Not needed by SiteMesh, but helpful for users. Make sure examples always point to a valid URL.
for Intellij IDEA (and probably most IDEs), it provides validation and auto-complete when editing XML doc with a schema. Providing a XSD could help to reduce chance of errors and probably reduce the need for documentation.
i was just editing a sitemesh3.xml, wondering if multiple paths is supported per mapping, e.g.
(i'm not asking this question now. just an example)
if there is a xsd, the question will be answered by the XSD.