rules apply:
- If ST is xs:integer, TV is the canonical lexical representation of SV as defined in [XML Schema Part 2: Datatypes Second Edition]. There is no decimal point.
- If ST is xs:decimal, then:
  - If SV is in the value space of xs:integer, that is, if there are no significant digits after the decimal point, then the value is converted from an xs:decimal to an xs:integer and the resulting xs:integer is converted to an xs:string using the rule above.
  - Otherwise, the canonical lexical representation of SV is returned, as defined in [XML Schema Part 2: Datatypes Second Edition].
- If ST is xs:float or xs:double, then:
  - TV will be an xs:string in the lexical space of xs:double or xs:float that when converted to an xs:double or xs:float under the rules of 21.2 Casting from xs:string and xs:untypedAtomic produces a value that is equal to SV, or is NaN if SV is NaN. In addition, TV must satisfy the constraints in the following sub-bullets.
    - If SV has an absolute value that is greater than or equal to 0.000001 (one millionth) and less than 1000000 (one million), then the value is converted to an xs:decimal and the resulting xs:decimal is converted to an xs:string according to the rules above, as though using an implementation of xs:decimal that imposes no limits on the totalDigits or fractionDigits facets.
    - If SV has the value positive or negative zero, TV is "0" or "-0" respectively.
    - If SV is positive or negative infinity, TV is the string "INF" or "-INF" respectively.
    - In other cases, the result consists of a mantissa, which has the lexical form of an xs:decimal, followed by the letter "E", followed by an exponent which has the lexical form of an xs:integer. Leading zeroes and "+" signs are prohibited in the exponent. For the mantissa, there must be a decimal point, and there must be exactly one digit before the decimal point, which must be non-zero. The "+" sign is prohibited. There must be at least one digit after the decimal point. Apart from this mandatory digit, trailing zero digits are prohibited.
  Note:
  
  The above rules allow more than one representation of the same value. For example, the xs:float value whose exact decimal representation is 1.26743223E15 might be represented by any of the strings "1.26743223E15", "1.26743222E15" or "1.26743224E15" (inter alia). It is implementation-dependent which of these representations is chosen.
If ST is xs:dateTime, xs:date or xs:time, TV is the local value. The components of TV are individually cast to xs:string using the functions described in [casting-to-datetimes] and the results are concatenated together. The year component is cast to xs:string using eg:convertYearToString. The month, day, hour and minute components are cast to xs:string using eg:convertTo2CharString. The second component is cast to xs:string using eg:convertSecondsToString. The timezone component, if present, is cast to xs:string using eg:convertTZtoString.

Note that the hours component of the resulting string will never be "24". Midnight is always represented as "00:00:00".
If ST is xs:yearMonthDuration or xs:dayTimeDuration, TV is the canonical representation of SV as defined in [Schema 1.1 Part 2].
If ST is xs:duration then let SYM be SV cast as xs:yearMonthDuration, and let SDT be SV cast as xs:dayTimeDuration; Now, let the next intermediate value, TYM, be SYM cast as TT , and let TDT be SDT cast as TT . If TYM is "P0M", then TV is TDT. Otherwise, TYM and TDT are merged according to the following rules:
1. If TDT is "PT0S", then TV is TYM.
2. Otherwise, TV is the concatenation of all the characters in TYM and all the characters except the first "P" and the optional negative sign in TDT.
In all other cases, TV is the [XML Schema Part 2: Datatypes Second Edition] canonical representation of SV. For datatypes that do not have a canonical lexical representation defined an ·implementation-dependent· canonical representation may be used.

To cast as xs:untypedAtomic the value is cast as xs:string, as described above, and the type annotation changed to xs:untypedAtomic.

Note:

The string representations of numeric values are backwards compatible with XPath 1.0 except for the special values positive and negative infinity, negative zero and values outside the range 1.0e-6 to 1.0e+6.

21.1.2 Casting to numeric types

21.1.2.1 Casting to xs:float

When a value of any simple type is cast as xs:float, the xs:float TV is derived from the ST and the SV as follows:

If ST is xs:float, then TV is SV and the conversion is complete.
If ST is xs:double, then TV is obtained as follows:
- if SV is the xs:double value INF, -INF, NaN, positive zero, or negative zero, then TV is the xs:float value INF, -INF, NaN, positive zero, or negative zero respectively.
- otherwise, SV can be expressed in the form m × 2^e where the mantissa m and exponent e are signed xs:integers whose value range is defined in [XML Schema Part 2: Datatypes Second Edition], and the following rules apply:
  - if m (the mantissa of SV) is outside the permitted range for the mantissa of an xs:float value (-2^24-1 to +2^24-1), then it is divided by 2^N where N is the lowest positive xs:integer that brings the result of the division within the permitted range, and the exponent e is increased by N. This is integer division (in effect, the binary value of the mantissa is truncated on the right). Let M be the mantissa and E the exponent after this adjustment.
  - if E exceeds 104 (the maximum exponent value in the value space of xs:float) then TV is the xs:float value INF or -INF depending on the sign of M.
  - if E is less than -149 (the minimum exponent value in the value space of xs:float) then TV is the xs:float value positive or negative zero depending on the sign of M
  - otherwise, TV is the xs:float value M × 2^E.
If ST is xs:decimal, or xs:integer, then TV is xs:float( SV cast as xs:string) and the conversion is complete.
If ST is xs:boolean, SV is converted to 1.0E0 if SV is true and to 0.0E0 if SV is false and the conversion is complete.
If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.

