View Old View New View Both View Only Previous Next

This draft contains only sections that have differences from the version that it modified.

W3C

XQuery 4.0: An XML Query Language

W3C Editor's Draft 30 January2 February 2026

This version:
https://qt4cg.org/specifications/xquery-40/
Most recent version of XQuery:
https://qt4cg.org/specifications/xquery-40/
Most recent Recommendation of XQuery:
https://www.w3.org/TR/2017/REC-xquery-31-20170321/
Editor:
Michael Kay, Saxonica <http://www.saxonica.com/>

This document is also available in these non-normative formats: XML.


Abstract

XML is a versatile markup language, capable of labeling the information content of diverse data sources, including structured and semi-structured documents, relational databases, and object repositories. A query language that uses the structure of XML intelligently can express queries across all these kinds of data, whether physically stored in XML or viewed as XML via middleware. This specification describes a query language called XQuery, which is designed to be broadly applicable across many types of XML data sources.

A list of changes made since XQuery 3.1 can be found in J Change Log.

Status of this Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document.

This document is a working draft developed and maintained by a W3C Community Group, the XQuery and XSLT Extensions Community Group unofficially known as QT4CG (where "QT" denotes Query and Transformation). This draft is work in progress and should not be considered either stable or complete. Standard W3C copyright and patent conditions apply.

The community group welcomes comments on the specification. Comments are best submitted as issues on the group's GitHub repository.

As the Community Group moves towards publishing dated, stable drafts, some features that the group thinks may likely be removed or substantially changed are marked “at risk” in their changes section. In this draft:

The community group maintains two extensive test suites, one oriented to XQuery and XPath, the other to XSLT. These can be found at qt4tests and xslt40-test respectively. New tests, or suggestions for correcting existing tests, are welcome. The test suites include extensive metadata describing the conditions for applicability of each test case as well as the expected results. They do not include any test drivers for executing the tests: each implementation is expected to provide its own test driver.

Dedication

The publications of this community group are dedicated to our co-chair, Michael Sperberg-McQueen (1954–2024).


2 Basics

2.1 Terminology

Changes in 4.0 (next | previous)

  1. The EBNF operators ++ and ** have been introduced, for more concise representation of sequences using a character such as "," as a separator. The notation is borrowed from Invisible XML.  [Issue 1366 PR 1498]

The basic building block of XQuery 4.0 is the expression, which is a string of [Unicode] characters; the version of Unicode to be used is implementation-defined. The language provides several kinds of expressions which may be constructed from keywords, symbols, and operands. In general, the operands of an expression are other expressions. XQuery 4.0 allows expressions to be nested with full generality. (However, unlike a pure functional language, it does not allow variable substitution if the variable declaration contains construction of new nodes.)

Note:

This specification contains no assumptions or requirements regarding the character set encoding of strings of [Unicode] characters.

Like XML, XQuery 4.0 is a case-sensitive language. Keywords in XQuery 4.0 use lower-case characters and are not reserved—that is, names in XQuery 4.0 expressions are allowed to be the same as language keywords, except for certain unprefixed function-names listed in A.4 Reserved Function Names.

In this specification the phrases must, must not, should, should not, may, required, and recommended, when used in normative text and rendered in small capitals, are to be interpreted as described in [RFC2119].

Certain aspects of language processing are described in this specification as implementation-defined or implementation-dependent.

  • [Definition: Implementation-defined indicates an aspect that may differ between implementations, but must be specified by the implementer for each particular implementation.]

  • [Definition: Implementation-dependent indicates an aspect that may differ between implementations, is not specified by this or any W3C specification, and is not required to be specified by the implementer for any particular implementation.]

2.1.3 Values

Changes in 4.0 (next | previous)

  1. The term atomic value has been replaced by atomic item.   [Issue 1337 PR 1361 2 August 2024]

  2. The terms XNode and JNode are introduced; the existing term node remains in use as a synonym for XNode where the context does not specify otherwise.   [Issue 2025 PR 2031 13 June 2025]

[Definition: In the data model, a value is always a sequence.]

[Definition: A sequence is an ordered collection of zero or more items.]

[Definition: An item is either an atomic item, a node, or a function item.]

[Definition: An atomic item is a value in the value space of an atomic type, as defined in [XML Schema 1.0] or [XML Schema 1.1].]

[Definition: An XNode is an instance of one of the node kinds defined in [XDM 4.0] section 7.1 XML Nodes.] Each XNode has a unique node identity, a typed value, and a string value. In addition, some XNodes have a name. The typed value of an XNode is a sequence of zero or more atomic items. The string value of an XNode is a value of type xs:string. The name of an XNode is a value of type xs:QName.

[Definition: Except where the context indicates otherwise, the term node is used as a synonym for XNode.]

[Definition: A function item is an item that can be called using a dynamic function call.]

Maps (see 4.14.1 Maps) and arrays (see 4.14.2 Arrays) are specific kinds of function items.

[Definition: A sequence containing exactly one item is called a singleton.] An item is identical to a singleton sequence containing that item. Sequences are never nested—for example, combining the values 1, (2, 3), and ( ) into a single sequence results in the sequence (1, 2, 3). [Definition: A sequence containing zero items is called an empty sequence.]

[Definition: A sequence containing zero items is called an empty sequence.]

[Definition: The term XDM instance is used, synonymously with the term value, to denote an unconstrained sequence of items.]

2.3 External Resources and Security

Changes in 4.0 (next | previous)

  1. This section (“External Resources and Security”) is new.  [Issue 2047 PR 2213 23 October 2025]

The XPath, XQuery, and XSLT languages provide a number of capabilities to access external resources. These include:

  • Functions such as doc, doc-available, unparsed-text, unparsed-text-lines, unparsed-text-available, collectionuri-collection, and unparsed-binary, and in XSLT, the document function and the xsl:source-document and xsl:merge instructions.

  • Static inclusion of code using import module in XQuery, or xsl:include, xsl:import, and xsl:use-package in XSLT.

  • Dynamic inclusion and execution of external code using the functions transform and load-xquery-module, and in XSLT, the xsl:evaluate instruction.

  • The ability to write to external resources using the xsl:result-document instruction in XSLT, or the put function in the XQuery Update Facility.

  • The ability to invoke arbitrary user-defined external functions (called extension functions in XSLT).

