Identification of RDFa content

This may have been discussed before, in which case apologies. I have not
seen a reference to it in the latest draft.

The question: how does one discover that an XHTML file is 'RDFa-d'? The
issue stroke me as a result of some discussions lately around the
Tabulator[1] and Chris Bizer's announcement[2]. In both cases one can
see engines that are able to make an indirect step, so to say; ie, they
get a URI to a traditional site, but they can deduce the presence of a
corresponding RDF data which they can add to their graph they build and
explore. Examples are the <link references to RDF data, or the GRDDL
profile.

Hence the question again: how does an automatic procedure 'know' that an
XHTML file contains RDFa encoded extra RDF data? Of course, a processor
could RDFa process *all* XHTML file it gets hold of, but it may be worth
adding some standard notification. Also, if such identification was
around, the same URI could be used both for human consumption and for an
RDFa-aware RDF environment.

One would think of a profile attribute or is some sort of a special and
predefined <link>... whichever. Something would be good.

Any thoughts?

Ivan


[1] http://dig.csail.mit.edu/breadcrumbs/node/165
[2] http://lists.w3.org/Archives/Public/semantic-web/2006Oct/0065.html

-- 

Ivan Herman, W3C Semantic Web Activity Lead
URL: http://www.w3.org/People/Ivan/
PGP Key: http://www.cwi.nl/%7Eivan/AboutMe/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf