Where does RDF fit in with XQuery?

Hi,

I'm struggling a bit with understanding the role of RDF and its relationship
to XML Schema and now XQuery.  Any help anyone can offer to clarify things a
bit is much appreciated.

What role (if any) does RDF play with respect to XQuery?  XQuery allows me
to query across multiple XML documents.  If those documents are described
using RDF does that help me formulate my queries in any way?  For example,
RDF can inform me of the relationships between different XML documents.  Or
is the XML Schema for those documents more relevant?  Or are they both
relevant?

Thanks,

Gary