  • The ability to invoke vendor-defined external/extension functions; a notable example being the EXPath File library.

  • Access to environment variables and system properties using functions such as environment-variable, available-environment-variables, and (in XSLT) system-property.

  • Static inclusion of XSD schemas and schema documents using import schemain XQuery or xsl:import-schema in XSLT, or indirectly using xs:import, xs:include, xs:redefine, or xs:override in XSD schema documents.

  • Dynamic loading of XSD schema documents (directly or indirectly) using the xsd-validator function.

  • The ability to parse XML or HTML documents that contain references to external entities, for example by using the parse-xml and parse-html functions.

  • The ability to parse XML documents in a way that causes other external resources to be fetched, for example by activating XInclude, or by performing XSD validation using xsi:schema-location.

  • Implicit access to third-party libraries supporting (for example) collations or localization.

[Definition: The static context includes a boolean property called trusted that determines whether external resources are available.] This may take the following values:

  1. false: No external resources are available other than resources explicitly made available by the caller through some trusted implementation-defined mechanism.

    [Definition: ]Code executing with trusted set to false is said to be untrusted.]

  2. true: Trusted code has access to all the resources available to its immediate caller.

The functions transform and load-xquery-module, and the XSLT instruction xsl:evaluate, have an option allowing the trust level of the executed code to be set:

  1. If trusted is set to true, the invoked code executes with the same trust level as its caller.

  2. If trusted is set to false, the invoked code is not able to access any external resources other than resources explicitly made available using an implementation defined mechanism under the control of the caller.

Some resources, such as XML documents, may themselves contain references to other resources. For example, an XML document may reference external entities (including an external DTD). External entity expansion is recognized as a known security risk. Functions that invoke XML parsing (such as parse-xml, doc, or collection) therefore have a trusted option indicating whether the document being parsed is trusted to access external entities. Such access is allowed only if (a) the trusted option is set to true, or (b) access to the external entity in question is explicitly enabled by the caller.

Note:

The term explicitly enabled is not intended to mean that every resource to which access is permitted must be individually listed. The mechanism for enabling access might provide access to a class of resources (for example, all resources accessible using the HTTPS protocol, or all resources within the containing XML database having particular access permissions). The mechanism might also take account of other criteria, for example it might impose limits on the size or other characteristics of the resources accessed.

It is recommended that any external API used to invoke XPath, XQuery, or XSLT processing should similarly offer the ability to indicate whether the code being executed is trusted.

In the interests of security, the default for these options is false. However, for backwards compatibility reasons, processors may provide an option whereby a trusted user can change the default.

In general, when an application requests access to an external resource which is not available because the application is untrusted, the processor should behave in the same way as if the resource did not exist. However, the processor may choose to disclose in its diagnostics why the request was unsuccessful.

A processor may (but is not required to) limit an application’s consumption of resources such as CPU cycles and memory when the application is untrusted.

[Definition: The term available documents refers (TODO: for the time being) to the set of XML documents that an application is able to access by URI.]

G Glossary (Non-Normative)

absolute path expression

An absolute path expression is an instance of the production AbsolutePathExpr: it consists of either (a) the operator / followed by zero or more operands separated by / or // operators, or (b) the operator // followed by one or more operands separated by / or // operators.

and expression

An and expression is a non-trivial instance of the production AndExpr.

anonymous function

An anonymous function is a function item with no name. Anonymous functions may be created, for example, by evaluating an inline function expression or by partial function application.

application function

Application functions are function definitions written in a host language such as XQuery or XSLT whose syntax and semantics are defined in this family of specifications. Their behavior (including the rules determining the static and dynamic context) follows the rules for such functions in the relevant host language specification.

argument expression

An argument to a function call is either an argument expression or an ArgumentPlaceholder (?); in both cases it may either be supplied positionally, or identified by a name (called a keyword).

arity range

A function definition has an arity range, which is a range of consecutive non-negative integers. If the function definition has M required parameters and N optional parameters, then its arity range is from M to M+N inclusive.

array

An array is a function item that associates a set of positions, represented as positive integer keys, with values.

associated value

The value associated with a given key is called the associated value of the key.

atomic item

An atomic item is a value in the value space of an atomic type, as defined in [XML Schema 1.0] or [XML Schema 1.1].

atomic type

An atomic type is a simple schema type whose {variety}XS11-1 is atomic.

atomization

Atomization of a sequence is defined as the result of invoking the fn:data function, as defined in [Functions and Operators 4.0] section 12.1.6 fn:data.

available documents

The term available documents refers (TODO: for the time being) to the set of XML documents that an application is able to access by URI.

axis step

An axis step is an instance of the production AxisStep: it is an expression that returns a sequence of GNodes that are reachable from a starting GNode via a specified axis. An axis step has three parts: an axis, which defines the direction of movement for the step, a node test, which selects GNodes based on their properties, and zero or more predicates which are used to filter the results.

base URI declaration

A base URI declaration specifies the Static Base URI property. The Static Base URI property is used when resolving relative URI references.

binding collection

In a for clause, when an expression is preceded by the keyword in, the value of that expression is called a binding collection.

binding sequence

In a window clause, when an expression is preceded by the keyword in, the value of that expression is called a binding sequence.

boundary-space declaration

A boundary-space declaration sets the boundary-space policy in the static context, overriding any implementation-defined default. Boundary-space policy controls whether boundary whitespace is preserved by element constructors during processing of the query.

boundary-space policy

Boundary-space policy. This component controls the processing of boundary whitespace by direct element constructors, as described in 4.12.1.4 Boundary Whitespace.

boundary whitespace

Boundary whitespace is a sequence of consecutive whitespace characters within the content of a direct element constructor, that is delimited at each end either by the start or end of the content, or by a DirectConstructor, or by an EnclosedExpr. For this purpose, characters generated by character references such as &#x20; or by CDataSections are not considered to be whitespace characters.

character reference

A character reference is an XML-style reference to a [Unicode] character, identified by its decimal or hexadecimal codepoint.

choice item type

A choice item type defines an item type that is the union of a number of alternatives. For example the type (xs:hexBinary | xs:base64Binary) defines the union of these two primitive atomic types, while the type (map(*) | array(*)) matches any item that is either a map or an array.

coercion rules

The coercion rules are rules used to convert a supplied value to a required type, for example when converting an argument of a function call to the declared type of the function parameter.

