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

From: Jeff Z. Pan <jpan@csd.abdn.ac.uk>
Date: Sat, 26 Jan 2008 16:59:00 +0000
Message-ID: <479B66D4.5000904@csd.abdn.ac.uk>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
CC: public-owl-wg@w3.org

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


>   
>> Comments/Further examples are welcome.
>>
>> Jeff
>>     
>
> peter
>
>   
Received on Saturday, 26 January 2008 16:59:30 GMT

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