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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 K Change Log.
This is a draft prepared by the QT4CG (officially registered in W3C as the XSLT Extensions Community Group). Comments are invited.
The publications of this community group are dedicated to our co-chair, Michael Sperberg-McQueen (1954–2024).
This section discusses each of the basic kinds of expression. Each kind of expression has a name such as PathExpr, which is introduced on the left side of the grammar production that defines the expression. Since XQuery 4.0 is a composable language, each kind of expression is defined in terms of other expressions whose operators have a higher precedence. In this way, the precedence of operators is represented explicitly in the grammar.
The order in which expressions are discussed in this document does not reflect the order of operator precedence. In general, this document introduces the simplest kinds of expressions first, followed by more complex expressions. For the complete grammar, see Appendix [A XQuery 4.0 Grammar].
[Definition: A query consists of one or more modules.] If a query is executable, one of its modules has a Query Body containing an expression whose value is the result of the query. An expression is represented in the XQuery grammar by the symbol Expr.
Expr | ::= | (ExprSingle ++ ",") |
ExprSingle | ::= | FLWORExpr |
ExprSingle | ::= | FLWORExpr |
FLWORExpr | ::= | InitialClauseIntermediateClause* ReturnClause |
QuantifiedExpr | ::= | ("some" | "every") (QuantifierBinding ++ ",") "satisfies" ExprSingle |
SwitchExpr | ::= | "switch" SwitchComparand (SwitchCases | BracedSwitchCases) |
TypeswitchExpr | ::= | "typeswitch" "(" Expr ")" (TypeswitchCases | BracedTypeswitchCases) |
IfExpr | ::= | "if" "(" Expr ")" (UnbracedActions | BracedAction) |
TryCatchExpr | ::= | TryClauseCatchClause+ |
OrExpr | ::= | AndExpr ("or" AndExpr)* |
The XQuery 4.0 operator that has lowest precedence is the comma operator, which is used to combine two operands to form a sequence. As shown in the grammar, a general expression (Expr) can consist of multiple ExprSingle operands, separated by commas.
The name ExprSingle denotes an expression that does not contain a top-level comma operator (despite its name, an ExprSingle may evaluate to a sequence containing more than one item.)
The symbol ExprSingle is used in various places in the grammar where an expression is not allowed to contain a top-level comma. For example, each of the arguments of a function call must be a ExprSingle, because commas are used to separate the arguments of a function call.
After the comma, the expressions that have next lowest precedence are FLWORExpr,QuantifiedExpr, SwitchExpr, TypeswitchExpr, IfExpr, TryCatchExpr, and OrExpr. Each of these expressions is described in a separate section of this document.
XQuery provides node constructors that can create XML nodes within a query.
Constructors are provided for element, attribute, document, text, comment, and processing instruction nodes. Two kinds of constructors are provided: direct constructors, which use an XML-like notation that can incorporate enclosed expressions, and computed constructors, which use a notation based on enclosed expressions.
The rest of this section contains a conceptual description of the semantics of various kinds of constructor expressions. An XQuery implementation is free to use any implementation technique that produces the same result as the processing steps described here.
XQuery provides a versatile expression called a FLWOR expression that may contain multiple clauses. The FLWOR expression can be used for many purposes, including iterating over sequences, joining multiple documents, and performing grouping and aggregation. The name FLWOR, pronounced "flower", is suggested by the keywords for, let, where, order by, and return, which introduce some of the clauses used in FLWOR expressions (but this is not a complete list of such clauses.)
The overall syntax of a FLWOR expression is shown here, and relevant parts of the syntax are expanded in subsequent sections.
FLWORExpr | ::= | InitialClauseIntermediateClause* ReturnClause |
InitialClauseInitialClauseInitialClauseInitialClause | ::= | ForClause | LetClause | WindowClause |
ForClauseForClauseForClauseForClause | ::= | "for" (ForBinding ++ ",") |
LetClauseLetClauseLetClauseLetClause | ::= | "let" (LetBinding ++ ",") |
WindowClauseWindowClauseWindowClauseWindowClause | ::= | "for" (TumblingWindowClause | SlidingWindowClause) |
IntermediateClauseIntermediateClauseIntermediateClauseIntermediateClause | ::= | InitialClause | WhereClause | WhileClause | GroupByClause | OrderByClause | CountClause |
WhereClauseWhereClauseWhereClauseWhereClause | ::= | "where" ExprSingle |
WhileClauseWhileClauseWhileClauseWhileClause | ::= | "while" ExprSingle |
GroupByClauseGroupByClauseGroupByClauseGroupByClause | ::= | "group" "by" (GroupingSpec ++ ",") |
OrderByClauseOrderByClauseOrderByClauseOrderByClause | ::= | "stable"? "order" "by" (OrderSpec (++ "," OrderSpec)* |
CountClauseCountClauseCountClauseCountClause | ::= | "count" VarName |
ReturnClauseReturnClauseReturnClauseReturnClause | ::= | "return" ExprSingle |
The semantics of FLWOR expressions are based on a concept called a tuple stream. [Definition: A tuple stream is an ordered sequence of zero or more tuples.] [Definition: A tuple is a set of zero or more named variables, each of which is bound to a value that is an XDM instance.] Each tuple stream is homogeneous in the sense that all its tuples contain variables with the same names and the same static types. The following example illustrates a tuple stream consisting of four tuples, each containing three variables named $x, $y, and $z:
($x = 1003, $y = "Fred", $z = <age>21</age>) ($x = 1017, $y = "Mary", $z = <age>35</age>) ($x = 1020, $y = "Bill", $z = <age>18</age>) ($x = 1024, $y = "John", $z = <age>29</age>)
Note:
In this section, tuple streams are represented as shown in the above example. Each tuple is on a separate line and is enclosed in parentheses, and the variable bindings inside each tuple are separated by commas. This notation does not represent XQuery syntax, but is simply a representation of a tuple stream for the purpose of defining the semantics of FLWOR expressions.
