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Re: Denotation of owl:Class

From: pat hayes <phayes@ai.uwf.edu>
Date: Sat, 26 Apr 2003 16:42:40 -0500
Message-Id: <p0521060fbad0acbdad41@[10.0.100.12]>
To: Jeremy Carroll <jjc@hpl.hp.com>
Cc: w3c-rdfcore-wg@w3.org

>Jeremy:
>>>i.e. globally replace owl:Class by rdfs:Class in OWL S&AS and
>>>everything still works.
>Pat:
>>Except that there would then be entailments that weren't legal in OWL-DL.
>
>I overstated the ease of the replacement, there would be some consequential
>changes needed in the correspondence theorem, for instance.
>
>>>You cannot say owl:Class rdfs:subClassOf rdfs:Class or the opposite in OWL
>>>Lite and OWL DL so the need for this distinction is moot.
>
>>But the point is that OWL-DL  needs a name for its universe that it
>>can use. It can't define it, and probably OWL-Full can't either, in
>>fact.
>
>OWL DL (direct semantics) can quite happily call its universe the universe, or
>the domain of discourse or whatever. owl:Class only appears in the first
>sections of S&AS in the mapping rules. I ask the question, what would have to
>change in the RDFS compatible semantics to accomodate changing the mapping
>rules by replaceing owl:Class with rdfs:Class.

Im not sure what this means. If all you want to preserve is 
OWL-DL/RDF, and if you are willing to stay within the -DL fragment 
and never stray outside it, then you may be right. If you want your 
OWL-DL to also be embedded in OWL-Full, however, you need a name for 
the DL universe.

>
>OWL DL (rdfs compatible semantics) does need a concept corresponding to
>owl:Class (i.e. some subclass of rdfs:Class, not including the builtin
>classes), but it does not need to give it a URI. The only possible problems
>with using the uri rdfs:Class for the concept currently called 'owl:Class' in
>OWL DL are eliminated by the syntactic restrictions.
>
>I would like you to exhibit a test case of an entailment that would hold in
>OWL Full, but not in OWL DL, which is not excluded by the preamble to the
>correspondence theorem.

Well, how about the fact that rdfs:Class is in the owl:complementOf 
owl:Class ? That is a logical tautology in OWL-full.

Pat

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Received on Saturday, 26 April 2003 17:42:47 EDT

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