Just as an experiment (because I'm trying to figure out how to better
rationalize my own metadata), and FWIW, I thought I'd see what it
would take to make this MADS example ...

http://www.loc.gov/standards/mads/mads-subject.xml

... valid RDF:  Here it is:

<mads:Topic xmlns:mads="http://www.loc.gov/mads/" 
   xml:base="http://www.loc.gov/lcsh/" 
   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 
   rdf:about="lcsh:Computer_Programming">
   <mads:name>Computer programming</mads:name>
   <mads:broader rdf:resource="Computers"/>
   <mads:narrower rdf:resource="Programming_Languages"/>
<!-- the below relation is pretty meaningless of course -->
   <mads:otherRelation rdf:resource="Systems_Analysis"/>
</mads:Topic>

Am not sure the details are quite right, but it's less verbose than
the pure xml version, and almost everything is now a uri resource. 
Because it relies more on elements, it's also more easy-to-handle xml
(an old mantra of mine).  And, of course, that doesn't include
whatever else might come along with RDF.

Bruce