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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 07:32:18 -0500 (EST)
Message-Id: <20080126.073218.159517037.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: 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.

> Comments/Further examples are welcome.
> 
> Jeff

peter
Received on Saturday, 26 January 2008 13:02:20 GMT

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