Tuples and tuple streams are not part of the data model. They exist only as conceptual intermediate results during the processing of a FLWOR expression.
Conceptually, the first clause generates a tuple stream. Each clause between the first clause and the return clause takes the tuple stream generated by the previous clause as input and generates a (possibly different) tuple stream as output. The return clause takes a tuple stream as input and, for each tuple in this tuple stream, generates an XDM instance; the final result of the FLWOR expression is the ordered concatenation of these XDM instances.
The initial clause in a FLWOR expression may be a for, let, or window clause. Intermediate clauses may be for, let, window, count, where, group by, or order by clauses. These intermediate clauses may be repeated as many times as desired, in any order. The final clause of the FLWOR expression must be a return clause. The semantics of the various clauses are described in the following sections.
OrderByClause | ::= | "stable"? "order" "by" (OrderSpec (++ "," OrderSpec)* |
OrderSpec | ::= | ExprSingleOrderModifier |
ExprSingle | ::= | FLWORExpr |
OrderModifier | ::= | ("ascending" | "descending")? ("empty" ("greatest" | "least"))? ("collation" URILiteral)? |
URILiteral | ::= | StringLiteral |
StringLiteral | ::= | AposStringLiteral | QuotStringLiteral |
| /* ws: explicit */ |
The purpose of an order by clause is to impose a value-based ordering on the tuples in the tuple stream. The output tuple stream of the order by clause contains the same tuples as its input tuple stream, but the tuples may be in a different order.
An order by clause contains one or more ordering specifications, called orderspecs, as shown in the grammar. For each tuple in the input tuple stream, the orderspecs are evaluated, using the variable bindings in that tuple. The relative order of two tuples is determined by comparing the values of their orderspecs, working from left to right until a pair of unequal values is encountered. If an orderspec specifies a collation, that collation is used in comparing values of type xs:string, xs:anyURI, or types derived from them (otherwise, the default collation is used in comparing values of these types). If an orderspec specifies a collation by a relative URI, that relative URI is resolved to an absolute URI using the Static Base URI. If an orderspec specifies a collation that is not found in statically known collations, an error is raised [err:XQST0076].
The process of evaluating and comparing the orderspecs is based on the following rules:
Atomization is applied to the result of the expression in each orderspec. If the result of atomization is neither a single atomic item nor an empty sequence, a type error is raised [err:XPTY0004].
For the purpose of determining their relative position in the ordering sequence, the greater-than relationship between two orderspec values W and V is defined as follows:
When the orderspec specifies empty least, the following rules are applied in order:
If V is an empty sequence and W is not an empty sequence, then Wgreater-thanV is true.
If V is NaN and W is neither NaN nor an empty sequence, then Wgreater-thanV is true.
If V and W are both instances of xs:string, xs:anyURI, or xs:untypedAtomic, they are compared using the function fn:compare(V, W, C) where C is the requested collation, defaulting to the default collation from the static context.
If fn:compare(V, W, C) is less than zero, then Wgreater-thanV is true; otherwise Wgreater-thanV is false.
If V and W are both instances of xs:numeric, they are compared using the function fn:compare(V, W).
If fn:compare(V, W) is less than zero, then Wgreater-thanV is true; otherwise Wgreater-thanV is false.
If none of the above rules apply, then:
If W gt V is true, then Wgreater-thanV is true; otherwise Wgreater-thanV is false.
When the orderspec specifies empty greatest, the following rules are applied in order:
If W is an empty sequence and V is not an empty sequence, then Wgreater-thanV is true.
If W is NaN and V is neither NaN nor an empty sequence, then Wgreater-thanV is true.
If V and W are both instances of xs:string, xs:anyURI, or xs:untypedAtomic, they are compared using the function fn:compare(V, W, C) where C is the requested collation, defaulting to the default collation from the static context.
If fn:compare(V, W, C) is less than zero, then Wgreater-thanV is true; otherwise Wgreater-thanV is false.
If V and W are both instances of xs:numeric, they are compared using the function fn:compare(V, W).
If fn:compare(V, W) is less than zero, then Wgreater-thanV is true; otherwise Wgreater-thanV is false.
If none of the above rules apply, then:
If W gt V is true, then Wgreater-thanV is true; otherwise Wgreater-thanV is false.
When the orderspec specifies neither empty least nor empty greatest, the default order for empty sequences in the static context determines whether the rules for empty least or empty greatest are used.
If T1 and T2 are two tuples in the input tuple stream, and V1 and V2 are the first pair of values encountered when evaluating their orderspecs from left to right for which one value is greater-than the other (as defined above), then:
If V1 is greater-thanV2: If the orderspec specifies descending, then T1 precedes T2 in the output tuple stream; otherwise, T2 precedes T1 in the output tuple stream.
