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Re: Action-67 some examples on b-nodes issues and their impact on users

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Sat, 26 Jan 2008 11:36:28 -0500 (EST)
Message-Id: <20080126.113628.62222588.pfps@research.bell-labs.com>
To: jpan@csd.abdn.ac.uk
Cc: public-owl-wg@w3.org

From: "Jeff Z. Pan" <jpan@csd.abdn.ac.uk>
Subject: Re: Action-67 some examples on b-nodes issues and their impact on users
Date: Sat, 26 Jan 2008 16:59:00 +0000

> Peter F. Patel-Schneider wrote:
> > From: "Jeff Z. Pan" <jpan@csd.abdn.ac.uk>
> > Subject: Re: Action-67 some examples on b-nodes issues and their impact on users
> > Date: Fri, 25 Jan 2008 21:44:52 +0000
> >
> >   
> >> Hi Peter, Ivan, Bijan,
> >>
> >> Thanks for joining the discussions. It seems that we also need an 
> >> example to illustrate the difference of the two semantics in terms of 
> >> entailment checking.
> >>
> >> Let me extend the example as follows. Given an ontology O (about 
> >> friends) which consists of the following axioms:
> >>
> >> hasFriend(Bob,Chris)
> >> hasFrinnd(Bob,:_1)
> >> hasAge(:_1,"26"^^xsd:integer)
> >>
> >> Now the question is to check if O entails that Bob has at least two friends.
> >>
> >> - Under semantic 1) (existentially quantified variables), the answer of 
> >> the above entailment checking is false.
> >>
> >> - Under semantic 2) (skolem constants), the answer of the above 
> >> entailment checking is true.
> >>     
> >
> > I don't think that this (2) is correct.
> >
> > I don't see anything in the above ontology under any reasonable reading
> > of skolemization of bnodes that would indicate that the skolems
> > necessarily have a different denotation than existing constants do.
> > Therefore there is no reason to infer that Bob has two friends.
> >   
> 
> It seems that, in order to make the extended example work, we need to 
> have unique name assumption.
> 
> Jeff

Umm, how would this make the extended example work?  In any case the
Unique Name Assumption is not part of OWL.  I don't think that adding it
to OWL would be a good idea.

peter
Received on Saturday, 26 January 2008 17:06:23 GMT

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