A language for addressing parts of an XML document, selecting nodes (elements, attributes, character data, etc.) by their name, their value, and/or their location relative to specified other nodes in a tree view of the document’s structure. XPath is used within other XML standards, for example XQuery and XSL; indeed, XPath version 3.0, released in 2014, is a subset of XQuery.
http://www.w3.org/TR/xpath-30 The XPath (version 3.0) specification