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Re: raised in comment: owl:class still needed? Does this effect Test LC?

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 22 May 2003 08:23:51 -0400 (EDT)
Message-Id: <20030522.082351.125111317.pfps@research.bell-labs.com>
To: hendler@cs.umd.edu
Cc: www-webont-wg@w3.org

From: Jim Hendler <hendler@cs.umd.edu>
Subject: raised in comment: owl:class still needed? Does this effect Test LC?
Date: Wed, 14 May 2003 11:19:38 -0400

> 
> One part of one of our public comments from RDF Core asks:
> 
> RDFCore: Comments on OWL Reference
> http://lists.w3.org/Archives/Public/public-webont-comments/2003May/0004.html
> 
>    #owlref-rdfcore-owl-class-denotation
>    It has been suggested to
>    RDFCore that owl:Class is not needed.  RDFCore requests the
>    creation of test cases to clearly illustrate the differences
>    between owl:Class and rdfs:Class.
> 
> I'd like to see such a test (or tests) in our LC Test document, as it 
> is likely that we will get this same or similar comment again.  If 
> such a test cannot be generated, then I believe we need to reopen 
> issue 5.20 as it was determined at the Bristol f2f:
> 
>   re 5.20 Should OWL provide synonyms for RDF and RDFS objects? no, 
> owl should not have synonyms; owl:Class is not a synonym.
> 
> (this is part of a long thread and the resolution included this and 
> other statements, but I believe the above is where the WG officially 
> agreed owl:class was not a synonym)
> 
> and appropriately change our documents.
> 
> Peter/Ian (or anyone else) - can one of you remind the WG the 
> difference and design a test case for it?

[copied out of another message]

The RDFS-compatible semantics for OWL DL heavily depends on owl:Class (more
precisely, on IOC, the class extension of owl:Class).  If the distinction
between owl:Class and rdfs:Class was removed the semantics would be quite
different.

Test cases are rather hard to come by, as OWL DL is designed so as to
prevent one from interacting with classes that are not OWL classes.

However, if one looks at RDF graphs that are not in OWL DL one can see the
difference.  For example,

ex:a rdf:type rdfs:Class .
ex:ia rdf:type ex:a .

currently does not OWL DL entail

ex:ia rdf:type _:i .
_:i owl:intersectionOf _:l1 .
_:l1 rdf:type rdf:List .
_:l1 rdf:first ex:a .
_:l1 rdf:rest rdf:nil .

but it would if owl:Class was replaced with rdfs:Class in the semantics.

peter
Received on Thursday, 22 May 2003 08:24:08 GMT

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