W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > September 2002

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>
Message-ID: <BHEGLCKMOHGLGNOKPGHDKEDJCAAA.jjc@hpl.hp.com>



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

http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Jun/0229.html

In fact that thread is quite interesting:

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

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

PatH:
[[
In fact, your entailments aren't even
valid, because two different classes can have the same class
extension.
]]

PatH:
[[
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 ...

Jeremy




> -----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
> --
> ---------------------------------------------------------------------
> IHMC					(850)434 8903   home
> 40 South Alcaniz St.			(850)202 4416   office
> Pensacola,  FL 32501			(850)202 4440   fax
> phayes@ai.uwf.edu
> http://www.coginst.uwf.edu/~phayes
>
>
Received on Thursday, 19 September 2002 06:04:26 EDT

This archive was generated by hypermail pre-2.1.9 : Wednesday, 3 September 2003 09:51:00 EDT