Simplified Docbook Relax NG schema

Hello. 

For a system I am working on right now, I need the simplified docbook Relax NG schema file. Google yield the following page:
http://www.docbook.org/docbook-ng/simple/

Not sure if those files are official. Anyway. Everything is working great except the fact that elements like "warning" and "caution" are not part of those schema file. I am not sure if there are any other elements missing too. Is this intended?

Thank you.
/frank