W3C home > Mailing lists > Public > www-webont-wg@w3.org > April 2002

RE: Moving forward

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Mon, 8 Apr 2002 03:20:10 -0400
Message-Id: <p0510151bb8d5153b42d6@[65.217.30.94]>
To: "Jeremy Carroll" <jjc@hplb.hpl.hp.com>
Cc: www-webont-wg@w3.org
>  > >One way to go would be to
>>  >1/ ask for ``unasserted'' stuff in RDF
>>  >2/ place restrictions on the form of the DAML+OIL constructs
>
>
>Pat:
>>  I am confident that this will be a viable solution. Existing code
>>  does this, in effect, and seems to work reliably, and there is a
>>  clear strategy for providing a coherent semantics. I do not even
>>  think that it will require significant changes to DAML+OIL; the only
>>  extra requirement is that the daml:list triples be unasserted in RDF.
>>  It has some risks, the chief of which is that legacy RDF code which
>>  does not respect the 'unasserted' distinction might produce OWL
>>  inconsistencies. I think this is at worst an interim problem which
>>  will go away by itself, but we should consider it carefully.
>
>
>
>
>Pat
>
>maybe I am asking too much at that stage ... but here goes.
>
>How do unasserted triples fit into a model theory?

They are already in the RDF MT. All that is needed is some way to 
recognise them syntactically. Technically, they are not required to 
have any truthvalue, so putting them into a graph doesn't impose any 
constraint on the interpretations.

>Consider
>
><foo> owl:oneOf [ <foo> ] .
>
>I'll start each line with an 'a' or a 'u'
>
>a <foo> <rdf:type> _:t .
>a _:t  <owl:oneOf> _:l .
>u _:l <rdf:type> <owl:List> .
>u _:l <owl:first> <foo> .
>u _:l <owl:rest> <owl:nil> .
>
>I don't see how the bit in the first column helps in the model theoretic
>interpretation here.

Well, it *alters* it, in that a satisfying interpretation is only 
required to make the first two triples true. So for example an 
interpretation in which the extension of <owl:first> does not contain 
the pair <I(_:l),I(<foo>)> might satisfy this RDF graph. Of course, 
such an RDF interpretation might well not be a satisfying OWL 
interpretation, but then that is what one would expect in a layering 
situation. So this means that a satisfying OWL interpretation has be 
an extension of an RDF interpretation *of the first two triples 
only*. It isnt required to be an extension of an interpretation in 
which there is a thing denoted by the owl:List bnode, for example.

>(Feel free to change any of the bits in any explanation - they are just my
>guesses as to what is being proposed).
>
>I assume that the above is 'true' in some sense, where
>
><foo> owl:oneOf [ <bar> ] .
>
>is 'false' in the same sense.
>
>I can make that so in my solipsistic system, without any unasserted triples.

I'm afraid that I am unable to understand your solipsistic stuff, at present.

Pat

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Received on Monday, 15 April 2002 10:57:31 GMT

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