DOCBOOK-APPS: XSL-Style: bibliosource

Good Morning list,
(In case somebody wondered: yes, today is my bibliography day .-)

How should I reference webpages in my bibliography?
I curently do it like this:
 <biblioentry>
  <abbrev>bibSunXML</abbrev>
  <biblioset relation='webl'>
    <title>The Java API for Xml Processing (JAXP) Tutorial</title>
    <bibliosource id="linkSunXML">
       <ulink
url="http://java.sun.com/xml/jaxp/dist/1.1/docs/tutorial/index.html">
       http://java.sun.com/xml/jaxp/dist/1.1/docs/tutorial/index.html
</ulink>  
    </bibliosource>
  </biblioset>
 </biblioentry>

The bibliosource, however, is unknown to both the PDF and the HTML
style. Could this be included in the styles, please? Or should I use
something else, like <ulink>?

Stephan Wiesner