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RE: RDF Semantics: Interpretations and Modelling

From: Massimo Marchiori <massimo@w3.org>
Date: Tue, 4 Feb 2003 17:13:16 +0100
To: "pat hayes" <phayes@ai.uwf.edu>
Cc: <w3c-rdfcore-wg@w3.org>, Ossi Nykänen <onykane@butler.cc.tut.fi>
Message-ID: <NGBBJNKIMLOPPCFHEJEMKEKJDBAA.massimo@w3.org>

> Sure. Its kind of trivial, though. The basic RDF semantic rules for simple entailment (in
> fact for any kind of entailment except linear logics) support the rule that if A entails B
> then A entails (A and B), since A entails A trivially. The inference cited is simply a
> special case of that.
That works in logic, but it's not at all a proof of the entailment. Because, what is the "and" you are referring to?
More specifically, as said in the Bag/Alt issue text, I think you confused the "and" cited above with something you call "conjoin",
which does a straight merge, but that is not a derived operation from the entailment.
Remember the discussion we had about the presence in the RDF Model Theory of a wrong definition of merge and blank node renaming?
This is a related consequence.

So, I'll still await for a proof (no t-shirts allowed ;)
Thanks,
-M



-----Original Message-----
From: pat hayes [mailto:phayes@ai.uwf.edu]
Sent: Tuesday, February 04, 2003 4:52 PM
To: Massimo Marchiori
Cc: w3c-rdfcore-wg@w3.org; Ossi Nykänen; Massimo Marchiori
Subject: RE: RDF Semantics: Interpretations and Modelling


Pat, this reply brought to my mind a lovely Sidney Harris' t-shirt that Leslie Lamport showed me for the first time ten years ago or
so (wow, time flies....): http://www.scienceteecher.com/proof.htm
Can you please give a proof of your entailment? ;)
Thanks,
-M



Sure. Its kind of trivial, though. The basic RDF semantic rules for simple entailment (in fact for any kind of entailment except
linear logics) support the rule that if A entails B then A entails (A and B), since A entails A trivially. The inference cited is
simply a special case of that.


Can you, in turn, say why you think this is wrong?


Pat





Ossi, this is the Bag/Alt issue, raised in May 2002:

http://lists.w3.org/Archives/Public/www-rdf-comments/2002AprJun/0112.html
AFAIK never replied yet.
Incidentally, the same wrong argument pointed therein appears again in the current last call draft.



Im not sure which 'wrong argument' you are referring to. I stand by everything I said that is  included in the above-referenced
message. In particular,


" If
_:xxx [rdf:type] [rdf:Bag] .
> _:xxx [rdf:_1] <ex:a> .
> _:xxx [rdf:_2] <ex:b> .
>
> entails
>
> _:xxx [rdf:_1] <ex:b> .
> _:xxx [rdf:_2] <ex:a> .
>
> then it also must entail
>
> _:xxx [rdf:type] [rdf:Bag] .
> _:xxx [rdf:_1] <ex:a> .
> _:xxx [rdf:_2] <ex:b> .
> _:xxx [rdf:_1] <ex:b> .
> _:xxx [rdf:_2] <ex:a> .
>
> and by suitable reordering, it will entail that ALL members of the
> bag are in ALL positions."


is a correct argument, and your response to it is incorrect.


Pat






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Received on Tuesday, 4 February 2003 11:13:56 EST

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