The proxy portlet reads data and then applies an XSLT transformation before the result is returned to the client web browser. XSLT is a standard for how to transform XML. There is plenty of material available concerning the subject on the web.
Below you find some recommended links to ease the development of XSLT transformations.
- XSLT standard
- XPath standard (used for expressions in XSLT)
- XSLT Introduction (w3school)
- XPath tutorial (w3school)
Tools you might find useful when developing with the proxy portlet.
- Firebug extension for Firefox-web browser.