This document describes the expressions available in X-Query. The names of the expressions correspond to the language constructs of X-Query. In many cases, these are equivalent to an XPath expression of the same name. However, in a few cases the meaning is different or the expression only exists in X-Query, since its serves a special purpose in the context of a database. A syntax diagram illustrates the definition as it appears in the respective production rule of the X-Query grammar. The description is followed by an XPath compatibility note and one or more examples.

The most basic parts of the X-Query language are not covered; we summarize them here. Digits, numbers, and operators are defined as in the lexical rules of the XPath specification (in Section 3.7). However, X-Query adds to the list of operators the special contains operator ~=, which provides text retrieval capabilities. The list of operator names (OperatorName, defined in XPath, Section 3.7, Rule 33) is extended by adj, after, before, betw, between, near, intersect. All of these additions are described below.

The following table lists the expressions available in X-Query, along with the corresponding XPath expressions. An asterisk (*) after the name of an XPath expression indicates that this expression is implemented differently in X-Query. The link in the XPath column leads you to the expression's production rule in the XPath specification.

X-Query Expression	XPath Expression	Short Description
AbbrevAbsoluteLocPath	AbbreviatedAbsoluteLocationPath	select all nodes satisfying some condition
AbbreviatedAxisSpecifier	AbbreviatedAxisSpecifier	specify either child or attribute axis
AbbreviatedStep	AbbreviatedStep	select context node or its parent node
AbsoluteLocationPath	AbsoluteLocationPath	location path starting at the root node
AdditiveExpr	AdditiveExpr	add or subtract numeric values
AndExpr	AndExpr	check if two or more conditions are all true
Argument	Argument	input to a FunctionCall
AxisName	AxisName *	specify axis by name
AxisSpecifier	AxisSpecifier	specify axis in a location step
BetweenExpr	—	select nodes based on a value range
EqualityExpr	EqualityExpr *	check if two values are equal
Expr	Expr	general X-Query expression
FilterExpr	FilterExpr *	select a subset of nodes satisfying some condition
FunctionCall	FunctionCall	call to a function
LocationPath	LocationPath	select nodes along a path
MultiplicativeExpr	MultiplicativeExpr	perform multiplication, division and modulo operations
NameTest	NameTest	check for name of specified node
NodeTest	NodeTest *	check for type or name of specified node
NodeType	NodeType *	token representing a type of node
OrExpr	OrExpr	check if one of the given conditions is true
PathExpr	PathExpr	select a set of nodes
Predicate	Predicate	select a subset of nodes for which the predicate is true
PredicateExpr	PredicateExpr	expression used in a predicate
PrimaryExpr	PrimaryExpr	expression without operators
ProximityExpr	—	specify adjacent values
RelationalExpr	RelationalExpr	compare two numeric values
RelativeLocationPath	RelativeLocationPath	select nodes relative to the context node
SequenceExpr	—	select nodes based on sibling positioning
SetExpr	UnionExpr *	select union or intersection of node sets
SortByClause	—	sort a node set
SortByCharacteristics	—	determine sorting order
Step	Step	select a subset of nodes on a given axis
UnaryExpr	UnaryExpr	change number sign

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