XSL TRANSFORMATIONS (XSLT) VERSION 3.0
From the post:
The XSLT Working Group has published today a Last Call Working Draft of XSL Transformations (XSLT) Version 3.0. This specification defines the syntax and semantics of XSLT 3.0, a language for transforming XML documents into other XML documents. A transformation in the XSLT language is expressed in the form of a stylesheet, whose syntax is well-formed XML. Comments are welcome by 10 February 2014. Learn more about the Extensible Markup Language (XML) Activity.
One of the successful activities at the W3C.
A fundamental part of your XML toolkit.