collation

A collation is a specification of the manner in which strings and URIs are compared and, by extension, ordered. For a more complete definition of collation, see [Functions and Operators 4.0] section 5.3 Comparison of strings.

comma operator

A comma operator is a comma used specifically as the operator in a sequence expression.

complex terminal

A complex terminal is a variable terminal whose production rule references, directly or indirectly, an ordinary production rule.

computed element constructor

A computed element constructor creates an element node, allowing both the name and the content of the node to be computed.

constructed element namespace rule

When an unprefixed lexical QName is expanded using the constructed element namespace rule, then it uses the namespace URI that is bound to the empty (zero-length) prefix in the statically known namespaces of the static context. If there is no such namespace binding then it uses the no-namespace rule.

construction declaration

A construction declaration sets the construction mode in the static context, overriding any implementation-defined default.

construction mode

Construction mode. The construction mode governs the behavior of element and document node constructors. If construction mode is preserve, the type of a constructed element node is xs:anyType, and all attribute and element nodes copied during node construction retain their original types. If construction mode is strip, the type of a constructed element node is xs:untyped; all element nodes copied during node construction receive the type xs:untyped, and all attribute nodes copied during node construction receive the type xs:untypedAtomic.

constructor function

The constructor function for a given simple type is used to convert instances of other simple types into the given type. The semantics of the constructor function call T($arg) are defined to be equivalent to the expression $arg cast as T?.

content expression

In an enclosed expression, the optional expression enclosed in curly brackets is called the content expression.

context dependent

A function definition is said to be context dependent if its result depends on the static or dynamic context of its caller. 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.

context node

When the context value is a single item, it can also be referred to as the context item; when it is a single node, it can also be referred to as the context node.

context position

The context position is the position of the context value within the series of values currently being processed.

context size

The context size is the number of values in the series of values currently being processed.

context value

The context value is the value currently being processed.

copy-namespaces declaration

A copy-namespaces declaration sets the value of copy-namespaces mode in the static context, overriding any implementation-defined default. Copy-namespaces mode controls the namespace bindings that are assigned when an existing element node is copied by an element constructor or document constructor.

copy-namespaces mode

Copy-namespaces mode. This component controls the in-scope namespaces property that is assigned when an existing element node is copied by an element constructor, as described in 4.12.1 Direct Element Constructors. Its value consists of two parts: preserve or no-preserve, and inherit or no-inherit.

current dateTime

Current dateTime. This information represents an implementation-dependent point in time during the processing of a query , and includes an explicit timezone. It can be retrieved by the fn:current-dateTime function. If called multiple times during the execution of a query , this function always returns the same result.

data model

XQuery 4.0 operates on the abstract, logical structure of an XML document or JSON object rather than its surface syntax. This logical structure, known as the data model, is defined in [XDM 4.0].

decimal-format declaration

A decimal format declaration adds a decimal format to the statically known decimal formats, which define the properties used to format numbers using the fn:format-number() function

decimal-separator

decimal-separator(M, R) is used to separate the integer part of the number from the fractional part. The default value for both the marker and the rendition is U+002E (FULL STOP, PERIOD, .) .

default annotation namespace rule

When an unprefixed lexical QName is expanded using the annotation namespace rule, then it uses the namespace URI http://www.w3.org/2012/xquery.

default calendar

Default calendar. This is the calendar used when formatting dates in human-readable output (for example, by the functions fn:format-date and fn:format-dateTime) if no other calendar is requested. The value is a string.

default collation

Default collation. This identifies one of the collations in statically known collations as the collation to be used by functions and operators for comparing and ordering values of type xs:string and xs:anyURI (and types derived from them) when no explicit collation is specified.

default collation declaration

A default collation declaration sets the value of the default collation in the static context, overriding any implementation-defined default.

default collection

Default collection. This is the sequence of items that would result from calling the fn:collection function with no arguments.

default element namespace rule

When an unprefixed lexical QName is expanded using the default element namespace rule, then it uses the default namespace for elements and types. If this is absent, or if it takes the special value ##any, then the no-namespace rule is used.

default function namespace

Default function namespace. This determines how unprefixed lexical QNames appearing in a static function call or a named function reference are interpreted.

default function namespace rule

When an unprefixed lexical QName is expanded using the default function namespace rule, the processor searches for a matching function definition as follows: first, if the static context includes a no-namespace function definition with the required local name and arity, then that function definition is used; otherwise, the name is expanded using the default function namespace from the static context.

default in-scope namespace

The default in-scope namespace of an element node

default language

Default language. This is the natural language used when creating human-readable output (for example, by the functions fn:format-date and fn:format-integer) if no other language is requested. The value is a language code as defined by the type xs:language.

default namespace for elements and types

Default namespace for elements and types. This is either a namespace URI, or the special value "##any", or absentDM. This indicates how unprefixed QNames are interpreted when they appear in a position where an element name or type name is expected.

default order for empty sequences

Default order for empty sequences. This component controls the processing of empty sequences and NaN values as ordering keys in an order by clause in a FLWOR expression, as described in 4.13.9 Order By Clause.

default place

Default place. This is a geographical location used to identify the place where events happened (or will happen) when processing dates and times using functions such as fn:format-date, fn:format-dateTime, and fn:civil-timezone, if no other place is specified. It is used when translating timezone offsets to civil timezone names, and when using calendars where the translation from ISO dates/times to a local representation is dependent on geographical location. Possible representations of this information are an ISO country code or an Olson timezone name, but implementations are free to use other representations from which the above information can be derived. The only requirement is that it should uniquely identify a civil timezone, which means that country codes for countries with multiple timezones, such as the United States, are inadequate.

default type namespace rule

When an unprefixed lexical QName is expanded using the default type namespace rule, it uses the default namespace for elements and types. If this is absent, the no-namespace rule is used. If the default namespace for elements and types has the special value ##any, then the lexical QName refers to a name in the namespace http://www.w3.org/2001/XMLSchema.

default URI collection

Default URI collection. This is the sequence of URIs that would result from calling the fn:uri-collection function with no arguments.

