XPath 3 is the latest version of the

XML Path Language XPath (XML Path Language) is an expression language designed to support the query or transformation of XML documents. It was defined by the World Wide Web Consortium (W3C) and can be used to compute values (e.g., strings, numbers, or Boolean v ...

, a

query language Query languages, data query languages or database query languages (DQL) are computer languages used to make queries in databases and information systems. A well known example is the Structured Query Language (SQL). Types Broadly, query language ...

for selecting nodes in

XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. T ...

documents. It supersedes

XPath 1.0 XPath (XML Path Language) is an expression language designed to support the query or transformation of XML documents. It was defined by the World Wide Web Consortium (W3C) and can be used to compute values (e.g., strings, numbers, or Boolean v ...

and

XPath 2.0 XPath 2.0 is a version of the XPath language defined by the World Wide Web Consortium, W3C. It became a recommendation on 23 January 2007. As a W3C Recommendation it was superseded by XPath 3.0 on 10 April 2014. XPath is used primarily for selec ...

. XPath 3.0 became a

W3C Recommendation The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 and led by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working to ...

on 8 April 2014, while XPath 3.1 became a

on 21 March 2017.

New features in XPath 3.0

Compared to

, XPath 3.0 adds the following new features: ; Inline function expressions :

Anonymous function In computer programming, an anonymous function (function literal, lambda abstraction, lambda function, lambda expression or block) is a function definition that is not bound to an identifier. Anonymous functions are often arguments being passed to ...

s can be created in an

expression Expression may refer to: Linguistics * Expression (linguistics), a word, phrase, or sentence * Fixed expression, a form of words with a specific meaning * Idiom, a type of fixed expression * Metaphorical expression, a particular word, phrase, o ...

context. For example, the expression creates a function that returns the product of its two arguments. The expression 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, fetches the second item from sequence $f, and invokes it as a function, passing the string "Hi there" as argument. ; Union types :

Union type In computer science, a union is a value that may have any of several representations or formats within the same position in memory; that consists of a variable that may hold such a data structure. Some programming languages support special data t ...

s, as defined in

XML Schema An XML schema is a description of a type of Extensible Markup Language, XML document, typically expressed in terms of constraints on the structure and content of documents of that type, above and beyond the basic syntactical constraints imposed ...

, may be used in

type conversion In computer science, type conversion, type casting, type coercion, and type juggling are different ways of changing an expression from one data type to another. An example would be the conversion of an integer value into a floating point value ...

s and function

type signature In computer science, a type signature or type annotation defines the inputs and outputs for a function, subroutine or method. A type signature includes the number, types, and order of the arguments contained by a function. A type signature is typ ...

s. ; Namespace literals :

XML namespace XML namespaces are used for providing uniquely named elements and attributes in an XML document. They are defined in a W3C recommendation. An XML instance may contain element or attribute names from more than one XML vocabulary. If each vocabulary ...

s may be referenced using braced

URI Uri may refer to: Places * Canton of Uri, a canton in Switzerland * Úri, a village and commune in Hungary * Uri, Iran, a village in East Azerbaijan Province * Uri, Jammu and Kashmir, a town in India * Uri (island), an island off Malakula Islan ...

literals. For example, the qualified name math:pi may be expanded to , embedding the namespace URI inside the prefix. ; String concatenation operator : The new , , operator may be used for

string concatenation In formal language theory and computer programming, string concatenation is the operation of joining character strings end-to-end. For example, the concatenation of "snow" and "ball" is "snowball". In certain formalisations of concatenat ...

: $a , , $b is equivalent to . ; 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.

New features in XPath 3.1

XPath 3.1 mainly adds support for

array An array is a systematic arrangement of similar objects, usually in rows and columns. Things called an array include: {{TOC right Music * In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...

and map (

associative array In computer science, an associative array, map, symbol table, or dictionary is an abstract data type that stores a collection of (key, value) pairs, such that each possible key appears at most once in the collection. In mathematical terms an as ...

) data types. These types and their associated functionality are intended to ease working with

JSON JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other ser ...

data. Another innovation is the arrow operator => for function chaining. For example, the XPath 2.0 expression : can now be written :

References

* * XML data access {{computing-stub