XML Path Language (XPath) 4.0 WG Review Draft

A XPath 4.0 Grammar

F 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 Section 2.1.4 fn:data^FO.

available binary resources

Available binary resources. This is a mapping of strings to binary resources. Each string represents the absolute URI of a resource. The resource is returned by the fn:unparsed-binary function when applied to that URI.

available documents

Available documents. This is a mapping of strings to document nodes. Each string represents the absolute URI of a resource. The document node is the root of a tree that represents that resource using the data model. The document node is returned by the fn:doc function when applied to that URI.

available item collections

Available collections. This is a mapping of strings to sequences of items. Each string represents the absolute URI of a resource. The sequence of items represents the result of the fn:collection function when that URI is supplied as the argument.

available text resources

Available text resources. This is a mapping of strings to text resources. Each string represents the absolute URI of a resource. The resource is returned by the fn:unparsed-text function when applied to that URI.

available uri collections

Available URI collections. This is a mapping of strings to sequences of URIs. The string represents the absolute URI of a resource which can be interpreted as an aggregation of a number of individual resources each of which has its own URI. The sequence of URIs represents the result of the fn:uri-collection function when that URI is supplied as the argument.

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.

binding collection

The result of evaluating the binding expression in a for expression is called the binding collection

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 Section 5.3 Comparison of strings^FO.

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.

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.

current dateTime

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

data model

XPath 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 [XQuery and XPath Data Model (XDM) 4.0].

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 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 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 is either a namespace URI, or absent^DM. The namespace URI, if present, is used for any unprefixed QName appearing in a position where a function name is expected.

default function namespace rule

When an unprefixed lexical QName is expanded using the default function namespace rule, it uses 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 absent^DM. This indicates how unprefixed QNames are interpreted when they appear in a position where an element name or type name is expected.

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: !!=#$%method()**:+,-->...///::*:::=<<<<===!>=>>>=>>??[@[]```{{{|||}}}×÷AposStringLiteralBracedURILiteralQuotStringLiteralStringLiteral

derives from

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

• S₁ is the same type as S₂.

• S₂ is the base type of S₁.

• S₂ is a pure union type of which S₁ is a member type.

• There is a schema typeM such that S₁derives fromM and Mderives fromS₂.

digit

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

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

is

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, as defined in Section 8.3.1 fn:boolean^FO.

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 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.

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.

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.

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 Section 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 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-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, ,) .

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.

host language

A host language for XPath is any environment that provides capabilities for XPath expressions to be defined and evaluated, and that supplies a static and dynamic context for their evaluation.

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.3.5.2 Explicit Whitespace HandlingA.3.5.2 Explicit Whitespace Handling).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 HandlingA.3.4.2 Explicit Whitespace Handling).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.3.5.2 Explicit Whitespace HandlingA.3.4.2 Explicit Whitespace HandlingA.3.5.23.4.2 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 Section 3.2.7.3 Timezones ^XS1-2 or Section 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"

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).

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).

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.

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.

kind test

An alternative form of a node test called a type test can select XNodes based on their type, or in the case of JNodes, the type of their contained ·content·

lexical QName

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

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.

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.

method

A method is a function item that has the annotation %method.

minus-sign

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

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.

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-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: ancestorancestor-or-selfandarrayasatattributecastcastablechildcommentdescendantdescendant-or-selfdivdocument-nodeelementelseempty-sequenceenumeqeveryexceptfnfollowingfollowing-or-selffollowing-siblingfollowing-sibling-or-selffollowsforfunctiongegetgnodegtidivifininstanceintersectisis-notitemjnodekeyleletltmapmembermodnamespacenamespace-nodenenodeoforotherwiseparentprecedesprecedingpreceding-or-selfpreceding-siblingpreceding-sibling-or-selfprocessing-instructionrecordreturnsatisfiesschema-attributeschema-elementselfsometextthentotreattypeunionvalueBinaryIntegerLiteralDecimalLiteralDoubleLiteralHexIntegerLiteralIntegerLiteralNCNameQNameURIQualifiedName

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.

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.

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.

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, 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.

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

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.

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 Section 14.2.1 fn:atomic-equal^FO

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, ... S_n 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 XPath 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 [XSLT and XQuery Serialization 4.0].

singleton

A sequence containing exactly one item is called a singleton.

singleton enumeration type

An enumeration type with a single enumerated value (such as enum("red")) is an anonymous atomic type derived from xs:string by restriction using an enumeration facet that permits only the value "red". 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 expression, 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 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 value

The string value of a node is a string and can be extracted by applying the Section 2.1.3 fn:string^FO 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:

• The empty sequence, ().

• The empty map^DM, {}.

• The empty array^DM, [].

substitution group

Substitution groups are defined in Section 2.2.2.2 Element Substitution Group ^XS1-1 and Section 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 [XQuery and XPath 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.