Note:

XSD 1.1 adds the value +INF to the lexical space, as an alternative to INF. XSD 1.1 also adds negative zero to the value space.

Note:

Implementations should return negative zero for xs:float("-0.0E0"). But because [XML Schema Part 2: Datatypes Second Edition] does not distinguish between the values positive zero and negative zero. Implementations may return positive zero in this case.

21.1.2.2 Casting to xs:double

When a value of any simple type is cast as xs:double, the xs:double value TV is derived from the ST and the SV as follows:

If ST is xs:double, then TV is SV and the conversion is complete.
If ST is xs:float or a type derived from xs:float, then TV is obtained as follows:
- if SV is the xs:float value INF, -INF, NaN, positive zero, or negative zero, then TV is the xs:double value INF, -INF, NaN, positive zero, or negative zero respectively.
- otherwise, SV can be expressed in the form m × 2^e where the mantissa m and exponent e are signed xs:integer values whose value range is defined in [XML Schema Part 2: Datatypes Second Edition], and TV is the xs:double value m × 2^e.
If ST is xs:decimal or xs:integer, then TV is xs:double( SV cast as xs:string) and the conversion is complete.
If ST is xs:boolean, SV is converted to 1.0E0 if SV is true and to 0.0E0 if SV is false and the conversion is complete.
If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.

Note:

XSD 1.1 adds the value +INF to the lexical space, as an alternative to INF. XSD 1.1 also adds negative zero to the value space.

Note:

Implementations should return negative zero for xs:double("-0.0E0"). But because [XML Schema Part 2: Datatypes Second Edition] does not distinguish between the values positive zero and negative zero. Implementations may return positive zero in this case.

21.1.2.3 Casting to xs:decimal

When a value of any simple type is cast as xs:decimal, the xs:decimal value TV is derived from ST and SV as follows:

If ST is xs:decimal, xs:integer or a type derived from them, then TV is SV, converted to an xs:decimal value if need be, and the conversion is complete.
If ST is xs:float or xs:double, then TV is the xs:decimal value, within the set of xs:decimal values that the implementation is capable of representing, that is numerically closest to SV. If two values are equally close, then the one that is closest to zero is chosen. If SV is too large to be accommodated as an xs:decimal, (see [XML Schema Part 2: Datatypes Second Edition] for ·implementation-defined· limits on numeric values) a dynamic error is raised [err:FOCA0001]. If SV is one of the special xs:float or xs:double values NaN, INF, or -INF, a dynamic error is raised [err:FOCA0002].
If ST is xs:boolean, SV is converted to 1.0 if SV is 1 or true and to 0.0 if SV is 0 or false and the conversion is complete.
If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.

21.1.2.4 Casting to xs:integer

When a value of any simple type is cast as xs:integer, the xs:integer value TV is derived from ST and SV as follows:

If ST is xs:integer, or a type derived from xs:integer, then TV is SV, converted to an xs:integer value if need be, and the conversion is complete.
If ST is xs:decimal, xs:float or xs:double, then TV is SV with the fractional part discarded and the value converted to xs:integer. Thus, casting 3.1456 returns 3 and -17.89 returns -17. Casting 3.124E1 returns 31. If SV is too large to be accommodated as an integer, (see [XML Schema Part 2: Datatypes Second Edition] for ·implementation-defined· limits on numeric values) a dynamic error is raised [err:FOCA0003]. If SV is one of the special xs:float or xs:double values NaN, INF, or -INF, a dynamic error is raised [err:FOCA0002].
If ST is xs:boolean, SV is converted to 1 if SV is 1 or true and to 0 if SV is 0 or false and the conversion is complete.
If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.

