XHTML/RDF vocabulary documents: scenario from FOAF namespace

Hi

Here's a scenario in which I mix RDF into an XHTML document. My side project, 
FOAF, has a namespace whose URI is http://xmlns.com/foaf/0.1/ and whose default
representation is an XML document that embeds RDF within an XHTML context. 

I chose to embed the RDF (actually RDFS/OWL markup) in the body of the document,
rather than the head, though I wasn't so bothered by that part of the decision.

What I like about this scenario is that the namespace document includes both human 
and machine readable documentation about the FOAF vocabulary. Currently, I do this 
but it means the document can't be DTD or XML Schema validated. 

Dan