If V2 is greater-thanV1: If the orderspec specifies descending, then T2 precedes T1 in the output tuple stream; otherwise, T1 precedes T2 in the output tuple stream.
If neither V1 nor V2 is greater-than the other for any pair of orderspecs for tuples T1 and T2, the following rules apply.
If stable is specified, the original order of T1 and T2 is preserved in the output tuple stream.
If stable is not specified, the order of T1 and T2 in the output tuple stream is implementation-dependent.
Note:
If two orderspecs return the special floating-point values positive and negative zero, neither of these values is greater-than the other, since +0.0 gt -0.0 and -0.0 gt +0.0 are both false.
Examples:
This example illustrates the effect of an order by clause on a tuple stream. The keyword stable indicates that, when two tuples have equal sort keys, their order in the input tuple stream is preserved.
Input tuple stream:
($license = "PFQ519", $make = "Ford", $value = 16500) ($license = "HAJ865", $make = "Honda", $value = 22750) ($license = "NKV473", $make = "Ford", $value = 21650) ($license = "RCM922", $make = "Dodge", $value = 11400) ($license = "ZBX240", $make = "Ford", $value = 16500) ($license = "KLM030", $make = "Dodge", $value = () )
order by clause:
stable order by $make, $value descending empty least
Output tuple stream:
($license = "RCM922", $make = "Dodge", $value = 11400) ($license = "KLM030", $make = "Dodge", $value = () ) ($license = "NKV473", $make = "Ford", $value = 21650) ($license = "PFQ519", $make = "Ford", $value = 16500) ($license = "ZBX240", $make = "Ford", $value = 16500) ($license = "HAJ865", $make = "Honda", $value = 22750)
The following example shows how an order by clause can be used to sort the result of a query, even if the sort key is not included in the query result. This query returns employee names in descending order by salary, without returning the actual salaries:
for $e in $employees order by $e/salary descending return $e/name
Note:
If a collation name is specified, it must be supplied as a literal string; it cannot be computed dynamically. Two possible workarounds are to use the fn:sort function or the fn:collation-key function.
Using fn:sort the expression
for $b in $books/book[price < 100] order by $b/title return $b
can be replaced with the following, which uses a dynamically-chosen collation:
sort(
$books/book[price < 100],
$collation,
function($book) { $book/title }
)Alternatively, it is possible to compute collation keys using a dynamically-chosen collation, and sort on the values of the collation keys:
for $b in $books/book[price < 100] order by collation-key($b/title, $collation) return $b
Note however that the fn:collation-key function might not work for all collations.
A query can be assembled from one or more fragments called modules. [Definition: A module is a fragment of XQuery code that conforms to the Module grammar and can independently undergo the static analysis phase described in 2.3.3 Expression Processing. Each module is either a main module or a library module.]
[Definition: A main module consists of a Prolog followed by a Query Body.] A query has exactly one main module. In a main module, the Query Body is evaluated with respect to the static and dynamic contexts of the main module in which it is found, and its value is the result of the query.
[Definition: 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.] A library module cannot be evaluated directly; instead, it provides function and variable declarations that can be imported into other modules.
The XQuery syntax does not allow a module to contain both a module declaration and a Query Body.
[Definition: A Prolog is a series of declarations and imports that define the processing environment for the module that contains the Prolog.] Each declaration or import is followed by a semicolon. A Prolog is organized into two parts.
The first part of the Prolog consists of setters, imports, namespace declarations, and default namespace declarations. [Definition: Setters are declarations that set the value of some property that affects query processing, such as construction mode or default collation.] Namespace declarations and default namespace declarations affect the interpretation of lexical QNames within the query. Imports are used to import definitions from schemas and modules. [Definition: The target namespace of a module is the namespace of the objects (such as elements or functions) that it defines. ]
The second part of the Prolog consists of declarations of variables, functions, and options. These declarations appear at the end of the Prolog because they may be affected by declarations and imports in the first part of the Prolog.
[Definition: The Query Body, if present, consists of an expression that defines the result of the query.] Evaluation of expressions is described in 4 Expressions. A module can be evaluated only if it has a Query Body.
Function definitions in the static context may now have optional parameters, provided this does not cause ambiguity across multiple function definitions with the same name. Optional parameters are given a default value, which can be any expression, including one that depends on the context of the caller (so an argument can default to the context value).
In addition to the system functions, XQuery allows users to declare functions of their own. A function declaration declares a family of functions having the same name and similar parameters. The declaration specifies the name of the function, the names and datatypes of the parameters, and the datatype of the result. All datatypes are specified using the syntax described in 3 Types.
Including a function declaration in the query causes a corresponding function definition to be added to the statically known function definitions of the static context. The associated functions also become available in the dynamically known function definitions of the dynamic context.
FunctionDecl | ::= | "declare" Annotation? "function" EQName "(" ParamListWithDefaults? ")" TypeDeclaration? (FunctionBody | "external") |
| /* xgc: reserved-function-names */ | ||
Annotation | ::= | "%" EQName ("(" (AnnotationValue ++ ",") ")")? |
EQName | ::= | QName | URIQualifiedName |
ParamListWithDefaults | ::= | (ParamWithDefault ++ ",") |
ParamWithDefault | ::= | VarNameAndType (":=" ExprSingle)? |
VarNameAndType | ::= | "$" EQNameTypeDeclaration? |
EQName | ::= | QName | URIQualifiedName |
TypeDeclaration | ::= | "as" SequenceType |
SequenceType | ::= | ("empty-sequence" "(" ")") |
ExprSingle | ::= | FLWORExpr |
FunctionBody | ::= | EnclosedExpr |
EnclosedExpr | ::= | "{" Expr? "}" |
A function declaration specifies whether the implementation of the function is user-defined or external.
