Michael Kay has contributed what might be considered one of the most robust and versatile XSLT processors with his Saxon product. It has one of the largest sets of built-in extension top-level elements, instruction elements, and functions. It also runs on Java and is regularly updated at the source Web site, http://users.iclway.co.uk/mhkay/saxon.
Saxon includes a servlet that allows it to be invoked directly from a URL entered into a browser. You might think of Saxon as the “programmer's XSLT processor,” due to its extended documentation for adding extensions, event handlers, and so forth (see the api-guide.html file in the Saxon user documentation).
The Saxon XSLT processor is available in two forms, a “complete” Saxon API for Java, ...