The XPath standard

Version 1.0 of the XML Path Language (XPath) was developed by W³C and released as a recommendation on 16 November 1999. This standard can be found at 'http://www.w3.org/TR/xpath'.

Some parts of this standard form discrete subsets that are referenced from XSLT and other standards. XSLT makes much use of patterns (which are in fact defined in the XSLT standard). A pattern is a restricted form of location path, which in turn is just part of the full expression language.