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Re: Still no paradox (was: Re: The Peter paradox isn't.)

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 22 Feb 2002 06:10:40 -0500
To: phayes@ai.uwf.edu
Cc: dieter@cs.vu.nl, www-webont-wg@w3.org
Message-Id: <20020222061040Z.pfps@research.bell-labs.com>
Here is, I think, a major point of difference between our views of how OWL
has to work. 

From: Pat Hayes <phayes@ai.uwf.edu>
Subject: Still no paradox (was: Re: The Peter paradox isn't.)
Date: Thu, 21 Feb 2002 20:23:32 -0600

[...]

> >3/ Next consider DAML+OIL restrictions.
> >
> >    If John has a child that is a Person, then John belongs to the
> >    Restriction that requires that its members have a child that is a
> >    Person.
> >
> >    <John, child, Joe>, <Joe, rdf:type, Person>
> >    |= <John, rdf:type, :_1>, <:_1, rdf:type, owl:Restriction>,
> >       <:_1, owl:onProperty, child>, <:_1, owl:hasClass, Person>
> >
> >    This is only a valid entailment if all satisfying OWL interpretations of
> >    the first two statements contain a restriction of the above form.
> 
> True, but this does not capture the intuitive meaning of your 
> example. What this says in RDF is that If John has a child that is a 
> Person, then a Restriction *exists* such that John belongs to.... 
> There is however no reason why it has to make that claim in OWL.  Why 
> would OWL want to assert the *existence* of restrictions? Thats like 
> having FOL assert the existence of its own formulae.

I claim that this precisely captures the intuitive meaning of my example.
Given an OWL KB, I need to be able to determine if an object in that KB
satisfies a restriction that is not necessarily mentioned in the KB.
I would be prepared to do this somewhat indirectly, as in 

    <John, child, Joe>, <Joe, rdf:type, Person>
    |= <John, rdf:type, :_2>, <:2, owl:sameAs?, :_1>,
       <:_1, owl:onProperty, child>, <:_1, owl:hasClass, Person>

However, I view any approach that does not come up with some way of doing
the above as fundamentally broken.

peter
Received on Friday, 22 February 2002 06:11:40 GMT

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