easiest way is to use Rick Jelliffe's schematron which is an xsl
stylesheet that writes xsl stylesheets that check xml files:

http://www.ascc.net/xml/resource/schematron/schematron.html

I could send you one of mine, a hand hand written one rather than
a schematron schema, but perhaps you are not interested in checking
OpenMath Content Dictionaries.

David


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list