W3C home > Mailing lists > Public > www-webont-wg@w3.org > November 2002

Re: SEM: Light review of semantics document

From: pat hayes <phayes@ai.uwf.edu>
Date: Sun, 10 Nov 2002 22:20:49 -0600
Message-Id: <p05111b15b9f4debb122c@[10.0.100.86]>
To: "Jonathan Borden" <jonathan@openhealth.org>
Cc: <www-webont-wg@w3.org>

>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?

>
>     <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.

Pat


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Received on Sunday, 10 November 2002 23:20:22 GMT

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