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

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@[]>
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.

IHMC					(850)434 8903   home
40 South Alcaniz St.			(850)202 4416   office
Pensacola              			(850)202 4440   fax
FL 32501           				(850)291 0667    cell
phayes@ai.uwf.edu	          http://www.coginst.uwf.edu/~phayes
Received on Friday, 25 October 2002 12:48:27 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 21:56:48 UTC