delimiting terminal symbol

The delimiting terminal symbols are: !!=##)$%((#)**:+,--->->...////>::*:::=;<<!--<![CDATA[</<<<=<?==!>=>=?>>>=>>??>?[@[]]]>]```````[`{{{{|||}}`}}×÷AposStringLiteralBracedURILiteralQuotStringLiteralSStringLiteralURIQualifiedName

depends on

A variable value (or the context value) depends on another variable value (or the context value) if, during the evaluation of the initializing expression of the former, the latter is accessed through the module context.

derives from

A schema typeS1 is said to derive fromschema typeS2 if any of the following conditions is true:

digit

digit(M) is a character used in the picture string to represent an optional digit; the default value is U+0023 (NUMBER SIGN, #) .

direct element constructor

A direct element constructor is a form of element constructor in which the name of the constructed element is a constant.

document order

Informally, document order is the order in which nodes appear in the XML serialization of a document.

dynamically known function definitions

Dynamically known function definitions. This is a set of function definitions. It includes the statically known function definitions as a subset, but may include other function definitions that are not known statically.

dynamic context

The dynamic context of an expression is defined as information that is needed for the dynamic evaluation of an expression, beyond any information that is needed from the static context.

dynamic error

A dynamic error is an error that must be detected during the dynamic evaluation phase and may be detected during the static analysis phase.

dynamic evaluation phase

The dynamic evaluation phase is the phase during which the value of an expression is computed.

dynamic function call

A dynamic function call is an instance of the construct DynamicFunctionCall: that is, it is an expression in the form E1(E2, E3, ...) in which E1 identifies a function item to be called, and the parenthesized argument list (E2, E3, ...)) identifies the arguments supplied to the function.

dynamic type

Every value matches one or more sequence types. A value is said to have a dynamic typeT if it matches (or is an instance of) the sequence type T.

effective boolean value

The effective boolean value of a value is defined as the result of applying the fn:boolean function to the value.

effective case

The effective case of a switch expression is the first case clause that matches, using the rules given above, or the default clause if no such case clause exists.

effective case

The effective case in a typeswitch expression is the first case clause in which the value of the operand expression matches a SequenceType in the SequenceTypeUnion of the case clause, using the rules of SequenceType matching.

element name matching rule

When an unprefixed lexical QName is expanded using the element name matching rule rule, then it uses the default namespace for elements and types. If this is absent, then it uses the no-namespace rule. But if it takes the special value ##any, then the name is taken as matching any expanded QName with the corresponding local part, regardless of namespace: that is, the unprefixed name local is interpreted as *:local.

empty order declaration

An empty order declaration sets the default order for empty sequences in the static context, overriding any implementation-defined default. This declaration controls the processing of empty sequences and NaN values as ordering keys in an order by clause in a FLWOR expression.

empty sequence

A sequence containing zero items is called an empty sequence.

enclosed expression

An enclosed expression is an instance of the EnclosedExpr production, which allows an optional expression within curly brackets.

encoding declaration

If present, a version declaration may optionally include an encoding declaration. The value of the string literal following the keyword encoding is an encoding name, and must conform to the definition of EncName specified in [XML 1.0] [err:XQST0087]. The purpose of an encoding declaration is to allow the writer of a query to provide a string that indicates how the query is encoded, such as "UTF-8", "UTF-16", or "US-ASCII".

entry

Each key / value pair in a map is called an entry.

enumeration type

An EnumerationType accepts a fixed set of string values.

environment variables

Environment variables. This is a mapping from names to values. Both the names and the values are strings. The names are compared using an implementation-defined collation, and are unique under this collation. The set of environment variables is implementation-defined and may be empty.

equivalent grouping keys

Two tuples T1 and T2 have equivalent grouping keys if and only if, for each grouping variable GV, the atomized value of GV in T1 is deep-equal to the atomized value of GV in T2, as defined by applying the function fn:deep-equal using the appropriate collation.

error value

In addition to its identifying QName, a dynamic error may also carry a descriptive string and one or more additional values called error values.

Executable Base URI

Executable Base URI. This is an absolute URI used to resolve relative URIs during the evaluation of expressions; it is used, for example, to resolve a relative URI supplied to the fn:doc or fn:unparsed-text functions.

expanded QName

An expanded QName is a triple: its components are a prefix, a local name, and a namespace URI. In the case of a name in no namespace, the namespace URI and prefix are both absent. In the case of a name in the default namespace, the prefix is absent.

exponent-separator

exponent-separator(M, R) is used to separate the mantissa from the exponent in scientific notation. The default value for both the marker and the rendition is U+0065 (LATIN SMALL LETTER E, e) .

expression context

The expression context for a given expression consists of all the information that can affect the result of the expression.

extension expression

An extension expression is an expression whose semantics are implementation-defined.

external function

External functions can be characterized as functions that are neither part of the processor implementation, nor written in a language whose semantics are under the control of this family of specifications. The semantics of external functions, including any context dependencies, are entirely implementation-defined. In XSLT, external functions are called 24.1 Extension Functions XT30.

filter expression

A filter expression is an instance of the construct FilterExpr: that is, it is an expression in the form E1[E2]. Its effect is to return those items from the value of E1 that satisfy the predicate in E2.

filter expression for maps and arrays

A filter expression for maps and arrays is an instance of the construct FilterExprAM: that is, it is an expression in the form E1?[E2]. Its effect is to evaluate E1 to return an array or map, and to select members of the array, or entries from the map, that satisfy the predicate in E2.

fixed focus

A fixed focus is a focus for an expression that is evaluated once, rather than being applied to a series of values; in a fixed focus, the context value is set to one specific value, the context position is 1, and the context size is 1.

focus

The first three components of the dynamic context (context value, context position, and context size) are called the focus of the expression.

focus function

A focus function is an inline function expression in which the function signature is implicit: the function takes a single argument of type item()* (that is, any value), and binds this to the context value when evaluating the function body, which returns a result of type item()*.

function assertion

A function assertion is a predicate that restricts the set of functions matched by a FunctionType. It uses the same syntax as 5.15 Annotations.

function coercion

Function coercion wraps a function item in a new function whose signature is the same as the expected type. This effectively delays the checking of the argument and return types until the function is called.

function definition

A function definition contains information used to evaluate a static function call, including the name, parameters, and return type of the function.

function item

A function item is an item that can be called using a dynamic function call.

generalized atomic type

A generalized atomic type is an item type whose instances are all atomic items. Generalized atomic types include (a) atomic types, either built-in (for example xs:integer) or imported from a schema, (b) pure union types, either built-in (xs:numeric and xs:error) or imported from a schema, (c) choice item types if their alternatives are all generalized atomic types, and (d) enumeration types.

