How should a crawler or UA interpret an XMDP profile referenced in a document?
• Very similar to DTDs. A crawler or UA may interpret an XMDP profile URL simply as an idenitifier for which it knows is a well-defined microformat vocabulary. It may also go read that profile URL, and parse it as XMDP, and thus mechanically know which class values are defined, which new rel/rev values have been introduced, and which properties and values have been defined.