A site description may be as simple as a brief text description. Alternately, you may specify a URL pointing to an HTML file. The URL can be specified as absolute of relative. If relative, the URL is assumed to be relative to site.xml.
An update site may point to the URL of a file listing update site mirror definitions. This URL can be absolute or relative to this site.
The updates mirror file (the one specified in the Site Mirrors section above) contains a list of mirror locations. Its format is defined by the following dtd:
<!ELEMENT mirrors (mirror*))>
<!ELEMENT mirror EMPTY>
url CDATA #REQUIRED
label CDATA #REQUIRED