Apache Xalan

Apache Xalan is a popular open-source XSLT processing component developed by the Apache XML Foundation. Stylus Studio XSLT tools provide seamless integration with the Xalan XSLT Processor, enabling you to execute, debug, and optimize your XSLT stylesheets using the Xalan XSLT processor. No additional downloads are necessary — the latest version of Apache Xalan-J is bundled. This tutorial provides an overview of how to use the many features and functions in Stylus Studio that are geared towards accelerating development of Xalan applications including how to transform XML using XSLT stylesheets and Xalan.

http://www.stylusstudio.com/xslt/xalan.html