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Re: MISC: Internet Media Type registration: proposed TAG finding

From: Dan Connolly <connolly@w3.org>
Date: 22 May 2002 15:29:53 -0500
To: "Peter F. "Patel-Schneider <pfps@research.bell-labs.com>
Cc: WebOnt WG <www-webont-wg@w3.org>
Message-Id: <1022099394.14014.92.camel@dirk>
On Wed, 2002-05-22 at 06:17, Peter F. Patel-Schneider wrote:
> The W3C TAG has come up with a proposed finding about internet media type
> registration, which will affect WebOnt sooner or later.  Also, a message
> about the finding was sent to the RDF Core (but not to WebOnt), and there
> already is discussion in RDF Core as to how to handle media types for RDF
> and other Semantic Web languages.
> [The initial message states ``RDF (RDFCore, RDFS, WebOnt, ...)''.  I find
> it rather disconcerting to see words to the effect that WebOnt is (just)
> making another dialect of RDF, no different in status from RDFS.

Why do you find it disconcerting? That's exactly what WebOnt is,
until we decide otherwise...

"A DAML+OIL knowledge base is a collection of RDF triples. DAML+OIL
prescribes a specific meaning for triples that use the DAML+OIL
vocabulary. This document informally specifies which collections of RDF
triples constitute the DAML+OIL vocabulary and what the prescribed
meaning of such triples is."

 -- http://www.w3.org/TR/2001/NOTE-daml+oil-reference-20011218

>  I ask
> that the WebOnt WG discuss whether to send a polite note back rejecting
> this interpretation of our work.

I don't think we should.

> ]
> I propose that we let this issue affect us sooner, as I believe that there
> is a correct way and an incorrect way to handle the issue.  Moreover, these
> two views differ on how RDFS is treated.
> I believe that the incorrect way to handle the issue of media types for RDF
> and other Semantic Web languages is to have one media type for all
> RDF-derived languages.  Thus RDF/XML (RDF written in XML), RDFS/XML (RDFS
> written in XML), and OWL/RDF/XML (OWL written in RDF written in XML) would
> all have the same media type, and applications would have to determine
> which kind of processing to perform by the content of the documents.

It seems to me that applications determine which kind of processing
to perform independent of document contents and media types.

The media type says what the document means; there may be lots
of ways to process it.

> I believe that the correct way to handle the issue of media types for RDF
> and other Semantic Web languages is to have a different media type for each
> Semantic Web language that requires different processing.  By ``different
> processing'' I mean that either there are some different semantic
> conditions for the language, or there are some extra syntactic constructs
> in the language.

That doesn't make any sense, to me. There are different semantics
for RSS, dublin core, prism, and all the other RDF vocabularies.
The point of RDF is being able to mix them all into the same
document; what media type would you suggest for a document
that uses a variety of vocabularies?

One of the documents I work on quite a bit starts thus...


>  Thus even if OWL could be written completely in RDF/XML
> (which would require an official dark triples solution from RDF Core),

(I don't think so)

> there would be a different media type for OWL because a processor for OWL
> would have to take into account the extra semantics for OWL constructions.

A consumer of the above document either or does or doesn't grok
DAML+OIL semantics; it can come to more of the relevant conclusions
if it applies DAML+OIL axioms, but since everything is monotonic,
there's no harm done if it doesn't apply those axioms.

This is the principle of partial understanding in action.
I have tried to make this point in the past...
but I'm not having much luck.

> This view of media types for RDF and other Semantic Web languages has the
> corrollory that RDFS has a different media type from RDF.  Why?  Because
> RDFS has extra semantic conditions in its model theory.  
> Questions:  Should this be a WebOnt issue?  Probably, so .....
> TITLE:	Internet Media Type for OWL
> DESCRIPTION: The W3C TAG has just issued a proposed finding about internet
> 	     media types.  WebOnt will almost certainly have to identify,
> 	     and perhaps register, an internet media type for OWL
> 	     documents.  RDF Core will almost certainly also identify an
> 	     internet media type for RDF.  WebOnt will have to coordinate
> 	     with RDF Core on the relationship between the media types.
> RAISED BY:   Peter F. Patel-Schneider
> REFERENCE:   http:///lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002May/0072.html
> Peter F. Patel-Schneider
> Bell Labs Research
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Wednesday, 22 May 2002 16:29:52 UTC

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