21.1.3 Casting to duration types

When a value of type xs:untypedAtomic, xs:string, a type derived from xs:string, xs:yearMonthDuration or xs:dayTimeDuration is cast as xs:duration, xs:yearMonthDuration or xs:dayTimeDuration, TV is derived from ST and SV as follows:

If ST is the same as TT, then TV is SV.
If ST is xs:duration, or a type derived from xs:duration, but not xs:dayTimeDuration or a type derived from xs:dayTimeDuration, and TT is xs:yearMonthDuration, then TV is derived from SV by removing the day, hour, minute and second components from SV.
If ST is xs:duration, or a type derived from duration, but not xs:yearMonthDuration or a type derived from xs:yearMonthDuration, and TT is xs:dayTimeDuration, then TV is derived from SV by removing the year and month components from SV.
If ST is xs:yearMonthDuration or xs:dayTimeDuration, and TT is xs:duration, then TV is derived from SV as defined in 21.3.2 Casting from derived types to parent types.
If ST is xs:yearMonthDuration and TT is xs:dayTimeDuration, the cast is permitted and returns a xs:dayTimeDuration with value 0.0 seconds.
If ST is xs:dayTimeDuration and TT is xs:yearMonthDuration, the cast is permitted and returns a xs:yearMonthDuration with value 0 months.
If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.

Note that casting from xs:duration to xs:yearMonthDuration or xs:dayTimeDuration loses information. To avoid this, users can cast the xs:duration value to both an xs:yearMonthDuration and an xs:dayTimeDuration and work with both values.

21.1.4 Casting to date and time types

In several situations, casting to date and time types requires the extraction of a component from SV or from the result of fn:current-dateTime and converting it to an xs:string. These conversions must follow certain rules. For example, converting an xs:integer year value requires converting to an xs:string with four or more characters, preceded by a minus sign if the value is negative.

This document defines four functions to perform these conversions. These functions are for illustrative purposes only and make no recommendations as to style or efficiency. References to these functions from the following text are not normative.

The arguments to these functions come from functions defined in this document. Thus, the functions below assume that they are correct and do no range checking on them.

declare function eg:convertYearToString($year as xs:integer) as xs:string
{
   let $plusMinus := if ($year >= 0) then "" else "-"
   let $yearString := abs($year) cast as xs:string
   let $length := string-length($yearString)
   return
     if ($length = 1)  then concat($plusMinus, "000", $yearString)
     else
     if ($length = 2)  then concat($plusMinus, "00", $yearString)
       else
       if ($length = 3)  then concat($plusMinus, "0", $yearString)
       else concat($plusMinus, $yearString)
}

declare function eg:convertTo2CharString($value as xs:integer) as xs:string
{
   let $string := $value cast as xs:string
   return 
     if (string-length($string) = 1) then concat("0", $string)
     else $string
}

declare function eg:convertSecondsToString($seconds as xs:decimal) as xs:string
{
   let $string := $seconds cast as xs:string
   let $intLength := string-length(($seconds cast as xs:integer) cast as xs:string)
   return 
     if ($intLength = 1) then concat("0", $string)
     else $string
}

declare function eg:convertTZtoString($tz as xs:dayTimeDuration?) as xs:string
{
   if (empty($tz)) 
     then ""
   else if ($tz eq xs:dayTimeDuration('PT0S'))
     then "Z"
   else 
     let $tzh := hours-from-duration($tz)
     let $tzm := minutes-from-duration($tz)
     let $plusMinus := if ($tzh >= 0) then "+" else "-"
     let $tzhString := eg:convertTo2CharString(abs($tzh))
     let $tzmString := eg:convertTo2CharString(abs($tzm))
     return concat($plusMinus, $tzhString, ":", $tzmString)
}

Conversion from ·primitive types· to date and time types follows the rules below.