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.

type annotation

Each element node and attribute node in an XDM instance has a type annotation (described in Section 4.1 Schema Information^DM). The type annotation of a node is a reference to a schema type.

typed value

The typed value of a node is a sequence of atomic items and can be extracted by applying the Section 2.1.4 fn:data^FO 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.

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.

value

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

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.

warning

In addition to static errors, dynamic errors, and type errors, an XPath 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.

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 Section 7.1 XML Nodes^DM.

XPath 1.0 compatibility mode

XPath 1.0 compatibility mode.This value is true if rules for backward compatibility with XPath Version 1.0 are in effect; otherwise it is false.

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 Section 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.

I Change Log (Non-Normative)

1. Use the arrows to browse significant changes since the 3.1 version of this specification.

   See 1 Introduction

2. Sections with significant changes are marked Δ in the table of contents.

   See 1 Introduction

3. Setting the default namespace for elements and types to the special value ##any causes an unprefixed element name to act as a wildcard, matching by local name regardless of namespace.

   See 3.2.7.2 Element Types

4. The terms FunctionType, ArrayType, MapType, and RecordType replace FunctionTest, ArrayTest, MapTest, and RecordTest, with no change in meaning.

   See 3.2.8.1 Function Types

5. Record types are added as a new kind of ItemType, constraining the value space of maps.

   See 3.2.8.3 Record Types

6. Function coercion now allows a function with arity N to be supplied where a function of arity greater than N is expected. For example this allows the function true#0 to be supplied where a predicate function is required.

   See 3.4.4 Function Coercion

7. PR 1817 1853 

   An inline function may be annotated as a %method, giving it access to its containing map.

   See 4.5.6 Inline Function Expressions

   See 4.5.6.1 Methods

   See 4.13.3 Lookup Expressions

8. The symbols × and ÷ can be used for multiplication and division.

   See 4.8 Arithmetic Expressions

9. The rules for value comparisons when comparing values of different types (for example, decimal and double) have changed to be transitive. A decimal value is no longer converted to double, instead the double is converted to a decimal without loss of precision. This may affect compatibility in edge cases involving comparison of values that are numerically very close.

   See 4.10.1 Value Comparisons

10. Operators such as < and > can use the full-width forms ＜ and ＞ to avoid the need for XML escaping.

    See 4.10.2 General Comparisons

11. Operators such as < and > can use the full-width forms ＜ and ＞ to avoid the need for XML escaping.

    See 4.10.2 General Comparisons

12. Operator is-not is introduced, as a complement to the operator is.

    See 4.10.3 GNode Comparisons

13. Operators precedes and follows are introduced as synonyms for operators << and >>.

    See 4.10.3 GNode Comparisons

14. The lookup operator ? can now be followed by a string literal, for cases where map keys are strings other than NCNames. It can also be followed by a variable reference.

    See 4.13.3 Lookup Expressions

15. PR 1763 1830 

    The syntax on the right-hand side of an arrow operator has been relaxed; a dynamic function call no longer needs to start with a variable reference or a parenthesized expression, it can also be (for example) an inline function expression or a map or array constructor.

    See 4.20 Arrow Expressions

16. The arrow operator => is now complemented by a “mapping arrow” operator =!> which applies the supplied function to each item in the input sequence independently.

    See 4.20.2 Mapping Arrow Expressions

17. PR 1023 1128 

    It has been clarified that function coercion applies even when the supplied function item matches the required function type. This is to ensure that arguments supplied when calling the function are checked against the signature of the required function type, which might be stricter than the signature of the supplied function item.

    See 3.4.4 Function Coercion

18. A dynamic function call can now be applied to a sequence of functions, and in particular to an empty sequence. This makes it easier to chain a sequence of calls.

    See 4.5.3.1 Evaluating Dynamic Function Calls

19. The syntax document-node(N), where N is a NameTestUnion, is introduced as an abbreviation for document-node(element(N)). For example, document-node(*) matches any well-formed XML document (as distinct from a document fragment).

    See 3.2.7 Node Types

20. QName literals are new in 4.0.

    See 4.2.1.3 QName Literals

21. Path expressions are extended to handle JNodes (found in trees of maps and arrays) as well as XNodes (found in trees representing parsed XML).

    See 4.6 Path Expressions

22. PR 28 

    Multiple for and let clauses can be combined in an expression without an intervening return keyword.

    See 4.12.1 For Expressions

    See 4.12.2 Let Expressions

23. PR 159 

    Keyword arguments are allowed on static function calls, as well as positional arguments.

    See 4.5.1.1 Static Function Call Syntax

24. PR 202 

    The presentation of the rules for the subtype relationship between sequence types and item types has been substantially rewritten to improve clarity; no change to the semantics is intended.

