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Re: a question regarding to semantics of rdfs:subClassOf

From: Jos de Bruijn <jos.debruijn@deri.org>
Date: Wed, 12 Oct 2005 10:46:20 +0200
To: Alan Wu <alan.wu@oracle.com>
Cc: semantic-web at W3C <semantic-web@w3c.org>, public-webont-comments@w3.org
Message-Id: <1129106780.9059.19.camel@localhost.localdomain>
Hi Alan, all,

> Can someone please clarify this for me.
> In Section 3.2.1 of OWL Web Ontology Lang Ref, it mentioned that
>         The rdfs:subClassOf construct is defined as part of RDF
>         Schema. Its 
>         meaning in OWL is *exactly the same* .....
> However, RDFS semantic conditions table in Section 4.1 of RDF
> Semantics 
> defines rdfs:subClassOf to be an "if ... then ... " relationship,
> whereas the If-and-only-if conditions table in Section 5.2 of OWL
> Semantics 
> and Abstract Syntax defines rdfs:subClassOf to be "iff" 
> >From the definition, it seems that OWL defines subclass relationship
> stronger than RDFS does. My intuitive understanding (please correct me
> if I am wrong)
> is that, in OWL, if the class extension of c1 is a subset of class
> extension
> of c2, then c1 is subClassOf c2.

You are completely right. The subclass relationship in OWL is indeed
stronger than the subclass relationship in RDFS. I guess this is a
mistake in the OWL Reference document (I'm CCing public-webont-comments,
hoping this mistake will be rectified in the errata).

The authors of the OWL reference document may have been misled by the
informative section 4.2 of the RDF semantics document [1] which
describes a possible extension of the RDFS semantics to include the
if-and-only-if definitions which are in OWL.

Best, Jos

[1] http://www.w3.org/TR/rdf-mt/

> I am not trying to be picky about the wording here. Just try to
> understand
> this better.
> Thanks,
> Zhe (Alan) Wu
> Oracle
Jos de Bruijn, http://www.uibk.ac.at/~c703239/
+43 512 507 6475         jos.debruijn@deri.org

DERI                      http://www.deri.org/
An expert is a person who has made all the 
mistakes that can be made in a very narrow 
  - Niels Bohr

Received on Wednesday, 12 October 2005 08:47:31 UTC

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