Why is this there no means to link to an external rdf file?

Why is this there no means to link to an external rdf file?

Jonathan Chetwynd
Accessibility Consultant on Media Literacy and the Internet

it would seem to be useful from a maintenance and bandwidth issue,  
and pragmatic regarding current validators:
timbl suggested on irc: ask the validator  people to make a validator  
which does not treat that (embedded RDF) as an error.

xhtml provides <link rel="meta" type="application/rdf+xml"  
href="metadata.rdf"/>
<?xml-stylesheet...> links to an external stylesheet