GNode

The term generic node or GNode is a collective term for XNodes (more commonly called simply nodes) representing the parts of an XML document, and JNodes, often used to represent the parts of a JSON document.

grouping key

The atomized value of a grouping variable is called a grouping key.

grouping-separator

grouping-separator(M, R) is used to separate groups of digits (for example as a thousands separator). The default value for both the marker and the rendition is U+002C (COMMA, ,) .

grouping variable

Each grouping specification specifies one grouping variable, which refers to variable bindings in the pre-grouping tuples. The values of the grouping variables are used to assign pre-grouping tuples to groups.

GTree

The term GTree means JTree or XTree.

guarded

An expression E is said to be guarded by some governing condition C if evaluation of E is not allowed to fail with a dynamic error except when C applies.

ignorable whitespace

Ignorable whitespace consists of any whitespace characters that may occur between terminals, unless these characters occur in the context of a production marked with a ws:explicit annotation, in which case they can occur only where explicitly specified (see A.3.4.2 Explicit Whitespace Handling).

implausible

Certain expressions, while not erroneous, are classified as being implausible, because they achieve no useful effect.

implementation defined

Implementation-defined indicates an aspect that may differ between implementations, but must be specified by the implementer for each particular implementation.

implementation dependent

Implementation-dependent indicates an aspect that may differ between implementations, is not specified by this or any W3C specification, and is not required to be specified by the implementer for any particular implementation.

implicit timezone

Implicit timezone. This is the timezone to be used when a date, time, or dateTime value that does not have a timezone is used in a comparison or arithmetic operation. The implicit timezone is an implementation-defined value of type xs:dayTimeDuration. See 3.2.7.3 Timezones XS1-2 or 3.3.7 dateTime XS11-2 for the range of valid values of a timezone.

infinity

infinity(R) is the string used to represent the double value infinity (INF); the default value is the string "Infinity"

initial context value

In the dynamic context of every module in a query, the context value component must have the same setting. If this shared setting is not absentDM, it is referred to as the initial context value.

initializing expression

If a variable declaration includes an expression (VarValue or VarDefaultValue), the expression is called an initializing expression. The static context for an initializing expression includes all functions, variables, and namespaces that are declared or imported anywhere in the Prolog.

inline function expression

An inline function expression is an instance of the construct InlineFunctionExpr. When evaluated, an inline function expression creates an anonymous function whose properties are defined directly in the inline function expression.

in-scope attribute declarations

In-scope attribute declarations. Each attribute declaration is identified either by an expanded QName (for a top-level attribute declaration) or by an implementation-dependent attribute identifier (for a local attribute declaration). If the Schema Aware Feature is supported, in-scope attribute declarations include all attribute declarations found in imported schemas.

in-scope element declarations

In-scope element declarations. Each element declaration is identified either by an expanded QName (for a top-level element declaration) or by an implementation-dependent element identifier (for a local element declaration). If the Schema Aware Feature is supported, in-scope element declarations include all element declarations found in imported schemas.

in-scope named item types

In-scope named item types. This is a mapping from expanded QNames to named item types.

in-scope namespaces

The in-scope namespaces property of an element node is a set of namespace bindings, each of which associates a namespace prefix with a URI.

in-scope schema definitions

In-scope schema definitions is a generic term for all the element declarations, attribute declarations, and schema type definitions that are in scope during static analysis of an expression.

in-scope schema type

In-scope schema types. Each schema type definition is identified either by an expanded QName (for a named type) or by an implementation-dependent type identifier (for an anonymous type). The in-scope schema types include the predefined schema types described in 3.5 Schema Types. If the Schema Aware Feature is supported, in-scope schema types also include all type definitions found in imported schemas.

in-scope variables

In-scope variables. This is a mapping from expanded QNames to sequence types. It defines the set of variables that are available for reference within an expression. The expanded QName is the name of the variable, and the type is the static type of the variable.

item

An item is either an atomic item, a node, or a function item.

item type

An item type is a type that can be expressed using the ItemType syntax, which forms part of the SequenceType syntax. Item types match individual items.

item type designator

An item type designator is a syntactic construct conforming to the grammar rule ItemType. An item type designator is said to designate an item type.

JNode

A JNode is a kind of item used to represent a value within the context of a tree of maps and arrays. A root JNode represents a map or array; a non-root JNode represents a member of an array or an entry in a map.

JTree

A tree that is rooted at a parentless JNode is referred to as a JTree.

lexical QName

A lexical QName is a name that conforms to the syntax of the QName production

library module

A module that does not contain a Query Body is called a library module. A library module consists of a module declaration followed by a Prolog.

literal

A literal is a direct syntactic representation of an atomic item.

literal terminal

A literal terminal is a token appearing as a string in quotation marks on the right-hand side of an ordinary production rule.

logical expression

A logical expression is either an and expression or an or expression. If a logical expression does not raise an error, its value is always one of the boolean values true or false.

lookup expression

A lookup expression is an instance of the production LookupExpr: that is, an expression in the form E1?KS, where E1 is an expression returning a sequence of maps or arrays, and KS is a key specifier, which indicates which entries in a map, or members in an array, should be selected.

main module

A main module consists of a Prolog followed by a Query Body.

map

A map is a function that associates a set of keys with values, resulting in a collection of key / value pairs.

mapping arrow operator

The mapping arrow operator=!> applies a function to each item in a sequence.

may

MAY means that an item is truly optional.

member

The values of an array are called its members.

minus-sign

minus-sign(R) is the string used to mark negative numbers; the default value is U+002D (HYPHEN-MINUS, -) .

module

A module is a fragment of XQuery code that conforms to the Module grammar and can independently undergo the static analysis phase described in 2.4.3 Expression Processing. Each module is either a main module or a library module.

module declaration

A module declaration serves to identify a module as a library module. A module declaration begins with the keyword module and contains a namespace prefix and a URILiteral.

module import

A module import imports the public variable declarations, public function declarations, and public item type declarations from one or more library modules into the statically known function definitions, in-scope variables, or in-scope named item types of the importing module.

must

MUST means that the item is an absolute requirement of the specification.