In addition to user-defined functions and external functions, XQuery 4.0 allows anonymous functions to be declared in the body of a query using inline function expressions.
The following example illustrates the declaration and use of a local function that accepts a sequence of employee elements, summarizes them by department, and returns a sequence of dept elements.
declare function local:summary($emps as element(employee)*) as element(dept)* {
for $no in distinct-values($emps/deptno)
let $emp := $emps[deptno = $no]
return <dept>
<deptno>{ $no }</deptno>
<headcount>{ count($emp) }</headcount>
<payroll>{ sum($emp/salary) }</payroll>
</dept>
};
local:summary(doc("acme_corp.xml")//employee[location = "Denver"])The grammar of XQuery 4.0 uses the same simple Extended Backus-Naur Form (EBNF) notation as [XML 1.0] with the following differences.
The notation XYZ ** "," indicates a sequence of zero or more occurrences of XYZ, with a single comma between adjacent occurrences.
The notation XYZ ++ "," indicates a sequence of one or more occurrences of XYZ, with a single comma between adjacent occurrences.
All named symbols have a name that begins with an uppercase letter.
It adds a notation for referring to productions in external specifications.
Comments or extra-grammatical constraints on grammar productions are between '/*' and '*/' symbols.
A 'xgc:' prefix is an extra-grammatical constraint, the details of which are explained in A.1.2 Extra-grammatical Constraints
A 'ws:' prefix explains the whitespace rules for the production, the details of which are explained in A.3.5 Whitespace Rules
A 'gn:' prefix means a 'Grammar Note', and is meant as a clarification for parsing rules, and is explained in A.1.3 Grammar Notes. These notes are not normative.
The terminal symbols for this grammar include the quoted strings used in the production rules below, and the terminal symbols defined in section A.3.1 Terminal Symbols. The grammar is a little unusual in that parsing and tokenization are somewhat intertwined: for more details see A.3 Lexical structure.
The EBNF notation is described in more detail in A.1.1 Notation.
This section describes how an XQuery 4.0 text is tokenized prior to parsing.
All keywords are case sensitive. Keywords are not reserved—that is, any lexical QName may duplicate a keyword except as noted in A.4 Reserved Function Names.
Tokenizing an input string is a process that follows the following rules:
[Definition: An ordinary production rule is a production rule in A.1 EBNF that is not annotated ws:explicit.]
[Definition: A literal terminal is a token appearing as a string in quotation marks on the right-hand side of an ordinary production rule.]
Note:
Strings that appear in other production rules do not qualify. For example, "]]>" is not a literal terminal, because it appears only in the rule CDataSection, which is not an ordinary production rule; similarly BracedURILiteral does not qualify because it appears only in URIQualifiedName, and "0x" does not qualify because it appears only in HexIntegerLiteral.
The literal terminals in XQuery 4.0 are: !!=#$%()*+,...///::::=;<<<<===!>=>=?>>>=>>????[@[]{|||}×÷-->allowingancestorancestor-or-selfandarrayasascendingatattributebase-uriboundary-spacebycasecastcastablecatchchildcollationcommentconstructioncontextcopy-namespacescountdecimal-formatdecimal-separatordeclaredefaultdescendantdescendant-or-selfdescendingdigitdivdocumentdocument-nodeelementelseemptyempty-sequenceencodingendenumeqeveryexceptexponent-separatorexternalfalsefixedfnfollowingfollowing-or-selffollowing-siblingfollowing-sibling-or-selfforfunctiongegreatestgroupgrouping-separatorgtidivifimportininfinityinheritinstanceintersectisitemitemskeykeyslaxleleastletltmapmemberminus-signmodmodulenamespacenamespace-nodeNaNnenextno-inheritno-preservenodeofonlyoptionororderorderedorderingotherwisepairsparentpattern-separatorper-millepercentprecedingpreceding-or-selfpreceding-sibling-or-selfpreservepreviousprocessing-instructionrecordreturnsatisfiesschemaschema-attributeschema-elementselfslidingsomestablestartstrictstripswitchtextthentotreattruetrytumblingtypetypeswitchunionunorderedvalidatevaluevaluesvariableversionwhenwherewhilewindowxqueryzero-digit
[Definition: 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.]
The variable terminals in XQuery 4.0 are: BinaryIntegerLiteralCDataSectionDecimalLiteralDirCommentConstructorDirElemConstructorDirPIConstructorDoubleLiteralHexIntegerLiteralIntegerLiteralNCNamePragmaQNameStringConstructorStringLiteralStringTemplateURIQualifiedNameWildcard
[Definition: A complex terminal is a variable terminal whose production rule references, directly or indirectly, an ordinary production rule.]
The complex terminals in XQuery 4.0 are: DirElemConstructorPragmaStringConstructorStringTemplate
Note:
The significance of complex terminals is that at one level, a complex terminal is treated as a single token, but internally it may contain arbitrary expressions that must be parsed using the full EBNF grammar.
