XML.com have a good article on profiling the XML schema by Paul Kiel. The article is very well explained and analyse in depth the XML schema, there is lot of data used in the analys and maybe its more than needed. There is also an excellent research paper on Analysis of XML schema usage which was presented at the XML 2005 conference that you might check it out.

XML Schema is now 5 years old, having matured from a newborn into an active youngster. So what have we learned about this young one's personality? We've always known it was complex. Indeed, the original debate about whether to make it a Recommendation indicated concern. This rich toolset has caused schema designers to wonder which features they should or should not use. If we analyze what people are actually implementing, perhaps we can glean some guidance. I decided to embark on a quest to see if we can put together a profile of XML Schema based on experiences thus far.