    See 3.3 Subtype Relationships

25. PR 230 

    The rules for “errors and optimization” have been tightened up to disallow many cases of optimizations that alter error behavior. In particular there are restrictions on reordering the operands of and and or, and of predicates in filter expressions, in a way that might allow the processor to raise dynamic errors that the author intended to prevent.

    See 2.4.5 Guarded Expressions

26. PR 254 

    The term "function conversion rules" used in 3.1 has been replaced by the term "coercion rules".

    See 3.4 Coercion Rules

    The coercion rules allow “relabeling” of a supplied atomic item where the required type is a derived atomic type: for example, it is now permitted to supply the value 3 when calling a function that expects an instance of xs:positiveInteger.

    See 3.4 Coercion Rules

27. PR 284 

    Alternative syntax for conditional expressions is available: if (condition) { X }.

    See 4.14 Conditional Expressions

28. PR 286 

    Element and attribute tests can include alternative names: element(chapter|section), attribute(role|class).

    See 3.2.7 Node Types

    The NodeTest in an AxisStep now allows alternatives: ancestor::(section|appendix)

    See 3.2.7 Node Types

    Element and attribute tests of the form element(N) and attribute(N) now allow N to be any NameTest, including a wildcard.

    See 3.2.7.2 Element Types

    See 3.2.7.3 Attribute Types

29. PR 324 

    String templates provide a new way of constructing strings: for example `{$greeting}, {$planet}!` is equivalent to $greeting || ', ' || $planet || '!'

    See 4.9.2 String Templates

30. PR 326 

    Support for higher-order functions is now a mandatory feature (in 3.1 it was optional).

    See 5 Conformance

31. PR 344 

    A for member clause is added to FLWOR expressions to allow iteration over an array.

    See 4.12.1 For Expressions

32. PR 368 

    The concept of the context item has been generalized, so it is now a context value. That is, it is no longer constrained to be a single item.

    See 2.2.2 Dynamic Context

33. PR 433 

    Numeric literals can now be written in hexadecimal or binary notation; and underscores can be included for readability.

    See 4.2.1.1 Numeric Literals

34. PR 519 

    The rules for tokenization have been largely rewritten. In some cases the revised specification may affect edge cases that were handled in different ways by different 3.1 processors, which could lead to incompatible behavior.

    See A.3 Lexical structure

35. PR 521 

    New abbreviated syntax is introduced (focus function) for simple inline functions taking a single argument. An example is fn { ../@code }

    See 4.5.6 Inline Function Expressions

36. PR 603 

    The rules for reporting type errors during static analysis have been changed so that a processor has more freedom to report errors in respect of constructs that are evidently wrong, such as @price/@value, even though dynamic evaluation is defined to return an empty sequence rather than an error.

    See 2.4.6 Implausible Expressions

    See 4.6.4.6 Implausible Axis Steps

37. PR 606 

    Element and attribute tests of the form element(A|B) and attribute(A|B) are now allowed.

    See 3.2.7.2 Element Types

    See 3.2.7.3 Attribute Types

38. PR 691 

    Enumeration types are added as a new kind of ItemType, constraining the value space of strings.

    See 3.2.6 Enumeration Types

39. PR 728 

    The syntax record(*) is allowed; it matches any map.

    See 3.2.8.3 Record Types

40. PR 815 

    The coercion rules now allow conversion in either direction between xs:hexBinary and xs:base64Binary.

    See 3.4 Coercion Rules

41. PR 911 

    The coercion rules now allow any numeric type to be implicitly converted to any other, for example an xs:double is accepted where the required type is xs:decimal.

    See 3.4 Coercion Rules

42. PR 996 

    The value of a predicate in a filter expression can now be a sequence of integers.

    See 4.4 Filter Expressions

43. PR 1031 

    An otherwise operator is introduced: A otherwise B returns the value of A, unless it is an empty sequence, in which case it returns the value of B.

    See 4.15 Otherwise Expressions

44. PR 1071 

    In map constructors, the keyword map is now optional, so map { 0: false(), 1: true() } can now be written { 0: false(), 1: true() }, provided it is used in a context where this creates no ambiguity.

    See 4.13.1.1 Map Constructors

45. PR 1131 

    A positional variable can be defined in a for expression.

    See 4.12.1 For Expressions

    The type of a variable used in a for expression can be declared.

    See 4.12.1 For Expressions

    The type of a variable used in a let expression can be declared.

    See 4.12.2 Let Expressions

46. PR 1132 

    Choice item types (an item type allowing a set of alternative item types) are introduced.

    See 3.2.5 Choice Item Types

47. PR 1163 

    Filter expressions for maps and arrays are introduced.