Tokenization is the process of splitting the supplied input string into a sequence of terminals, where each terminal is either a literal terminal or a variable terminal (which may itself be a complex terminal). Tokenization is done by repeating the following steps:
Starting at the current position, skip any whitespace and comments.
If the current position is not the end of the input, then return the longest literal terminal or variable terminal that can be matched starting at the current position, regardless whether this terminal is valid at this point in the grammar. If no such terminal can be identified starting at the current position, or if the terminal that is identified is not a valid continuation of the grammar rules, then a syntax error is reported.
Note:
Here are some examples showing the effect of the longest token rule:
The expression map{a:b} is a syntax error. Although there is a tokenization of this string that satisfies the grammar (by treating a and b as separate expressions), this tokenization does not satisfy the longest token rule, which requires that a:b is interpreted as a single QName.
The expression 10 div3 is a syntax error. The longest token rule requires that this be interpreted as two tokens ("10" and "div3") even though it would be a valid expression if treated as three tokens ("10", "div", and "3").
The expression $x-$y is a syntax error. This is interpreted as four tokens, ("$", "x-", "$", and "y").
Note:
The lexical production rules for variable terminals have been designed so that there is minimal need for backtracking. For example, if the next terminal starts with "0x", then it can only be either a HexIntegerLiteral or an error; if it starts with "`" (and not with "```") then it can only be a StringTemplate or an error. Direct element constructors in XQuery, however, need special treatment, described below.
This convention, together with the rules for whitespace separation of tokens (see A.3.2 Terminal Delimitation) means that the longest-token rule does not normally result in any need for backtracking. For example, suppose that a variable terminal has been identified as a StringTemplate by examining its first few characters. If the construct turns out not to be a valid StringTemplate, an error can be reported without first considering whether there is some shorter token that might be returned instead.
Tokenization requires special care when the current character is U+003C (LESS-THAN SIGN, <) :
If the following character is U+003D (EQUALS SIGN, =) then the token can be identified unambiguously as the operator <=.
If the following character is U+003C (LESS-THAN SIGN, <) then the token can be identified unambiguously as the operator <<.
If the following character is U+0021 (EXCLAMATION MARK, !) then the token can be identified unambiguously as being a DirCommentConstructor (a CDataSection, which also starts with <! can appear only within a direct element constructor, not as a free-standing token).
If the following character is U+003F (QUESTION MARK, ?) , then the token is identified as a DirPIConstructor if and only if a match for the relevant production ("<?" PITarget (S DirPIContents)? "?>") is found. If there is no such match, then the string "<?" is identified as a less-than operator followed by a lookup operator.
If the following character is a NameStartChar then the token is identified as a DirElemConstructor if and only if a match for the leading part of a DirElemConstructor is found: specifically if a substring starting at the U+003C (LESS-THAN SIGN, <) character matches one of the following regular expressions:
^<\i\c*\s*>(as in<element>...)^<\i\c*\s*/>(as in<element/>)^<\i\c*\s+\i\c*\s*=(as in<element att=...)
If the content matches one of these regular expressions but further analysis shows that the subsequent content does not satisfy the DirElemConstructor production, then a static error is reported.
If the content does not match any of these regular expressions then the token is identified as the less-than operator <.
If the following character is any other character then the token can be identified unambiguously as the less-than operator <.
This analysis is done without regard to the syntactic context of the U+003C (LESS-THAN SIGN, <) character. However, a tokenizer may avoid looking for a DirPIConstructor or DirElemConstructor if it knows that such a constructor cannot appear in the current syntactic context.
Note:
The rules here are described much more precisely than in XQuery 3.1, and the results in edge cases might be incompatible with some XQuery 3.1 processors.
Note:
To avoid potential confusion, simply add whitespace after any less-than operator.
Tokenization unambiguously identifies the boundaries of the terminals in the input, and this can be achieved without backtracking or lookahead. However, tokenization does not unambiguously classify each terminal. For example, it might identify the string "div" as a terminal, but it does not resolve whether this is the operator symbol div, or an NCName or QName used as a node test or as a variable or function name. Classification of terminals generally requires information about the grammatical context, and in some cases requires lookahead.
Note:
Operationally, classification of terminals may be done either in the tokenizer or the parser, or in some combination of the two. For example, according to the EBNF, the expression "parent::x" is made up of three tokens, "parent", "::", and "x". The name "parent" can be classified as an axis name as soon as the following token "::" is recognized, and this might be done either in the tokenizer or in the parser. (Note that whitespace and comments are allowed both before and after "::".)
In the case of a complex terminal, identifying the end of the complex terminal typically involves invoking the parser to process any embedded expressions. Tokenization, as described here, is therefore a recursive process. But other implementations are possible.
Note:
Previous versions of this specification included the statement: When tokenizing, the longest possible match that is consistent with the EBNF is used.
Different processors are known to have interpreted this in different ways. One interpretation, for example, was that the expression 10 div-3 should be split into four tokens (10, div, -, 3) on the grounds that any other tokenization would give a result that was inconsistent with the EBNF grammar. Other processors report a syntax error on this example.
This rule has therefore been rewritten in version 4.0. Tokenization is now entirely insensitive to the grammatical context; div-3 is recognized as a single token even though this results in a syntax error. For some implementations this may mean that expressions that were accepted in earlier releases are no longer accepted in 4.0.
