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Re: Two questions about bagid

From: Tim Berners-Lee <timbl@w3.org>
Date: Tue, 11 Feb 2003 16:05:13 -0800
Cc: RDF Core <w3c-rdfcore-wg@w3.org>
To: Jan Grant <Jan.Grant@bristol.ac.uk>
Message-Id: <A8980196-3E1D-11D7-84BF-000393914268@w3.org>


On Tuesday, Feb 11, 2003, at 14:46 US/Pacific, Jan Grant wrote:

> On Tue, 11 Feb 2003, Tim Berners-Lee wrote:
>
>> Another question is about the semantics.
>> I understand that an id  :i  on the statement  { :superman :can :fly}
>> should generate the statements
>>
>> :i a rdf:Statement;  rdf:subject :superman;   rdf:predicate :can;
>> rdf:object :fly.
>> :superman :can :fly.
>>
>> and I might want to use this to generate attribution:
>>
>> :lois :thinks :i.
>>
>> This would suggest that an owl reasoner (say) that knows that 
>> :superman
>> and
>> :clarkekent are daml:equivalent should be able to infer that
>>
>> :i a rdf:Statement;  rdf:subject : clarkekent;   rdf:predicate :can;
>> rdf:object :fly.
>> : clarkekent :can :fly.
>> :lois :thinks :i.
>>
>> This seems counterintuitive, as one would expect it allow one to
>> conclude
>> that the modified statement is due to the original source.
>> Some form of quoting around the subject, predicate
>> and object would seem necessary.
>
> I've had this conversation with Danbri before. The owl reasoner you
> posit has superman and clarkkent denoting the same thing (ie, it 
> applies
> an interpretation that a comic reader would agree with). Strictly
> speaking, from the comic reader's point of view (ie, in that
> interpretation) the conclusion is correct: Lois thinks that the person
> denoted by "Clark Kent" can fly, which he can, 'cause he's super.

No, she doesn't know that.   She doesn't know that "Clark Kent"
denotes Superman. She doesn't think Clark Kent can fly.


> Lois wouldn't reason using the same interpretation, so her conclusions
> would be different.

However, I thought that the idea of the [bag]id was to show the 
attribution
of the information.  The semantics were that Lois think that clarkkent
can fly, or we believe the information because we got it from Lois.
This is misrepresenting the situation.  Either that, or the [bag]id
has some semantics I have misunderstood.  But i had assumed the attempt
was to say (in N3)

:lois :thinks { :superman :can :fly }.
:superman = :clakkent.

which does NOT permit one to conclude
:lois :thinks { : clakkent :can :fly }.

> -- 
> jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/
> Tel +44(0)117 9287088 Fax +44 (0)117 9287112 http://ioctl.org/jan/
> I am now available for general use under a modified BSD licence.
Received on Tuesday, 11 February 2003 19:04:33 EST

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