Re: a question regarding to semantics of rdfs:subClassOf

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

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