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Re: Possible semantic bugs concerning domain and range

From: pat hayes <phayes@ai.uwf.edu>
Date: Fri, 25 Oct 2002 11:48:24 -0500
Message-Id: <p05111b01b9df23d13d63@[65.217.30.130]>
To: Ian Horrocks <horrocks@cs.man.ac.uk>
Cc: www-webont-wg@w3.org

>On October 24, pat hayes writes:
>>
>>  >There may be pragmatic/implementation reasons to go for implies
>>  >semantics in all cases:
>>  >
>>  >- it can only lighten the burden on implementors as there will be
>>  >fewer kinds of logical entailment to worry about.
>>  >
>>  >- the cost isn't very great as implied functionality, transitivity
>>  >etc. due to strange constraints on possible models doesn't seem like
>>  >it would be of great interest.
>>  >
>>  >- it would satisfy Pat's complaint that logically entailed range and
>>  >domain restrictions are positively harmful.
>>
>>  But it would fail to satisfy the RDFS requirement that subClassOf and
>>  subPropertyOf are transitive. We could of course just add this as an
>>  ad-hoc semantic requirement, but that seems very tacky.
>
>I'm not sure what your point is here. Are you concerned as to whether
>subClassOf and subPropertyOf are implicitly instances of
>owl:TransitiveProperty? I do not believe that this would not be a
>valid Fast OWL inference (or at least not a question one could ask).

No, its purely an RDFS matter. The RDFS spec requires that the RDFS 
semantics impose the condition that rdfs:subClassOf and 
rdfs:subPropertyOf are transitive. Of course you cannot SAY this in 
RDFS, but it is nevertheless required. The 'IF' semantics does not 
guarantee that the subClass/Property relations are transitive, as 
Peter noticed a while back.

This would indeed presumably mean that

rdfs:subClassOf rdf:type owl:TransitiveProperty .

would be valid in OWL. (Even fast OWL. right?).

>
>>  Given the option between all IF and all IFF, I think the all-IFF
>>  option is more coherent. But I would prefer a more tailored solution,
>>  as you know.
>
>I prefer all IF for the reasons I have mentioned, in particular the
>possible extra burden on implementors. E.g., it isn't clear that these
>entailments can be reduced to satisfiability and still stay within OWL
>Lite (it might be possible, but not via the reductions we have
>mentioned up to now as these rely on nominals), so these entailments
>might make it harder to implement a complete OWL Lite reasoner.

Hmmm. But these are definitely required for RDFS, so this may be an 
issue for OWL Lite to look at more seriously. I don't think that it 
would be kosher for OWL lite to assume that part of the meaning of 
any RDFS term was, as it were, removed in OWL.

Pat
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Received on Friday, 25 October 2002 12:48:27 GMT

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