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RE: SEM: Light review of semantics document

From: Massimo Marchiori <massimo@w3.org>
Date: Mon, 11 Nov 2002 00:44:29 +0100
To: "<Www-Webont-Wg" <www-webont-wg@w3.org>
Message-ID: <NGBBJNKIMLOPPCFHEJEMMEPODAAA.massimo@w3.org>

Quick summary: I agree wholeheartedly with Pat [1] (I could have written the precise same things, but for sure without Pat's style
effectiveness ;).
Now, secondarily: Chris [2] and Jonathan [3], to which emails I also fully agree with, recall the other important point in action
here, "context" or "comments", that are different sides of the same coin.
Note, to close the loop, this ties with the versioning issue as well, cf [4] and later emails, and the mismatch between the original
DAML+OIL "ontology" concept, and the different environment of the current OWL-RDF representations (exactly the point that, under
different aspects, has resurfaced here).
Point to remember from that versioning/import discussion:
a) you don't have necessarily to follow the same definition of ontology that DAML+OIL had (and, this is the point that has really
resurfaced here): we now live in the RDF graph.
b) in order to provide more context/structure info, transparent annotations could be added (cf. [5]); although, note from that
email, this could clash with the logical import.

-M


[1] http://lists.w3.org/Archives/Public/www-webont-wg/2002Nov/0113.html
[2] http://lists.w3.org/Archives/Public/www-webont-wg/2002Nov/0118.html
[3] http://lists.w3.org/Archives/Public/www-webont-wg/2002Nov/0125.html
[4] http://lists.w3.org/Archives/Public/www-webont-wg/2002Sep/0430.html
[5] http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0060.html


> -----Original Message-----
> From: www-webont-wg-request@w3.org
> [mailto:www-webont-wg-request@w3.org]On Behalf Of Jonathan Borden
> Sent: Sunday, November 10, 2002 5:01 PM
> To: Christopher Welty; www-webont-wg@w3.org; Jim Hendler
> Subject: Re: SEM: Light review of semantics document
>
>
>
> Jim Hendler wrote:
> >
> > At 3:00 PM -0500 11/8/02, Christopher Welty wrote:
> > >I have to agree with Pat here, guys.  The meaning of an "owl:ontology"
> tag
> > >inside an RDF document is simply that the document contains OWL syntax,
> > >not some hard to pin down notion of a separation between definitions and
> > >data.
> > >
> >
> > Chris/Pat - I think you guys misunderstood me - I believe that all of
> > these things are OWL documents, but I'm concerned with a small matter
> > of usage.  The way I see it, there are documents which are clearly
> > owl ontologies because they define terms and properties and the like.
> > There are also owl documents that only use those terms and, in fact,
> > there is no reason that there will be any trace of any OWL vocabulary
> > in those documents.  For example, if Chris defines an ontology about
> > people, I could have a document which contains only the following:
>
>
> I agree. Especially if you consider OWL (full) as an extension of RDFS, you
> are going to find a whole host of problems trying to draw a sharp line in
> the sand between RDF data and OWL ontologies.
>
> Indeed once an OWL 'document' with an owl:Ontology triple has been parsed
> into a triple store, the connection between the owl:Ontology triple and the
> rest of the triples has been effectively lost -- I', and others, have
> suggested that RDF needs some notion of 'context' to fix this but that is
> the simple fact of RDF. You pick your cake, now eat it.
>
>
> >
> > Namespace definitions to RDF and to Chris' document
> >
> > <rdf:RDF>
> >    <chris:person rdf:id="Hendler" />
> > </rdf:RDF>
>
> Well what if *I* say something like:
>
> chris:person owl:subClassOf owl:Class .
>
> elsewhere, and suppose I believe this :-), now your supposedly perfect RDF
> document *does* use OWL terms...
>
>
> >
> > by the definition "uses owl terminology" this is NOT and owl
> > document.  By the definition "uses terms from an owl ontology" this
> > is an Owl document.
> >
> > So I am asking for terminology that would
> >     i. let me differentiate this document from an arbitrary RDF
> > document (and Pat, please note I wasn't being anti-logical, but it
> > seems to me we don't need this distinction to have a logical meaning
> > in the formal sense -- I'm simply looking for a common term to mean
> > RDF documents that are expecting to be linked to owl ontologies) --
> > Jeff called this a data document, which Pat didn't like.
>
> Given OWL Full and the spirit of RDF, where anyone *might* say anything
> about anything at anytime, you just cannot draw a sharp line between the
> two. At most you can say that it is unknown if an RDF 'document' is an OWL
> 'document'
>
> >    ii. lets me differentiate this kind of document from an owl
> > document which does contain class and property definitions and
> > restrictions.  I DO KNOW what to call the ones that have that (an
> > ontology), but not what to call the other ones.
> >
> >   I believe strongly that this is not a critical issue of language
> > design, it's simply a suggestion we develop consistent terms so we
> > get our message out.
> > Technically, it is clear to me the document above is an RDF document
> > - it would use the RDF Model Theory and all would be happy.  But
> > colloquially, we need to be able to discuss these documents with a
> > term that people in the outside world can understand.
> >
> >   In class, I refer to these as "Owl data sets" and the students get
> > it, I'd be happy with that term.
> >
> > So, I ask Pat/Chris and anyone else inclined to help out:
> >
> >   what name shall we use for documents that are in the class with the
> > following properties:
> >
> > Document a rdf:RDF document AND
> > Document uses terms from a owl ontology document AND
> > Document NOT a owl ontology document.
> >
> > IMHO, If we call such a document an "ontology," we're going to
> > confuse  a lot of people.
>
> This motivates me to write up the media-type document:
>
> The publisher of a document can label one as
> application/rdf+xml
>
> and another as
> application/owl+xml
>
> by definition, *any* RDF document labelled as application/owl+xml is part of
> an ontology.
> by definition *any* RDF document labelled as application/rdf+xml is RDF and
> *might be* part of an ontology
>
> Good luck folks, but this is an artifact of RDF and OWL Full. Of course I am
> willing to listen to a good argument to the contrary its just that I can't
> imagine some plain ol' RDF being 'converted' into OWL at some later time, or
> on discovery of some other document e.g. suppose:
>
> http://example.org/RDF/data.rdf
> <rdf:RDF>
>     <foo:bar rdf:ID="baz"/>
> </rdf:RDF>
>
> and then
>
> http://example.org/OWL/ontology-decls:
> <rdf:RDF>
>     <owl:Ontology rdf:about="http://example.org/RDF/data.rdf">
>         ...
>     </owl:Ontology>
>     <owl:Class rdf:about="http://example.org/RDF/data.rdf#baz">
>         <owl:subClassOf rdf:resource="...#bop"/>
>     </owl:Class>
> </rdf:RDF>
>
> Jonathan
>
Received on Sunday, 10 November 2002 18:45:18 GMT

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