    See 4.13.4 Filter Expressions for Maps and Arrays

48. PR 1181 

    The default namespace for elements and types can be set to the value ##any, allowing unprefixed names in axis steps to match elements with a given local name in any namespace.

    See 2.2.1 Static Context

    If the default namespace for elements and types has the special value ##any, then an unprefixed name in a NameTest acts as a wildcard, matching names in any namespace or none.

    See 4.6.4.2 Node Tests

49. PR 1197 

    The keyword fn is allowed as a synonym for function in function types, to align with changes to inline function declarations.

    See 3.2.8.1 Function Types

    In inline function expressions, the keyword function may be abbreviated as fn.

    See 4.5.6 Inline Function Expressions

50. PR 1212 

    XPath 3.0 included empty-sequence and item as reserved function names, and XPath 3.1 added map and array. This was unnecessary since these names never appear followed by a left parenthesis at the start of an expression. They have therefore been removed from the list. New keywords introducing item types, such as record and enum, have not been included in the list.

    See A.4 Reserved Function Names

51. PR 1217 

    Predicates in filter expressions for maps and arrays can now be numeric.

    See 4.13.4 Filter Expressions for Maps and Arrays

52. PR 1249 

    A for key/value clause is added to FLWOR expressions to allow iteration over maps.

    See 4.12.1 For Expressions

53. PR 1250 

    Several decimal format properties, including minus sign, exponent separator, percent, and per-mille, can now be rendered as arbitrary strings rather than being confined to a single character.

    See 2.2.1.2 Decimal Formats

54. PR 1265 

    The rules regarding the document-uri property of nodes returned by the fn:collection function have been relaxed.

    See 2.2.2 Dynamic Context

55. PR 1344 

    Parts of the static context that were there purely to assist in static typing, such as the statically known documents, were no longer referenced and have therefore been dropped.

    See 2.2.1 Static Context

    The static typing option has been dropped.

    See 2.3 Processing Model

    The static typing feature has been dropped.

    See 5 Conformance

56. PR 1361 

    The term atomic value has been replaced by atomic item.

    See 2.1.3 Values

57. PR 1384 

    If a type declaration is present, the supplied values in the input sequence are now coerced to the required type. Type declarations are now permitted in XPath as well as XQuery.

    See 4.16 Quantified Expressions

58. PR 1496 

    The context value static type, which was there purely to assist in static typing, has been dropped.

    See 2.2.1 Static Context

59. PR 1498 

    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.

    See 2.1 Terminology

    The EBNF notation has been extended to allow the constructs (A ++ ",") (one or more occurrences of A, comma-separated, and (A ** ",") (zero or more occurrences of A, comma-separated.

    See 2.1.1 Grammar Notation

    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.

    See A.1 EBNF

    See A.1.1 Notation

60. PR 1501 

    The coercion rules now apply recursively to the members of an array and the entries in a map.

    See 3.4 Coercion Rules

61. PR 1532 

    Four new axes have been defined: preceding-or-self, preceding-sibling-or-self, following-or-self, and following-sibling-or-self.

    See 4.6.4.1 Axes

62. PR 1577 

    The syntax record() is allowed; the only thing it matches is an empty map.

    See 3.2.8.3 Record Types

63. PR 1686 

    With the pipeline operator ->, the result of an expression can be bound to the context value before evaluating another expression.

    See 4.18 Pipeline operator

64. PR 1696 

    Parameter names may be included in a function signature; they are purely documentary.

    See 3.2.8.1 Function Types

65. PR 1703 

    Ordered maps are introduced.

    See 4.13.1 Maps

    The order of key-value pairs in the map constructor is now retained in the constructed map.

    See 4.13.1.1 Map Constructors

66. PR 1874 

    The coercion rules now reorder the entries in a map when the required type is a record type.

    See 3.4 Coercion Rules

67. PR 1898 

    The rules for subtyping of document node types have been refined.

    See 3.3.2.4.2 Subtyping Nodes: Document Nodes

68. PR 1991 

    Named record types used in the signatures of built-in functions are now available as standard in the static context.

    See 2.2.1 Static Context

69. PR 2026 

    The module feature is no longer an optional feature; processing of library modules is now required.

    See 5 Conformance

70. PR 2031 

    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.

    See 2.1.3 Values

    JNodes are introduced

    See 3.2.9 Generalized Node Types

71. PR 2055 

    Sequences, arrays, and maps can be destructured in a let expression to extract their components into multiple variables.

    See 4.12.2 Let Expressions

72. PR 2094 

    A general expression is allowed within a map constructor; this facilitates the creation of maps in which the presence or absence of particular keys is decided dynamically.

    See 4.13.1.1 Map Constructors

73. PR 2115 

    This section describes and formalizes a convention that was already in use, but not explicitly stated, in earlier versions of the specification.

    See 2.1.2 Expression Names