Stylesheets can format the same page in several different styles. One view can be a fancy formatted HTML page. Another can be a plain printable page. A third might be a WAP view. Or you may have multiple styles for different sections in a site.
The same XML source of this page is used to produce two different views:
The dispatch servlet for *.xml files looks for a ?plain query string. The servlet sets the caucho.xsl.stylesheet attribute to plain.xsl or default.xsl and forwards the page to the XTP servlet. The ?plain query uses plain.xsl. Anything else uses default.xsl.