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Re: SEM: Light review of semantics document

From: Jonathan Borden <jonathan@openhealth.org>
Date: Sun, 10 Nov 2002 23:12:14 -0500
Message-ID: <012601c28938$84aefe70$7c674544@ne.mediaone.net>
To: "pat hayes" <phayes@ai.uwf.edu>
Cc: <www-webont-wg@w3.org>

pat hayes wrote:

> >pat hayes wrote:
> >>
> >>  I have no problem with that, but I have always understood this to
> >>  simply be an XML marker for the presence of OWL syntax in the RDF
> >>  graph. Why do we need to say anything more than that? "owl:ontology"
> >>  isn't in the graph, right? So its not in the namespace, and it has no
> >>  semantics. If "owl:ontology" is in the OWL namespace, then we ought
> >>  to say what an RDF triple which includes that name means.
> >
> >I missed that. I had thought that once we decided that OWL was using RDF
> >syntax that <owl:Ontology rdf:about="foo"> was intended to be an RDF
> >typedNode. That is to say generate at least the following triple:
> >
> >:foo rdf:type owl:Ontology .
>
> Well, OK, I can go with that. BUt then there is a serious gap in the
> OWL semantics, which doesn't mention owl:Ontology anywhere. I gather
> from the above that whatever it is, it must have an RDFS class
> extension. Is there anything more to be said about what it means? If
> so, we ought to say it quickly.
>
> >...
> >>
> >>  The difference is that one of them contains OWL syntax and the other
> >>  does not. End of story.
> >
> >That's the problem, since in OWL Full, as in RDF, we might subClassOf and
> >subPropertyOf essentially _anything_ then it is indeed possible to write
> >something that is intended to be an ontology (whatever that may be, let's
> >use the English definition) that doesn't use any actual terms from the
OWL
> >namespace.
>
> Presumably, in this case, OWL won't know what it means so won't draw
> any conclusions from it. ( I have this weird feeling that we are
> talking about an Alice-in-wonderland scenario, however.)
>
> >Suppose
> >
> >ex:myClass rdfs:subClassOf owl:Class .
> >ex:myOnt rdfs:subClassOf owl:Ontology .
> >
> >and then an 'instance' document
> >
> ><rdf:RDF>
> >     <ex:myOntology rdf:about="">
> >     </ex:myOntology>
>
> ?? What triple did *that* generate?

<> rdf:type ex:myOntology .

assuming the baseURI is http://example.org/ontology ,

<http://example.org/ontology> rdf:type ex:myOntology .

>
> >
> >     <ex:myClass rdf:ID="foo">
> >         <rdfs:subClassOf rdf:resource="...#yourFoo"/>
> >     </ex:myClass>
> ></rdf:RDF>
> >
> >>  What about the many other cases, such as  <rdf:RDF>....</rdf:RDF>
> >>  which contains non-ground RDFS, say? ...
> >
> >Aren't we agreeing?
>
> I'm not sure: I don't really know what you are saying.
>
> My point here was to object to Jim's characterization of the
> difference in terms of RDF being ground facts and OWL being 'real
> ontologies', on the grounds that this distinction wasn't binary.
>

That's the essential point, that since 'individuals' may be 'classes' (in
OWL Full), that someone might always come along and declare an individual a
class, so there is no absolute distinction.

Jonathan
Received on Sunday, 10 November 2002 23:31:53 GMT

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