XPath 3

XPath 3 is the latest version of the

XPath 1.0 and XPath 2.0

XPath 3.0 became a

New features in XPath 3.0

Compared to XPath 2.0, XPath 3.0 adds the following new features:

Inline function expressions: Anonymous functions can be created in an expression context. For example, the expression function($a as xs:double, $b as xs:double) as xs:double { $a * $b } creates a function that returns the product of its two arguments. The expression collection()/(let $a := . return function() { $a }) creates a sequence of functions, each one returning a different node from a collection.
Dynamic function calls: Function values may be called without being referenced by name. For example, $f[2]("Hi there") fetches the second item from sequence $f, and invokes it as a function, passing the string "Hi there" as argument.
Union types: Union types, as defined in XML Schema, may be used in type conversions and function type signatures.
Namespace literals: URI literals
. For example, the qualified name math:pi may be expanded to Q{http://www.w3.org/2005/xpath-functions/math}pi, embedding the namespace URI inside the prefix.
String concatenation operator: The new ||
string concatenation
: $a || $b is equivalent to fn:concat($a, $b).
Mapping operator: The new ! operator performs simple mapping: E1 ! E2 evaluates E2 for each item in the sequence E1, and concatenates the resulting items. This is comparable to the path operator /, but the ! operator does not perform duplicate elimination nor document ordering of the results.

XPath 3.1 mainly adds support for

array and map (associative array) data types. These types and their associated functionality are intended to ease working with JSON

Another innovation is the arrow operator => for function chaining. For example, the XPath 2.0 expression

contains(upper-case(substring-before($in, ' ')), 'X')

can now be written

$in => substring-before(' ') => upper-case() => contains('X')

This computing article is a stub. You can help Wikipedia by expanding it.