When a value of any primitive type is cast as xs:dateTime, the xs:dateTime value TV is derived from ST and SV as follows:
- If ST is xs:dateTime, then TV is SV.
- If ST is xs:date, then let SYR be eg:convertYearToString( year-from-date( SV )), let SMO be eg:convertTo2CharString( month-from-date( SV )), let SDA be eg:convertTo2CharString( day-from-date( SV )) and let STZ be eg:convertTZtoString( timezone-from-date( SV )); TV is xs:dateTime( concat( SYR , '-', SMO , '-', SDA , 'T00:00:00 ', STZ ) ).
- If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.
When a value of any primitive type is cast as xs:time, the xs:time value TV is derived from ST and SV as follows:
- If ST is xs:time, then TV is SV.
- If ST is xs:dateTime, then TV is xs:time( concat( eg:convertTo2CharString( hours-from-dateTime( SV )), ':', eg:convertTo2CharString( minutes-from-dateTime( SV )), ':', eg:convertSecondsToString( seconds-from-dateTime( SV )), eg:convertTZtoString( timezone-from-dateTime( SV )) )).
- If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.
When a value of any primitive type is cast as xs:date, the xs:date value TV is derived from ST and SV as follows:
- If ST is xs:date, then TV is SV.
- If ST is xs:dateTime, then let SYR be eg:convertYearToString( year-from-dateTime( SV )), let SMO be eg:convertTo2CharString( month-from-dateTime( SV )), let SDA be eg:convertTo2CharString( day-from-dateTime( SV )) and let STZ be eg:convertTZtoString(timezone-from-dateTime( SV )); TV is xs:date( concat( SYR , '-', SMO , '-', SDA, STZ ) ).
- If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.
When a value of any primitive type is cast as xs:gYearMonth, the xs:gYearMonth value TV is derived from ST and SV as follows:
- If ST is xs:gYearMonth, then TV is SV.
- If ST is xs:dateTime, then let SYR be eg:convertYearToString( year-from-dateTime( SV )), let SMO be eg:convertTo2CharString( month-from-dateTime( SV )) and let STZ be eg:convertTZtoString( timezone-from-dateTime( SV )); TV is xs:gYearMonth( concat( SYR , '-', SMO, STZ ) ).
- If ST is xs:date, then let SYR be eg:convertYearToString( year-from-date( SV )), let SMO be eg:convertTo2CharString( month-from-date( SV )) and let STZ be eg:convertTZtoString( timezone-from-date( SV )); TV is xs:gYearMonth( concat( SYR , '-', SMO, STZ ) ).
- If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.
When a value of any primitive type is cast as xs:gYear, the xs:gYear value TV is derived from ST and SV as follows:
- If ST is xs:gYear, then TV is SV.
- If ST is xs:dateTime, let SYR be eg:convertYearToString( year-from-dateTime( SV )) and let STZ be eg:convertTZtoString( timezone-from-dateTime( SV )); TV is xs:gYear(concat( SYR, STZ )).
- If ST is xs:date, let SYR be eg:convertYearToString( year-from-date( SV )); and let STZ be eg:convertTZtoString( timezone-from-date( SV )); TV is xs:gYear(concat( SYR, STZ )).
- If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.
When a value of any primitive type is cast as xs:gMonthDay, the xs:gMonthDay value TV is derived from ST and SV as follows:
- If ST is xs:gMonthDay, then TV is SV.
- If ST is xs:dateTime, then let SMO be eg:convertTo2CharString( month-from-dateTime( SV )), let SDA be eg:convertTo2CharString( day-from-dateTime( SV )) and let STZ be eg:convertTZtoString( timezone-from-dateTime( SV )); TV is xs:gYearMonth( concat( '--', SMO '-', SDA, STZ ) ).
- If ST is xs:date, then let SMO be eg:convertTo2CharString( month-from-date( SV )), let SDA be eg:convertTo2CharString( day-from-date( SV )) and let STZ be eg:convertTZtoString( timezone-from-date( SV )); TV is xs:gYearMonth( concat( '--', SMO , '-', SDA, STZ ) ).
- If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.
When a value of any primitive type is cast as xs:gDay, the xs:gDay value TV is derived from ST and SV as follows:
- If ST is xs:gDay, then TV is SV.
- If ST is xs:dateTime, then let SDA be eg:convertTo2CharString( day-from-dateTime( SV )) and let STZ be eg:convertTZtoString( timezone-from-dateTime( SV )); TV is xs:gDay( concat( '---', SDA, STZ )).
- If ST is xs:date, then let SDA be eg:convertTo2CharString( day-from-date( SV )) and let STZ be eg:convertTZtoString( timezone-from-date( SV )); TV is xs:gDay( concat( '---', SDA, STZ )).
- If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.
When a value of any primitive type is cast as xs:gMonth, the xs:gMonth value TV is derived from ST and SV as follows:
- If ST is xs:gMonth, then TV is SV.
- If ST is xs:dateTime, then let SMO be eg:convertTo2CharString( month-from-dateTime( SV )) and let STZ be eg:convertTZtoString( timezone-from-dateTime( SV )); TV is xs:gMonth( concat( '--', SMO, STZ )).
- If ST is xs:date, then let SMO be eg:convertTo2CharString( month-from-date( SV )) and let STZ be eg:convertTZtoString( timezone-from-date( SV )); TV is xs:gMonth( concat( '--', SMO, STZ )).
- If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.

21.1.5 Casting to xs:boolean

When a value of any ·primitive type· is cast as xs:boolean, the xs:boolean value TV is derived from ST and SV as follows:

If ST is xs:boolean, then TV is SV.
If ST is xs:float, xs:double, xs:decimal or xs:integer and SV is 0, +0, -0, 0.0, 0.0E0 or NaN, then TV is false.
If ST is xs:float, xs:double, xs:decimal or xs:integer and SV is not one of the above values, then TV is true.
If ST is xs:untypedAtomic or xs:string, see 21.2 Casting from xs:string and xs:untypedAtomic.

21.1.6 Casting to xs:base64Binary and xs:hexBinary

Values of type xs:base64Binary can be cast as xs:hexBinary and vice versa, since the two types have the same value space. Casting to xs:base64Binary and xs:hexBinary is also supported from the same type and from xs:untypedAtomic, xs:string and subtypes of xs:string using [XML Schema Part 2: Datatypes Second Edition] semantics.

21.1.7 Casting to xs:anyURI

Casting to xs:anyURI is supported only from the same type, xs:untypedAtomic or xs:string.