must not

MUST NOT means that the item is an absolute prohibition of the specification.

named function reference

A named function reference is an instance of the production NamedFunctionRef: it is an expression (written name#arity) which evaluates to a function item, the details of the function item being based on the properties of a function definition in the static context.

named item type

A named item type is an ItemType identified by an expanded QName.

name expression

When an expression is used to specify the name of a constructed node, that expression is called the name expression of the constructor.

namespace binding

A namespace binding is a pair comprising a namespace prefix (which is either an xs:NCName or empty), and a namespace URI.

namespace declaration

A namespace declaration declares a namespace prefix and associates it with a namespace URI, adding the (prefix, URI) pair to the set of statically known namespaces.

namespace declaration attribute

A namespace declaration attribute is used inside a direct element constructor. Its purpose is to bind a namespace prefix (including the zero-length prefix) for the constructed element node, including its attributes.

namespace-sensitive

The namespace-sensitive types are xs:QName, xs:NOTATION, types derived by restriction from xs:QName or xs:NOTATION, list types that have a namespace-sensitive item type, and union types with a namespace-sensitive type in their transitive membership.

name test

A node test that consists only of an EQName or a Wildcard is called a name test.

NaN

NaN(R) is the string used to represent the double value NaN (not a number); the default value is the string "NaN"

node

Except where the context indicates otherwise, the term node is used as a synonym for XNode.

node test

A node test is a condition on the properties of a GNode. A node test determines which GNodes returned by an axis are selected by a step.

no-namespace rule

When an unprefixed lexical QName is expanded using the no-namespace rule, it is interpreted as having an absent namespace URI.

non-delimiting terminal symbol

The non-delimiting terminal symbols are: allowingancestorancestor-or-selfandarrayasascendingatattributebase-uriboundary-spacebycasecastcastablecatchchildcollationcommentconstructioncontextcopy-namespacescountdecimal-formatdecimal-separatordeclaredefaultdescendantdescendant-or-selfdescendingdigitdivdocumentdocument-nodeelementelseemptyempty-sequenceencodingendenumeqeveryexceptexponent-separatorexternalfalsefinallyfixedfnfollowingfollowing-or-selffollowing-siblingfollowing-sibling-or-selffollowsfollows-or-isforfunctiongegetgnodegreatestgroupgrouping-separatorgtidivifimportininfinityinheritinstanceintersectisis-notitemjnodekeylaxleleastletltmapmemberminus-signmodmodulenamespacenamespace-nodeNaNnenextno-inheritno-preservenodeofonlyoptionororderorderedorderingotherwiseparentpattern-separatorper-millepercentprecedesprecedes-or-isprecedingpreceding-or-selfpreceding-siblingpreceding-sibling-or-selfpreservepreviousprocessing-instructionrecordreturnsatisfiesschemaschema-attributeschema-elementselfslidingsomestablestartstrictstripswitchtextthentotreattruetrytumblingtypetypeswitchunionunorderedvalidatevaluevariableversionwhenwherewhilewindowxqueryzero-digitBinaryIntegerLiteralDecimalLiteralDoubleLiteralHexIntegerLiteralIntegerLiteralNCNameQName

non-trivial

A construct is said to be a non-trivial instance of a grammatical production if it is not also an instance of one of its sub-productions.

numeric

The type xs:numeric is defined as a union type with member types xs:double, xs:float, and xs:decimal. An item that is an instance of any of these types is referred to as a numeric value, and a type that is a subtype of xs:numeric is referred to as a numeric type.

numeric predicate

A predicate whose predicate expression returns a value of type xs:numeric+ is called a numeric predicate.

option declaration

An option declaration declares an option that affects the behavior of a particular implementation. Each option consists of an identifying EQName and a StringLiteral.

ordinary production rule

An ordinary production rule is a production rule in A.1 EBNF that is not annotated ws:explicit.

or expression

An or expression is a non-trivial instance of the production OrExpr.

output declaration

An output declaration is an option declaration in the namespace http://www.w3.org/2010/xslt-xquery-serialization; it is used to declare serialization parameters.

partial function application

A static or dynamic function call is a partial function application if one or more arguments is an ArgumentPlaceholder.

partially applied function

A partially applied function is a function created by partial function application.

path expression

A path expression is either an absolute path expression or a relative path expression

pattern-separator

pattern-separator(M) is a character used to separate positive and negative sub-pictures in a picture string; the default value is U+003B (SEMICOLON, ;) .

percent

percent(M, R) is used to indicate that the number is written as a per-hundred fraction; the default value for both the marker and the rendition is U+0025 (PERCENT SIGN, %) .

per-mille

per-mille(M, R) is used to indicate that the number is written as a per-thousand fraction; the default value for both the marker and the rendition is U+2030 (PER MILLE SIGN, ) .

pipeline operator

The pipeline operator-> evaluates an expression and binds the result to the context value before evaluating another expression.

positional variable

A positional variable is a variable that is preceded by the keyword at.

pragma

A pragma is denoted by the delimiters (# and #), and consists of an identifying EQName followed by implementation-defined content.

predefined entity reference

A predefined entity reference is a short sequence of characters, beginning with an ampersand, that represents a single character that might otherwise have syntactic significance.

predicate truth value

The predicate truth value of a value $V is the result of the expression if ($V instance of xs:numeric+) then ($V = position()) else fn:boolean($V).

primary expression

A primary expression is an instance of the production PrimaryExpr. Primary expressions are the basic primitives of the language. They include literals, variable references, context value references, constructors, and function calls. A primary expression may also be created by enclosing any expression in parentheses, which is sometimes helpful in controlling the precedence of operators.

principal node kind

Every axis has a principal node kind. If an axis can contain elements, then the principal node kind is element; otherwise, it is the kind of nodes that the axis can contain.

private function

A private function is a function with a %private annotation. A private function is hidden from module import, which can not import it into the statically known function definitions of another module.

private item type

A private item type is a named item type with a %private annotation. A private item type is hidden from module import, which can not import it into the in-scope named item types of another module.

private variable

A private variable is a variable with a %private annotation. A private variable is hidden from module import, which can not import it into the in-scope variables of another module.

