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XPath 3 is the latest version of the XML Path Language, a query language for selecting nodes in XML documents. It supersedes XPath 1.0 and XPath 2.0.
XPath 3.0 became a W3C Recommendation on 8 April 2014, while XPath 3.1 became a W3C Recommendation on 21 March 2017.
Compared to XPath 2.0, XPath 3.0 adds the following new features:
function($aasxs:double,$basxs:double)asxs:double{$a*$b} creates a function that returns the product of its two arguments. The expression collection()/(let$a:=.returnfunction(){$a}) creates a sequence of functions, each one returning a different node from a collection.$f[2]("Hi there") fetches the second item from sequence $f, and invokes it as a function, passing the string "Hi there" as argument.math:pi may be expanded to Q{http://www.w3.org/2005/xpath-functions/math}pi, embedding the namespace URI inside the prefix.|| operator may be used for string concatenation: $a || $b is equivalent to fn:concat($a,$b).! operator performs simple mapping: E1 ! E2 evaluates E2 for each item in the sequence E1, and concatenates the resulting items. This is comparable to the path operator /, but the ! operator does not perform duplicate elimination nor document ordering of the results.XPath 3.1 mainly adds support for array and map (associative array) data types. These types and their associated functionality are intended to ease working with JSON data.
Another innovation is the arrow operator => for function chaining. For example, the XPath 2.0 expression
contains(upper-case(substring-before($in,' ')),'X')can now be written
$in=>substring-before(' ')=>upper-case()=>contains('X')
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