When a value of any ·primitive type· is cast as xs:anyURI, the xs:anyURI value TV is derived from the ST and SV as follows:

If ST is xs:untypedAtomic or xs:string see 21.2 Casting from xs:string and xs:untypedAtomic.

21.1.8 Casting to xs:QName and xs:NOTATION

Casting from xs:string or xs:untypedAtomic to xs:QName or xs:NOTATION is described in 21.2 Casting from xs:string and xs:untypedAtomic.

It is also possible to cast from xs:NOTATION to xs:QName, or from xs:QName to any type derived by restriction from xs:NOTATION. (Casting to xs:NOTATION itself is not allowed, because xs:NOTATION is an abstract type.) The resulting xs:QName or xs:NOTATION has the same prefix, local name, and namespace URI parts as the supplied value.

Note:

See 20.2 Constructor functions for xs:QName and xs:NOTATION for a discussion of how the combination of atomization and casting might not produce the desired effect.

21.1.9 Casting to xs:ENTITY

[XML Schema Part 2: Datatypes Second Edition] says that “The value space of ENTITY is the set of all strings that match the NCName production ... and have been declared as an unparsed entity in a document type definition.” However, [XSL Transformations (XSLT) Version 4.0] and [XQuery 4.1: An XML Query Language] do not check that constructed values of type xs:ENTITY match declared unparsed entities. Thus, this rule is relaxed in this specification and, in casting to xs:ENTITY and types derived from it, no check is made that the values correspond to declared unparsed entities.

21.2 Casting from xs:string and xs:untypedAtomic

This section applies when the supplied value SV is an instance of xs:string or xs:untypedAtomic, including types derived from these by restriction. If the value is xs:untypedAtomic, it is treated in exactly the same way as a string containing the same sequence of characters.

The supplied string is mapped to a typed value of the target type as defined in [XML Schema Part 2: Datatypes Second Edition]. Whitespace normalization is applied as indicated by the whiteSpace facet for the datatype. The resulting whitespace-normalized string must be a valid lexical form for the datatype. The semantics of casting follow the rules of XML Schema validation. For example, "13" cast as xs:unsignedInt returns the xs:unsignedInt typed value 13. This could also be written xs:unsignedInt("13").

The target type can be any simple type other than an abstract type. Specifically, it can be a type whose variety is atomic, union, or list. In each case the effect of casting to the target type is the same as constructing an element with the supplied value as its content, validating the element using the target type as the governing type, and atomizing the element to obtain its typed value.

When the target type is a derived type that is restricted by a pattern facet, the lexical form is first checked against the pattern before further casting is attempted (See 21.3.1 Casting to derived types). If the lexical form does not conform to the pattern, a dynamic error [err:FORG0001] is raised.

For example, consider a user-defined type my:boolean which is derived by restriction from xs:boolean and specifies the pattern facet value="0|1". The expression "true" cast as my:boolean would fail with a dynamic error [err:FORG0001].

Facets other than pattern are checked after the conversion. For example if there is a user-defined datatype called my:height defined as a restriction of xs:integer with the facet <maxInclusive value="84"/>, then the expression "100" cast as my:height would fail with a dynamic error [err:FORG0001].

Casting to the types xs:NOTATION, xs:anySimpleType, or xs:anyAtomicType is not permitted because these types are abstract (they have no immediate instances).

Special rules apply when casting to namespace-sensitive types. The types xs:QName and xs:NOTATION are namespace-sensitive. Any type derived by restriction from a namespace-sensitive type is itself namespace-sensitive, as is any union type having a namespace-sensitive type among its members, and any list type having a namespace-sensitive type as its item type. For details, see 20.2 Constructor functions for xs:QName and xs:NOTATION.

Note:

This version of the specification allows casting between xs:QName and xs:NOTATION in either direction; this was not permitted in the previous Recommendation. This version also removes the rule that only a string literal (rather than a dynamic string) may be cast to an xs:QName

When casting to a numeric type:

If the value is too large or too small to be accurately represented by the implementation, it is handled as an overflow or underflow as defined in 4.2 Arithmetic operators on numeric values.
If the target type is xs:float or xs:double, the string -0 (and equivalents such as -0.0 or -000) should be converted to the value negative zero. However, if the implementation is reliant on an implementation of XML Schema 1.0 in which negative zero is not part of the value space for these types, these lexical forms may be converted to positive zero.

In casting to xs:decimal or to a type derived from xs:decimal, if the value is not too large or too small but nevertheless cannot be represented accurately with the number of decimal digits available to the implementation, the implementation may round to the nearest representable value or may raise a dynamic error [err:FOCA0006]. The choice of rounding algorithm and the choice between rounding and error behavior and is ·implementation-defined·.

