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

From: Jos De_Roo <jos.deroo@agfa.com>
Date: Sun, 25 May 2003 01:27:51 +0200
To: pfps@research.bell-labs.com
Cc: hendler@cs.umd.edu, www-webont-wg@w3.org, www-webont-wg-request@w3.org
Message-ID: <OF5EA1682C.1090F051-ONC1256D30.00808611-C1256D30.0080E5B4@agfa.be>


Peter F. Patel-Schneider wrote:
> From: "Jos De_Roo" <jos.deroo@agfa.com>
> Subject: Re: raised in comment: owl:class still needed? Does this effect
Test LC?
> Date: Sat, 24 May 2003 23:09:49 +0200
>
> >
> > Last Thursday Jim Hendler wrote:
> > >At 8:23 AM -0400 5/22/03, Peter F. Patel-Schneider wrote:
> > >>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
> > >
> > >Looks good.
> >
> > I was thinking that too, but the comment was
> >
> > >>>     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.
> >
> > and although that test case illustrates the differences
> > it is not showing that owl:Class is needed.
>
> Well, in a certain sense none of owl:Class, owl:DatatypeProperty,
> owl:ObjectProperty, and probably quite a few other bits of OWL vocabulary
> are not *needed*.  However, it is *desirable* to have them around.

Could there be a class that is an rdfs:Class but not an owl:Class?
If so, is there an example of such a class?
(not talking about illegal OWL Lite or OWL DL documents)

> > >             What about another one that somehow reflects that
> > >rdfs:class is a member of rdfs:class, but owl:class is not a member
> > >of owl:class?
> >
> > Maybe owl:Class rdf:type owl:Class is not a legal DL document
> > just as rdfs:Class rdf:type rdfs:Class isn't, but that doesn't
> > mean that it's not legal OWL (and a true statement); again it
> > is not showing that owl:Class is needed.
> >
> > --
> > Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
>
> peter

--
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Saturday, 24 May 2003 19:28:20 GMT

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