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RE: Technical change to the RDFS MT

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Thu, 19 Sep 2002 12:04:19 +0200
To: "pat hayes" <phayes@ai.uwf.edu>, <w3c-rdfcore-wg@w3.org>

I don't think this is a big deal either way, but note that you argued
against this in


In fact that thread is quite interesting:

If rdfs:subClassOf is pronounced
"rdfs:subSETOf" then we ought to consider fixing the spelling.

Which part of our
spec allows you to conclude the rdfs:range triple?

In fact, your entailments aren't even
valid, because two different classes can have the same class

That would be disastrous for the datatyping and in any case not
make sense.

At the time I was somewhat persuaded by Peter's view ...


> -----Original Message-----
> From: w3c-rdfcore-wg-request@w3.org
> [mailto:w3c-rdfcore-wg-request@w3.org]On Behalf Of pat hayes
> Sent: 18 September 2002 23:01
> To: w3c-rdfcore-wg@w3.org
> Subject: Technical change to the RDFS MT
> Guys,
> Recent attempts (in collaboration with Peter and Ian) to reconcile
> the RDF(S) MT with the emerging OWL MT have suggested that it would
> be good to make a technical alteration to the semantic conditions for
> RDFS. I think that this change will make no appreciable difference to
> RDFS itself (ie it will give the same RDFS entailments), but am
> soliciting comments on this change from the WG before deciding to do
> it.
> We can illustrate the point by considering rdfs:subClassOf. Right
> now, we say that
> A rdfs:subClassOf B
> is true in I  if ICEXT(I(A)) is a subset of ICEXT(I(B)). Which seems
> kind of obvious; but the idea is to change this to read " ... is true
> in I IFF  ... " , i.e. make the semantic conditions *necessary and
> sufficient* for the truth of the triple.
> The reason this doesnt make any appreciable difference to RDFS is
> that RDFS has no notion of negation, so it doesnt really matter if it
> treats something as false when its really true, which would be
> possible in the current MT: that is, you could (currently) have two
> classes and one class extension be a subset of the other, and still
> count rdfs:SubClassOf as being false in that interpretation. That
> wouldnt matter since that interpretation wouldnt satisfy any
> antecedents that might trigger a wierd conclusion, since it just
> fails to make something true. But when we go to OWL, there is
> something like a negation (owl:complementOf), and so now this
> possible mismatch between what is actually correct in the
> interpretation and what triples the interpretation makes true
> suddenly starts to matter, both ways round.
> Similar changes need to be made to the conditions for
> rdfs:subPropertyOf and the domain and range conditions, for similar
> reasons.
> Unless anyone objects, I plan to make this change in the next (and
> hopefully close-to-final) version. So object now or forever hold your
> piece. (To emphasize, this change makes the MT *more* conventional
> rather than less, ie this is the standard way to do it)
> Pat
> --
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Received on Thursday, 19 September 2002 06:04:26 UTC

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