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

From: Ivan Herman <ivan@w3.org>
Date: Wed, 23 Jan 2008 10:24:04 +0100
Message-ID: <479707B4.1020606@w3.org>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
CC: jpan@csd.abdn.ac.uk, public-owl-wg@w3.org

Peter F. Patel-Schneider wrote:
>> Example:
>> Given an ontology O about friends (suppose there are no anonymous
>> individuals in O). Let us consider the following extra individual
>> axioms (where :_1 is an anonymous individual):
>> hasFriend(Bob,:_1)
>> hasAge(:_1,"26"^^xsd:integer)
>> With both semantics, the axioms both roughly say "Bob has some
>> friend aged 26" with some subtle difference: under semantics 1),
>> the friend aged 26 could be someone already mentioned in O, while
>> under semantics 2), the friend is someone new and cannot be
>> someone mentioned in O.
> I do not believe that this is an accurate English gloss of the actual
> formal situation.
> [I'm going to use an FOL syntax below to emphasize the difference
> between the two situation.]
> If we have a KB that does not mention some constant, say fB, then the
> difference between 
> 	Ex hasFriend(Bob,x) & hasAge(x,26)
> and
> 	hasFriend(Bob,fB) & hasAge(fB,26)
> is not that fB is or is not equal to any other constant in the KB.
> With only the above information, there would be interpretations in which
> the denotation of x is the same as the denotation of some (other)
> constant and interpretations where the denotation of x is different from
> that of all (other) constants and similarly for fB.


I must admit I have some difficulties to fully parse this sentence, 
primarily the 'and similarly for fB' part. Sorry, I am not versed in 
logic as you are... Can you expand the difference between the two a 
little bit more?

Thanks a lot


>> (The above is true unless we have some further extra axioms
>> forcing :_1 to be the same as some known individuals.)
>> Comments/Further examples are welcome.
>> Jeff
> peter


Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
PGP Key: http://www.ivan-herman.net/pgpkey.html
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Received on Wednesday, 23 January 2008 09:24:21 UTC

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