A more subtle example is: (. <?b ) cast as xs:integer?> 0) in which <?b ) cast as xs:integer?> is recognized as a single token (a direct processing instruction constructor) even though such a token cannot validly appear in this grammatical context.
XQuery 4.0 expressions consist of terminal symbols and symbol separators.
Literal and variable terminal symbols are of two kinds: delimiting and non-delimiting.
[Definition: The delimiting terminal symbols are: !!=##)$%((#)**:+,--->->...////>::*:::=;<<!--<![CDATA[</<<<=<?==!>=>=?>>>=>>??>???[@[]]]>]```````[`{{{{|||}}`}}×÷AposStringLiteralBracedURILiteral<#)(#QuotStringLiteralS///StringLiteral ]
[Definition: The non-delimiting terminal symbols are: allowingancestorancestor-or-selfandarrayasascendingatattributebase-uriboundary-spacebycasecastcastablecatchchildcollationcommentconstructioncontextcopy-namespacescountdecimal-formatdecimal-separatordeclaredefaultdescendantdescendant-or-selfdescendingdigitdivdocumentdocument-nodeelementelseemptyempty-sequenceencodingendenumeqeveryexceptexponent-separatorexternalfalsefixedfnfollowingfollowing-or-selffollowing-siblingfollowing-sibling-or-selfforfunctiongegreatestgroupgrouping-separatorgtidivifimportininfinityinheritinstanceintersectisitemitemskeykeyslaxleleastletltmapmemberminus-signmodmodulenamespacenamespace-nodeNaNnenextno-inheritno-preservenodeofonlyoptionororderorderedorderingotherwisepairsparentpattern-separatorper-millepercentprecedingpreceding-or-selfpreceding-sibling-or-selfpreservepreviousprocessing-instructionrecordreturnsatisfiesschemaschema-attributeschema-elementselfslidingsomestablestartstrictstripswitchtextthentotreattruetrytumblingtypetypeswitchunionunorderedvalidatevaluevaluesvariableversionwhenwherewhilewindowxqueryzero-digitascendingBinaryIntegerLiteralDecimalLiteraldescendingDoubleLiteralexternalgreatestHexIntegerLiteralIntegerLiteralleastNCNameQNameURIQualifiedName ]
[Definition: 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.]
As a consequence of the longest token rule (see A.3 Lexical structure), one or more symbol separators are required between two consecutive terminal symbols T and U (where T precedes U) when any of the following is true:
T and U are both non-delimiting terminal symbols.
T is a QName or an NCName and U is "." or "-".
T is a numeric literal and U is ".", or vice versa.
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 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.
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).
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.
An array is a function item that associates a set of positions, represented as positive integer keys, with values.
The value associated with a given key is called the associated value of the key.
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].
An atomic type is a simple schema type whose {variety}XS11-1 is atomic.
Atomization of a sequence is defined as the result of invoking the fn:data function, as defined in Section 2.1.4 fn:dataFO.
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 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. 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. 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.
An axis step returns a sequence of nodes that are reachable from a starting node via a specified axis. Such a step has two parts: an axis, which defines the "direction of movement" for the step, and a node test, which selects nodes based on their kind, name, and/or type annotation .
A base URI declaration specifies the Static Base URI property. The Static Base URI property is used when resolving relative URI references.
In the operator mapping tables, the term binary refers to the types xs:hexBinary and xs:base64Binary.
In a for clause, when an expression is preceded by the keyword in, the value of that expression is called a binding collection.
In a window clause, when an expression is preceded by the keyword in, the value of that expression is called a binding sequence.
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. This component controls the processing of boundary whitespace by direct element constructors, as described in 4.12.1.4 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   or by CDataSections are not considered to be whitespace characters.
A character reference is an XML-style reference to a [Unicode] character, identified by its decimal or hexadecimal codepoint.
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.
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.
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 stringsFO.
One way to construct a sequence is by using the comma operator, which evaluates each of its operands and concatenates the resulting sequences, in order, into a single result sequence.
A complex terminal is a variable terminal whose production rule references, directly or indirectly, an ordinary production rule.
A computed element constructor creates an element node, allowing both the name and the content of the node to be computed.
A construction declaration sets the construction mode in the static context, overriding any implementation-defined default.
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.
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?.
In an enclosed expression, the optional expression enclosed in curly brackets is called the content expression.
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.
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.
The context position is the position of the context value within the series of values currently being processed.
The context size is the number of values in the series of values currently being processed.
The context value is the value currently being processed.
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. This component controls the namespace bindings that are 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. 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.
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 [XQuery and XPath Data Model (XDM) 4.0].
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(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. 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. 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.
A default collation declaration sets the value of the default collation in the static context, overriding any implementation-defined default.
Default collection. This is the sequence of items that would result from calling the fn:collection function with no arguments.
Default function namespace. This is either a namespace URI, or absentDM. The namespace URI, if present, is used for any unprefixed QName appearing in a position where a function name is expected.
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. 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. 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. 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 URI collection. This is the sequence of URIs that would result from calling the fn:uri-collection function with no arguments.
The delimiting terminal symbols are: !!=##)$%((#)**:+,--->->...////>::*:::=;<<!--<![CDATA[</<<<=<?==!>=>=?>>>=>>??>???[@[]]]>]```````[`{{{{|||}}`}}×÷AposStringLiteralBracedURILiteral<#)(#QuotStringLiteralS///StringLiteral
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.
