Screaming Penguin - Source Does Matter

devShed has a quite comprehensive intro tutorial for Tomcat, Cocoon, XML and XSLT. This tutorial really only uses Cocoon to perform the XSL transform on XML documents and there are faster ways to do that (speaking from "learned the hard way" experience) but just the same it is a good starting point. Checkit -->.   Cocoon: XML->XSLT->HTML