In casting to xs:date, xs:dateTime, xs:gYear, or xs:gYearMonth (or types derived from these), if the value is too large or too small to be represented by the implementation, a dynamic error [err:FODT0001] is raised.

In casting to a duration value, if the value is too large or too small to be represented by the implementation, a dynamic error [err:FODT0002] is raised.

For xs:anyURI, the extent to which an implementation validates the lexical form of xs:anyURI is ·implementation-dependent·.

If the cast fails for any other reason, a dynamic error [err:FORG0001] is raised.

21.3 Casting involving non-primitive types

Casting from xs:string and xs:untypedAtomic to any other type (primitive or non-primitive) has been described in 21.2 Casting from xs:string and xs:untypedAtomic. This section defines how other casts to non-primitive types operate, including casting to types derived by restriction, to union types, and to list types.

Note:

A non-primitive type here means any type that is not a ·primitive type· according to the extended definition used in 21 Casting.

21.3.1 Casting to derived types

Casting a value to a derived type can be separated into four cases. In these rules:

The types xs:untypedAtomic, xs:integer, xs:yearMonthDuration, and xs:dayTimeDuration are treated as primitive types (alongside the 19 primitive types defined in XSD).
For any atomic type T, let P(T) denote the most specific primitive type such that itemType-subtype(T, P(T)) is true.

The rules are then:

When ST is the same type as TT: this case always succeeds, returning SV unchanged.
When itemType-subtype(ST, TT) is true: This case is described in 21.3.2 Casting from derived types to parent types.
When P(ST) is the same type as P(TT): This case is described in 21.3.3 Casting within a branch of the type hierarchy.
Otherwise (P(ST) is not the same type as P(TT)): This case is described in 21.3.4 Casting across the type hierarchy.

21.3.2 Casting from derived types to parent types

It is always possible to cast an atomic value A to a type T if the relation A instance of T is true, provided that T is not an abstract type.

For example, it is possible to cast an xs:unsignedShort to an xs:unsignedInt, to an xs:integer, to an xs:decimal, or to a union type whose member types are xs:integer and xs:double.

Since the value space of the original type is a subset of the value space of the target type, such a cast is always successful.

For the expression A instance of T to be true, T must be either an atomic type, or a union type that has no constraining facets. It cannot be a list type, nor a union type derived by restriction from another union type, nor a union type that has a list type among its member types.

The result will have the same value as the original, but will have a new type annotation:

If T is an atomic type, then the type annotation of the result is T.
If T is a union type, then the type of the result is an atomic type M such that M is one of the atomic types in the transitive membership of the union type T and A instance of M is true; if there is more than one type M that satisfies these conditions (which could happen, for example, if T is the union of two overlapping types such as xs:int and xs:positiveInteger) then the first one is used, taking the member types in the order in which they appear within the definition of the union type.

21.3.3 Casting within a branch of the type hierarchy

It is possible to cast an SV to a TT if the type of the SV and the TT type are both derived by restriction (directly or indirectly) from the same ·primitive type·, provided that the supplied value conforms to the constraints implied by the facets of the target type. This includes the case where the target type is derived from the type of the supplied value, as well as the case where the type of the supplied value is derived from the target type. For example, an instance of xs:byte can be cast as xs:unsignedShort, provided the value is not negative.

If the value does not conform to the facets defined for the target type, then a dynamic error is raised [err:FORG0001]. See [XML Schema Part 2: Datatypes Second Edition]. In the case of the pattern facet (which applies to the lexical space rather than the value space), the pattern is tested against the canonical lexical representation of the value, as defined for the source type (or the result of casting the value to an xs:string, in the case of types that have no canonical lexical representation defined for them).

Note that this will cause casts to fail if the pattern excludes the canonical lexical representation of the source type. For example, if the type my:distance is defined as a restriction of xs:decimal with a pattern that requires two digits after the decimal point, casting of an xs:integer to my:distance will always fail, because the canonical representation of an xs:integer does not conform to this pattern.

In some cases, casting from a parent type to a derived type requires special rules. See 21.1.3 Casting to duration types for rules regarding casting to xs:yearMonthDuration and xs:dayTimeDuration. See 21.1.9 Casting to xs:ENTITY, below, for casting to xs:ENTITY and types derived from it.

21.3.4 Casting across the type hierarchy

When the ST and the TT are derived, directly or indirectly, from different ·primitive types·, this is called casting across the type hierarchy. Casting across the type hierarchy is logically equivalent to three separate steps performed in order. Errors can occur in either of the latter two steps.