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(M) is a character used in the picture string to represent an optional digit; the default value is U+0023 (NUMBER SIGN, #) .
A direct element constructor is a form of element constructor in which the name of the constructed element is a constant.
Informally, document order is the order in which nodes appear in the XML serialization of a document.
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.
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.
A dynamic error is an error that must be detected during the dynamic evaluation phase and may be detected during the static analysis phase.
The dynamic evaluation phase is the phase during which the value of an expression is computed.
A dynamic function call consists of a base expression that returns the function and a parenthesized list of zero or more arguments (argument expressions or ArgumentPlaceholders).
A dynamic function call is an expression that is evaluated by calling a function item, which is typically obtained dynamically.
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.
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 7.3.1 fn:booleanFO.
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.
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.
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.
A sequence containing zero items is called an empty sequence.
An enclosed expression is an instance of the EnclosedExpr production, which allows an optional expression within curly brackets.
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".
Each key / value pair in a map is called an entry.
An EnumerationType accepts a fixed set of string values.
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.
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.
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. 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.
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(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) .
The expression context for a given expression consists of all the information that can affect the result of the expression.
An extension expression is an expression whose semantics are implementation-defined.
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.
A filter expression 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.
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.
The first three components of the dynamic context (context value, context position, and context size) are called the focus of the expression.
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()*.
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 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.
A function definition contains information used to evaluate a static function call, including the name, parameters, and return type of the function.
A function item is an item that can be called using a dynamic function call.
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.
In the operator mapping tables, the term Gregorian refers to the types xs:gYearMonth, xs:gYear, xs:gMonthDay, xs:gDay, and xs:gMonth.
The atomized value of a grouping variable is called a grouping key.
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, ,) .
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.
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 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 Handling).
Certain expressions, while not erroneous, are classified as being implausible, because they achieve no useful effect.
Implementation-defined indicates an aspect that may differ between implementations, but must be specified by the implementer for each particular implementation.
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. 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(R) is the string used to represent the double value infinity (INF); the default value is the string "Infinity"
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.
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.
An inline function expression, when evaluated, creates an anonymous function defined directly in the inline function expression.
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. 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. This is a mapping from expanded QName to named item types.
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 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 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. This is a mapping from expanded QName to type. 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.
An item is either an atomic item, a node, or a function item.
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.
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.
An alternative form of a node test called a kind test can select nodes based on their kind, name, and type annotation.
A lexical QName is a name that conforms to the syntax of the QName production
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.
A literal is a direct syntactic representation of an atomic item.
A literal terminal is a token appearing as a string in quotation marks on the right-hand side of an ordinary production rule.
A main module consists of a Prolog followed by a Query Body.
A map is a function that associates a set of keys with values, resulting in a collection of key / value pairs.
The mapping arrow operator=!> applies a function to each item in a sequence.
MAY means that an item is truly optional.
The values of an array are called its members.
minus-sign(R) is the string used to mark negative numbers; the default value is U+002D (HYPHEN-MINUS, -) .
A module is a fragment of XQuery code that conforms to the Module grammar and can independently undergo the static analysis phase described in 2.3.3 Expression Processing. Each module is either a main module or a library module.
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.
The Module Feature allows a query Prolog to contain a Module Import and allows library modules to be created.
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 means that the item is an absolute requirement of the specification.
MUST NOT means that the item is an absolute prohibition of the specification.
A named function reference 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.
A named item type is an ItemType identified by an expanded QName.
When an expression is used to specify the name of a constructed node, that expression is called the name expression of the constructor.
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.
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.
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.
A node test that consists only of an EQName or a Wildcard is called a name test.
NaN(R) is the string used to represent the double value NaN (not a number); the default value is the string "NaN"
A node is an instance of one of the node kinds defined in Section 5 NodesDM.
A node test is a condition on the name, kind (element, attribute, text, document, comment, or processing instruction), and/or type annotation of a node. A node test determines which nodes contained by an axis are selected by a step.
The non-delimiting terminal symbols are: allowingancestorancestor-or-selfandarrayasascendingatattributebase-uriboundary-spacebycasecastcastablecatchchildcollationcommentconstructioncontextcopy-namespacescountdecimal-formatdecimal-separatordeclaredefaultdescendantdescendant-or-selfdescendingdigitdivdocumentdocument-nodeelementelseemptyempty-sequenceencodingendenumeqeveryexceptexponent-separatorexternalfalsefixedfnfollowingfollowing-or-selffollowing-siblingfollowing-sibling-or-selfforfunctiongegreatestgroupgrouping-separatorgtidivifimportininfinityinheritinstanceintersectisitemitemskeykeyslaxleleastletltmapmemberminus-signmodmodulenamespacenamespace-nodeNaNnenextno-inheritno-preservenodeofonlyoptionororderorderedorderingotherwisepairsparentpattern-separatorper-millepercentprecedingpreceding-or-selfpreceding-sibling-or-selfpreservepreviousprocessing-instructionrecordreturnsatisfiesschemaschema-attributeschema-elementselfslidingsomestablestartstrictstripswitchtextthentotreattruetrytumblingtypetypeswitchunionunorderedvalidatevaluevaluesvariableversionwhenwherewhilewindowxqueryzero-digitascendingBinaryIntegerLiteralDecimalLiteraldescendingDoubleLiteralexternalgreatestHexIntegerLiteralIntegerLiteralleastNCNameQNameURIQualifiedName
When referring to a type, the term numeric denotes the types xs:integer, xs:decimal, xs:float, and xs:double which are all member types of the built-in union type xs:numeric.