Prolog

A Prolog is a series of declarations and imports that define the processing environment for the module that contains the Prolog.

public function

A public function is a function without a %private annotation. A public function is accessible to module import, which can import it into the statically known function definitions of another module.

public item type

A public item type is an item type declaration without a %private annotation. A public item type is accessible to module import, which can import it into the in-scope named item types of another module.

public variable

A public variable is a variable without a %private annotation. A public variable is accessible to module import, which can import it into the in-scope variables of another module. Using %public and %private annotations in a main module is not an error, but it does not affect module imports, since a main module cannot be imported. It is a static error [err:XQST0116] if a variable declaration contains both a %private and a %public annotation, more than one %private annotation, or more than one %public annotation.

pure union type

A pure union type is a simple type that satisfies the following constraints: (a) {variety}XS11-1 is union, (b) the {facets}XS11-1 property is empty, (c) no type in the transitive membership of the union type has {variety}XS11-1list, and (d) no type in the transitive membership of the union type is a type with {variety}XS11-1union having a non-empty {facets}XS11-1 property

query

A query consists of one or more modules.

query body

The Query Body, if present, consists of an expression that defines the result of the query.

range expression

A range expression is a non-trivial instance of the production RangeExpr. A range expression is used to construct a sequence of integers.

relative path expression

A relative path expression is a non-trivial instance of the production RelativePathExpr: it consists of two or more operand expressions separated by / or // operators.

reserved namespaces

A reserved namespace is a namespace that must not be used in the name of a function declaration.

resolve

To resolve a relative URI$rel against a base URI $base is to expand it to an absolute URI, as if by calling the function fn:resolve-uri($rel, $base).

reverse document order

The node ordering that is the reverse of document order is called reverse document order.

same key

Two atomic items K1 and K2 have the same key value if fn:atomic-equal(K1, K2) returns true, as specified in [Functions and Operators 4.0] section 2.2.1 fn:atomic-equal

schema aware feature

The Schema Aware Feature permits the query Prolog to contain a schema import, and permits a query to contain a validate expression (see 4.25 Validate Expressions).

schema import

A schema import imports the element declarations, attribute declarations, and type definitions from a schema into the in-scope schema definitions. For each named user-defined simple type in the schema, schema import also adds a corresponding constructor function.

schema type

A schema type is a complex type or simple type as defined in the [XML Schema 1.0] or [XML Schema 1.1] specifications, including built-in types as well as user-defined types.

sequence

A sequence is an ordered collection of zero or more items.

sequence arrow operator

The sequence arrow operator=> applies a function to a supplied sequence.

sequence concatenation

The sequence concatenation of a number of sequences S1, S2, ... Sn is defined to be the sequence formed from the items of S1, followed by the items from S2, and so on, retaining order.

sequence expression

A sequence expression is a non-trivial instance of the production rule Expr, that is, an expression containing two or more instances of the production ExprSingle separated by the comma operator.

sequence type

A sequence type is a type that can be expressed using the SequenceType syntax. Sequence types are used whenever it is necessary to refer to a type in an XQuery 4.0 expression. Since all values are sequences, every value matches one or more sequence types.

sequence type designator

A sequence type designator is a syntactic construct conforming to the grammar rule SequenceType. A sequence type designator is said to designate a sequence type.

SequenceType matching

SequenceType matching compares a value with an expected sequence type.

serialization

Serialization is the process of converting an XDM instance to a sequence of octets (step DM4 in Figure 1.), as described in [Serialization 4.0].

serialization feature

The Serialization Feature provides means for serializing the result of a query as specified in 2.4.5 Serialization.

setter

Setters are declarations that set the value of some property that affects query processing, such as construction mode or default collation.

should

SHOULD means that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course.

singleton

A sequence containing exactly one item is called a singleton.

singleton enumeration type

An enumeration type with a single enumerated value E (such as enum("red")) matches an item S if and only if (a) S is an instance of xs:string, and (b) S is equal to E when compared using Unicode codepoint collation. This is referred to as a singleton enumeration type.

singleton focus

A singleton focus is a fixed focus in which the context value is a singleton item.

stable

Document order is stable, which means that the relative order of two nodes will not change during the processing of a given query , even if this order is implementation-dependent.

statically known collations

Statically known collations. This is an implementation-defined mapping from URI to collation. It defines the names of the collations that are available for use in processing queries and expressions.

statically known decimal formats

Statically known decimal formats. This is a mapping from QNames to decimal formats, with one default format that has no visible name, referred to as the unnamed decimal format. Each format is available for use when formatting numbers using the fn:format-number function.

statically known function definitions

Statically known function definitions. This is a set of function definitions.

statically known namespaces

Statically known namespaces. This is a mapping from prefix to namespace URI that defines all the namespaces that are known during static processing of a given expression.

static analysis phase

The static analysis phase depends on the expression itself and on the static context. The static analysis phase does not depend on input data (other than schemas).

Static Base URI

Static Base URI. This is an absolute URI, used to resolve relative URIs during static analysis.

static context

The static context of an expression is the information that is available during static analysis of the expression, prior to its evaluation.

static error

An error that can be detected during the static analysis phase, and is not a type error, is a static error.

static function call

A static function call is an instance of the production FunctionCall: it consists of an EQName followed by a parenthesized list of zero or more arguments.

static type

The static type of an expression is the best inference that the processor is able to make statically about the type of the result of the expression.

step

The operands of a path expression are conventionally referred to as steps.

string constructor

A string constructor is an instance of the production StringConstructor: it is an expression that creates a string from literal text and interpolated subexpressions.

string value

The string value of a node is a string and can be extracted by applying the string function to the node.

substantively disjoint

Two sequence types are deemed to be substantively disjoint if (a) neither is a subtype of the other (see 3.3.1 Subtypes of Sequence Types) and (b) the only values that are instances of both types are one or more of the following:

substitution group

Substitution groups are defined in 2.2.2.2 Element Substitution Group XS1-1 and 2.2.2.2 Element Substitution Group XS11-1. Informally, the substitution group headed by a given element (called the head element) consists of the set of elements that can be substituted for the head element without affecting the outcome of schema validation.

subtype

Given two sequence types or item types, the rules in this section determine if one is a subtype of the other. If a type A is a subtype of type B, it follows that every value matched by A is also matched by B.

subtype substitution

The use of a value that has a dynamic type that is a subtype of the expected type is known as subtype substitution.