Cast the SV, up the hierarchy, to the ·primitive type· of the source, as described in 21.3.2 Casting from derived types to parent types.
1. If SV is an instance of xs:string or xs:untypedAtomic, check its value against the pattern facet of TT, and raise a dynamic error [err:FORG0001] if the check fails.
Cast the value to the ·primitive type· of TT, as described in 21.1 Casting from primitive types to primitive types.
- If TT is derived from xs:NOTATION, assume for the purposes of this rule that casting to xs:NOTATION succeeds.
Cast the value down to the TT, as described in 21.3.3 Casting within a branch of the type hierarchy

21.3.5 Casting to union types

If the target type of a cast expression (or a constructor function) is a type with variety union, the supplied value must be one of the following:

A value of type xs:string or xs:untypedAtomic. This case follows the general rules for casting from strings, and has already been described in 21.2 Casting from xs:string and xs:untypedAtomic.

If the union type has a pattern facet, the pattern is tested against the supplied value after whitespace normalization, using the whiteSpace normalization rules of the member datatype against which validation succeeds.
A value that is an instance of one of the atomic types in the transitive membership of the union type, and of the union type itself. This case has already been described in 21.3.2 Casting from derived types to parent types

This situation only applies when the value is an instance of the union type, which means it will never apply when the union is derived by facet-based restriction from another union type.
A value that is castable to one or more of the atomic types in the transitive membership of the union type (in the sense that the castable as operator returns true).

In this case the supplied value is cast to each atomic type in the transitive membership of the union type in turn (in the order in which the member types appear in the declaration) until one of these casts is successful; if none of them is successful, a dynamic error occurs [err:FORG0001]. If the union type has constraining facets then the resulting value must satisfy these facets, otherwise a dynamic error occurs [err:FORG0001].

If the union type has a pattern facet, the pattern is tested against the canonical representation of the result value.

Only the atomic types in the transitive membership of the union type are considered. The union type may have list types in its transitive membership, but (unless the supplied value is of type xs:string or xs:untypedAtomic, in which case the rules in 21.2 Casting from xs:string and xs:untypedAtomic apply), any list types in the membership are effectively ignored.

If more than one of these conditions applies, then the casting is done according to the rules for the first condition that applies.

If none of these conditions applies, the cast fails with a dynamic error [err:FORG0001].

Example: consider a type U whose member types are xs:integer and xs:date.

The expression "123" cast as U returns the xs:integer value 123.
The expression current-date() cast as U returns the current date as an instance of xs:date.
The expression 23.1 cast as U returns the xs:integer value 23.

Example: consider a type V whose member types are xs:short and xs:negativeInteger.

The expression "-123" cast as V returns the xs:short value -123.
The expression "-100000" cast as V returns the xs:negativeInteger value -100000.
The expression 93.7 cast as V returns the xs:short value 93.
The expression "93.7" cast as V raises a dynamic error [err:FORG0001] on the grounds that the string "93.7" is not in the lexical space of the union type.

Example: consider a type W that is derived from the above type V by restriction, with a pattern facet of -?\d\d.

The expression "12" cast as V returns the xs:short value 12.
The expression "123" cast as V raises an dynamic error [err:FORG0001] on the grounds that the string "123" does not match the pattern facet.

21.3.6 Casting to list types

If the target type of a cast expression (or a constructor function) is a type with variety list, the supplied value must be of type xs:string or xs:untypedAtomic. The rules follow the general principle for all casts from xs:string outlined in 21.2 Casting from xs:string and xs:untypedAtomic.

If the supplied value is not of type xs:string or xs:untypedAtomic, a type error is raised [err:XPTY0004]^XP.

The semantics of the operation are consistent with validation: that is, the effect of casting a string S to a list type L is the same as constructing an element or attribute node whose string value is S, validating it using L as the governing type, and atomizing the resulting node. The result will always be either failure, or a sequence of zero or more atomic values each of which is an instance of the item type of L (or if the item type of L is a union type, an instance of one of the atomic types in its transitive membership).

If the item type of the list type is namespace-sensitive, then the namespace bindings in the static context will be used to resolve any namespace prefix, in the same way as when the target type is xs:QName.

If the list type has a pattern facet, the pattern must match the supplied value after collapsing whitespace (an operation equivalent to the use of the fn:normalize-space function).

For example, the expression cast "A B C D" as xs:NMTOKENS produces a sequence of four xs:NMTOKEN values, ("A", "B", "C", "D").

For example, given a user-defined type my:coordinates defined as a list of xs:integer with the facet <xs:length value="2"/>, the expression my:coordinates("2 -1") will return a sequence of two xs:integer values (2, -1), while the expression my:coordinates("1 2 3") will result in a dynamic error because the length of the list does not conform to the length facet. The expression my:coordinates("1.0 3.0") will also fail because the strings 1.0 and 3.0 are not in the lexical space of xs:integer.