A predicate whose predicate expression returns a value of type xs:numeric+ is called a numeric predicate.
For each operator and valid combination of operand types, the operator mapping tables specify a result type and an expression that invokes an operator function; the operator function implements the semantics of the operator for the given types.
An option declaration declares an option that affects the behavior of a particular implementation. Each option consists of an identifying EQName and a StringLiteral.
An ordinary production rule is a production rule in A.1 EBNF that is not annotated ws:explicit.
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.
A static or dynamic function call is a partial function application if one or more arguments is an ArgumentPlaceholder.
A partially applied function is a function created by partial function application.
A path expression consists of a series of one or more steps, separated by / or //, and optionally beginning with / or //. A path expression is typically used to locate nodes within trees.
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(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(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, ‰) .
The pipeline operator-> evaluates an expression and binds the result to the context value before evaluating another expression.
A positional variable is a variable that is preceded by the keyword at.
A pragma is denoted by the delimiters (# and #), and consists of an identifying EQName followed by implementation-defined content.
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.
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 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.
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.
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.
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.
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.
A Prolog is a series of declarations and imports that define the processing environment for the module that contains the Prolog.
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.
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.
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.
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
A query consists of one or more modules.
The Query Body, if present, consists of an expression that defines the result of the query.
A reserved namespace is a namespace that must not be used in the name of a function declaration.
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).
The node ordering that is the reverse of document order is called reverse document order.
Two atomic items K1 and K2 have the same key value if fn:atomic-equal(K1, K2) returns true, as specified in Section 13.2.1 fn:atomic-equalFO
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).
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.
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.
A sequence is an ordered collection of zero or more items.
The sequence arrow operator=> applies a function to a supplied sequence.
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.
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.
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 compares a value with an expected sequence type.
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].
The Serialization Feature provides means for serializing the result of a query as specified in 2.3.5 Serialization.
Setters are declarations that set the value of some property that affects query processing, such as construction mode or default collation.
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.
A sequence containing exactly one item is called a singleton.
A singleton focus is a fixed focus in which the context value is a singleton item.
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. 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. 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. This is a set of function definitions.
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.
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. This is an absolute URI, used to resolve relative URIs during static analysis.
The static context of an expression is the information that is available during static analysis of the expression, prior to its evaluation.
An error that can be detected during the static analysis phase, and is not a type error, is a static error.
A static function call consists of an EQName followed by a parenthesized list of zero or more arguments.
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.
A step is a part of a path expression that generates a sequence of items and then filters the sequence by zero or more predicates. The value of the step consists of those items that satisfy the predicates, working from left to right. A step may be either an axis step or a postfix expression.
A String Constructor creates a string from literal text and interpolated expressions.
The string value of a node is a string and can be extracted by applying the Section 2.1.3 fn:stringFO function to the node.
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, {}.
The empty array, [].
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.
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.
The use of a value that has a dynamic type that is a subtype of the expected type is known as subtype substitution.
Each rule in the grammar defines one symbol, using the following format:
symbol ::= expression
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 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.
The target namespace of a module is the namespace of the objects (such as elements or functions) that it defines.
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.
A tuple is a set of zero or more named variables, each of which is bound to a value that is an XDM instance.
A tuple stream is an ordered sequence of zero or more tuples.
Each element node and attribute node in an XDM instance has a type annotation (described in Section 2.8 Schema InformationDM). The type annotation of a node is a reference to a schema type.
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.
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.
The typed value of a node is a sequence of atomic items and can be extracted by applying the Section 2.1.4 fn:dataFO function to the node.
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.
Under certain circumstances, an atomic item can be promoted from one type to another.
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 functions are functions that contain a function body, which provides the implementation of the function as a content expression.
In the data model, a value is always a sequence.
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.
A variable reference is an EQName preceded by a $-sign.
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. This is a mapping from expanded QName to value. 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.
A version declaration can identify the applicable XQuery syntax and semantics for a module, as well as its encoding.
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.
A whitespace character is any of the characters defined by [http://www.w3.org/TR/REC-xml/#NT-S].
In these rules, if MU and NU are NameTestUnions, then MUwildcard-matchesNU is true if every name that matches MU also matches NU.
A window is a sequence of consecutive items drawn from the binding sequence.
The term XDM instance is used, synonymously with the term value, to denote an unconstrained sequence of items.
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.
An XQuery 1.0 Processor processes a query according to the XQuery 1.0 specification.
An XQuery 3.0 Processor processes a query according to the XQuery 3.0 specification.
An XQuery 3.1 Processor processes a query according to the XQuery 3.1 specification.
An XQuery 4.0 Processor processes a query according to the XQuery 4.0 specification.
An XQuery version number consists of two integers, referred to as the major version number and the minor version number.
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 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 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 is used as the type annotation of an element node that has not been validated, or has been validated in skip mode.
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 is derived by restriction from xs:duration. The lexical representation of xs:yearMonthDuration is restricted to contain only year and month components.
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.