symbol

Each rule in the grammar defines one symbol, using the following format:

symbol ::= expression
symbol separators

Whitespace and Comments function as symbol separators. For the most part, they are not mentioned in the grammar, and may occur between any two terminal symbols mentioned in the grammar, except where that is forbidden by the /* ws: explicit */ annotation in the EBNF, or by the /* xgc: xml-version */ annotation.

system function

System functions include the functions defined in [Functions and Operators 4.0], functions defined by the specifications of a host language, constructor functions for atomic types, and any additional functions provided by the implementation. System functions are sometimes called built-in functions.

target namespace

The target namespace of a module is the namespace of the objects (such as elements or functions) that it defines.

terminal

A terminal is a symbol or string or pattern that can appear in the right-hand side of a rule, but never appears on the left-hand side in the main grammar, although it may appear on the left-hand side of a rule in the grammar for terminals.

trusted

The static context includes a boolean property called trusted that determines whether external resources are available.

tuple

A tuple is a set of zero or more named variables, each of which is bound to a value that is an XDM instance.

tuple stream

A tuple stream is an ordered sequence of zero or more tuples.

type annotation

Each element node and attribute node in an XDM instance has a type annotation (described in [XDM 4.0] section 4.1 Schema Information). The type annotation of a node is a reference to a schema type.

typed data feature

The Typed Data Feature permits an XDM instance to contain element node types other than xs:untyped and attributes node types other than xs:untypedAtomic.

type declaration

A variable binding may be accompanied by a type declaration, which consists of the keyword as followed by the static type of the variable, declared using the syntax in 3.1 Sequence Types.

typed value

The typed value of a node is a sequence of atomic items and can be extracted by applying the data function to the node.

type error

A type error may be raised during the static analysis phase or the dynamic evaluation phase. During the static analysis phase, a type error occurs when the static type of an expression does not match the expected type of the context in which the expression occurs. During the dynamic evaluation phase, a type error occurs when the dynamic type of a value does not match the expected type of the context in which the value occurs.

untrusted

Code executing with trusted set to false is said to be untrusted.

URI

Within this specification, the term URI refers to a Universal Resource Identifier as defined in [RFC3986] and extended in [RFC3987] with the new name IRI.

user-defined function

User defined functions are functions that contain a function body, which provides the implementation of the function as a content expression.

value

In the data model, a value is always a sequence.

variable declaration

A variable declaration in the XQuery prolog defines the name and static type of a variable, and optionally a value for the variable. It adds to the in-scope variables in the static context, and may also add to the variable values in the dynamic context.

variable reference

A variable reference is an EQName preceded by a $-sign.

variable terminal

A variable terminal is an instance of a production rule that is not itself an ordinary production rule but that is named (directly) on the right-hand side of an ordinary production rule.

variable values

Variable values. This is a mapping from expanded QNames to values. It contains the same expanded QNames as the in-scope variables in the static context for the expression. The expanded QName is the name of the variable and the value is the dynamic value of the variable, which includes its dynamic type.

version declaration

A version declaration can identify the applicable XQuery syntax and semantics for a module, as well as its encoding.

warning

In addition to static errors, dynamic errors, and type errors, an XQuery 4.0 implementation may raise warnings, either during the static analysis phase or the dynamic evaluation phase. The circumstances in which warnings are raised, and the ways in which warnings are handled, are implementation-defined.

whitespace

A whitespace character is any of the characters defined by [http://www.w3.org/TR/REC-xml/#NT-S].

wildcard-matches

In these rules, if MU and NU are NameTestUnions, then MUwildcard-matchesNU is true if every name that matches MU also matches NU.

window

A window is a sequence of consecutive items drawn from the binding sequence.

XDM instance

The term XDM instance is used, synonymously with the term value, to denote an unconstrained sequence of items.

XNode

An XNode is an instance of one of the node kinds defined in [XDM 4.0] section 7.1 XML Nodes.

XPath 1.0 compatibility mode

XPath 1.0 compatibility mode.This component must be set by all host languages that include XPath 3.1 as a subset, indicating whether rules for compatibility with XPath 1.0 are in effect. XQuery sets the value of this component to false.

XQuery 1.0 Processor

An XQuery 1.0 Processor processes a query according to the XQuery 1.0 specification.

XQuery 3.0 Processor

An XQuery 3.0 Processor processes a query according to the XQuery 3.0 specification.

XQuery 3.1 Processor

An XQuery 3.1 Processor processes a query according to the XQuery 3.1 specification.

XQuery 4.0 Processor

An XQuery 4.0 Processor processes a query according to the XQuery 4.0 specification.

XQuery version number

An XQuery version number consists of two integers, referred to as the major version number and the minor version number.

xs:anyAtomicType

xs:anyAtomicType is an atomic type that includes all atomic items (and no values that are not atomic). Its base type is xs:anySimpleType from which all simple types, including atomic, list, and union types, are derived. All primitive atomic types, such as xs:decimal and xs:string, have xs:anyAtomicType as their base type.

xs:dayTimeDuration

xs:dayTimeDuration is derived by restriction from xs:duration. The lexical representation of xs:dayTimeDuration is restricted to contain only day, hour, minute, and second components.

xs:error

xs:error is a simple type with no value space. It is defined in 3.16.7.3 xs:error XS11-1 and can be used in the 3.1 Sequence Types to raise errors.

xs:untyped

xs:untyped is used as the type annotation of an element node that has not been validated, or has been validated in skip mode.

xs:untypedAtomic

xs:untypedAtomic is an atomic type that is used to denote untyped atomic data, such as text that has not been assigned a more specific type.

xs:yearMonthDuration

xs:yearMonthDuration is derived by restriction from xs:duration. The lexical representation of xs:yearMonthDuration is restricted to contain only year and month components.

XTree

A tree that is rooted at a parentless XNode is referred to as an XTree.

zero-digit

zero-digit(M) is the character used in the picture string to represent the digit zero; the default value is U+0030 (DIGIT ZERO, 0) . This character must be a digit (category Nd in the Unicode property database), and it must have the numeric value zero. This property implicitly defines the ten Unicode characters that are used to represent the values 0 to 9 in the function output: Unicode is organized so that each set of decimal digits forms a contiguous block of characters in numerical sequence. Within the picture string any of these ten character can be used (interchangeably) as a place-holder for a mandatory digit. Within the final result string, these ten characters are used to represent the digits zero to nine.