Function name	Availability
fn:accumulator-after	XSLT 3.0 only
fn:accumulator-before	XSLT 3.0 only
fn:available-system-properties	XSLT 3.0 only
fn:collation-key	Common to XSLT 3.0 and XPath 3.1
fn:copy-of	XSLT 3.0 only
fn:current	XSLT 1.0, 2.0, and 3.0
fn:current-group	XSLT 2.0 and 3.0
fn:current-grouping-key	XSLT 2.0 and 3.0
fn:current-merge-group	XSLT 3.0 only
fn:current-merge-key	XSLT 3.0 only
fn:current-output-uri	XSLT 3.0 only
fn:document	XSLT 1.0, 2.0, and 3.0
fn:element-available	XSLT 1.0, 2.0, and 3.0
fn:format-date	XSLT 2.0; migrated to XPath 3.0 and 3.1
fn:format-dateTime	XSLT 2.0; migrated to XPath 3.0 and 3.1
fn:format-number	XSLT 1.0 and 2.0; migrated to XPath 3.0 and 3.1
fn:format-time	XSLT 2.0; migrated to XPath 3.0 and 3.1
fn:function-available	XSLT 1.0, 2.0, and 3.0
fn:generate-id	XSLT 1.0 and 2.0; migrated to XPath 3.0 and 3.1
fn:json-to-xml	Common to XSLT 3.0 and XPath 3.1
fn:key	XSLT 1.0, 2.0, and 3.0
fn:regex-group	XSLT 2.0 and 3.0
fn:snapshot	XSLT 3.0 only
fn:stream-available	XSLT 3.0 only
fn:system-property	XSLT 1.0, 2.0, and 3.0
fn:type-available	XSLT 2.0 and 3.0
fn:unparsed-entity-public-id	XSLT 2.0 and 3.0
fn:unparsed-entity-uri	XSLT 1.0, 2.0, and 3.0
fn:unparsed-text	XSLT 2.0; migrated to XPath 3.0 and 3.1
fn:xml-to-json	Common to XSLT 3.0 and XPath 3.1
map:contains	Common to XSLT 3.0 and XPath 3.1
map:entry	Common to XSLT 3.0 and XPath 3.1
map:find	Common to XSLT 3.0 and XPath 3.1
map:for-each	Common to XSLT 3.0 and XPath 3.1
map:get	Common to XSLT 3.0 and XPath 3.1
map:keys	Common to XSLT 3.0 and XPath 3.1
map:merge	Common to XSLT 3.0 and XPath 3.1
map:put	Common to XSLT 3.0 and XPath 3.1
map:remove	Common to XSLT 3.0 and XPath 3.1
map:size	Common to XSLT 3.0 and XPath 3.1

XPath and XQuery Functions and Operators 4.0

W3C Editor's Draft 5 March 2024

Abstract

Status of this Document

1 Introduction

1.1 Operators

1.2 Conformance

1.3 Namespaces and prefixes

1.4 Function overloading

1.5 Function signatures and descriptions

1.6 Options

1.7 Type System

1.7.1 Item Types

1.7.2 Schema Type Hierarchy

1.7.3 Atomic Type Hierarchy

1.8 Terminology

1.8.1 Strings, characters, and codepoints

1.8.2 Namespaces and URIs

1.8.3 Conformance terminology

1.8.4 Properties of functions

2 Accessors

2.1 fn:node-name

2.2 fn:nilled

2.3 fn:string

2.4 fn:data

2.5 fn:base-uri

2.6 fn:document-uri

3 Errors and diagnostics

3.1 Raising errors

3.1.1 fn:error

3.2 Diagnostic tracing

3.2.1 fn:trace

3.2.2 fn:message

3.2.3 fn:stack-trace

4 Functions and operators on numerics

4.1 Numeric types

4.2 Arithmetic operators on numeric values

4.2.1 op:numeric-add

4.2.2 op:numeric-subtract

4.2.3 op:numeric-multiply

4.2.4 op:numeric-divide

4.2.5 op:numeric-integer-divide

4.2.6 op:numeric-mod

4.2.7 op:numeric-unary-plus

4.2.8 op:numeric-unary-minus

4.3 Comparison operators on numeric values

4.3.1 op:numeric-equal

4.3.2 op:numeric-less-than

4.4 Functions on numeric values

4.4.1 fn:abs

4.4.2 fn:ceiling

4.4.3 fn:floor

4.4.4 fn:round

4.4.5 fn:round-half-to-even

4.4.6 fn:is-NaN

4.5 Parsing numbers

4.5.1 fn:number

4.5.2 fn:parse-integer

4.6 Formatting integers

4.6.1 fn:format-integer

4.7 Formatting numbers

4.7.1 Defining a decimal format

4.7.2 fn:format-number

4.7.3 Syntax of the picture string

4.7.4 Analyzing the picture string

4.7.5 Formatting the number

4.8 Trigonometric and exponential functions

4.8.1 math:pi

4.8.2 math:exp

4.8.3 math:exp10

4.8.4 math:log

4.8.5 math:log10

4.8.6 math:pow

4.8.7 math:sqrt

4.8.8 math:sin

4.8.9 math:cos

4.8.10 math:tan

4.8.11 math:asin

4.8.12 math:acos

4.8.13 math:atan