W3C home > Mailing lists > Public > public-sw-meaning@w3.org > March 2004

Media types for the Semantic Web

From: Mark Baker <distobj@acm.org>
Date: Wed, 31 Mar 2004 12:13:19 -0500
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: public-sw-meaning@w3.org
Message-ID: <20040331171319.GR11976@markbaker.ca>

BTW, is this on topic for this list?  I can't tell any more. 8-/

On Fri, Mar 26, 2004 at 01:28:02PM -0500, Peter F. Patel-Schneider wrote:
> An OWL ontology is much, much more than an RDF graph, unless you believe in
> the strongest of the various one-meaning proposals that have been bandied
> about.
> 
> For example, if I ask you whether the RDF graph
> 
> 	ex:foo owl:sameAs ex:bar .
> 
> entails
> 
> 	ex:foo rdfs:subClassOf ex:bar .
> 
> you *should* say no, because I have only licensed you to treat this graph
> as an RDF graph, not an OWL ontology.

Sounds reasonable.  I like the use of the term "licensed" there too, as
it jives with my view of the role of media types.

I'm still a novice on "model theory" stuff, so please help me understand
where I might be wrong, but here's how I currently see the different
meanings that one might have when transferring a graph;

1.  I'm communicating just this graph
2.  I'm communicating this graph and some axiomatic triples
3.  I'm communicating this graph and every inferred triple
4.  I'm communicating this graph, these axiomatic triples, and all
inferred triples from the resulting merged graph

I believe that using application/rdf+xml handles #1 easily, and #2
when the axiomatic triples are the RDF axiomatic triples (since those
are equivalent in that case, it seems).  When the axiomatic triples are
not (just) RDF's, then a new media type seems necessary.  FWIW, what I
believe this suggests is that axiomatic triples should be avoided where
possible, precisely because they lead to an explosion of media types
(or an explosion of non-self-descriptive messages if new media types
aren't minted 8-).  This seemed to be Dan's concern;

""
Now further up the spectrum, we might consider application/owl+xml.

I find that objectionable because it suggests that
dublin core and adobe XMP and RSS and so on
need their own media types, and it leaves me
wondering what media type to use if for
a document that mixes all these vocabularies
together.
""
  -- http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0162.html

AFAIK though, RSS and XMP don't have their own axiomatic triples, nor
require inferencing, so Dan's argument seems to be a strawman;
application/rdf+xml should suffice for them.

For #3 and #4, I think new media types are also required.

Thoughts?

Mark.
-- 
Mark Baker.   Ottawa, Ontario, CANADA.        http://www.markbaker.ca
Received on Wednesday, 31 March 2004 12:07:40 GMT

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