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Re: significant problem for moving OWL to Last Call

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 27 Mar 2003 11:43:41 -0500 (EST)
Message-Id: <20030327.114341.47792719.pfps@research.bell-labs.com>
To: herman.ter.horst@philips.com
Cc: www-webont-wg@w3.org, phayes@ai.uwf.edu

From: herman.ter.horst@philips.com
Subject: Re: significant problem for moving OWL to Last Call
Date: Thu, 27 Mar 2003 17:12:39 +0100

> >From my earlier rdf-comments-discussion about the 
> last call version of the RDF Semantics document, I know that
> Pat sees IC and ICEXT as add-ons, just as Peter wants them to see
> (and as I also want them to see).
> 
> Note that in the text Peter cites,
> 
> >       An rdfs-interpretation of V is an rdf-interpretation 
> >       I of (V union rdfV union rdfsV) *with a distinguished subset IC 
> >       of the universe and a mapping ICEXT from IC to the set of 
> >       subsets of IR*, which ...
> 
> IC and ICEXT are not put *into* the tuple that forms I.
> I believe they are listed here as add-ons.

I believe that this wording makes it very clear that IC and ICEXT form
part of an rdfs-interpretation.  I believe that this change was made on
your suggestion.  If you instead want IC and ICEXT to be instead defined
from an rdfs-interpretation, I suggest that you notify Pat directly.

> But the possibility of such confusion should be excluded.
> 
> The following modification of the text that Peter proposed below
> does not only exclude this possibility of confusion, but also
> seems to keep the intent expressed in the current editor's version
> of the RDF Semantics document.
> 
>         An rdfs-interpretation of V is an rdf-interpretation I of (V union
>         rdfV union rdfsV) which satisfies the following semantic 
> conditions
>         and all the triples in the subsequent table, called the RDFS
>         axiomatic triples.  For convenience, and to make the semantic
>         conditions easier to understand, 
>         the set of classes IC is defined as
>                 IC = { y | <y,I(rdfs:Class)> is in IEXT(I(rdf:type)) }
>       and the function ICEXT from IC into the powerset of IR is
>       defined, for each x in IC, as
>                 ICEXT(x) = { y | <y,x> is in IEXT(I(rdf:type)) }.
>         This implies that
>                 IC = ICEXT(I(rdfs:Class)).
> 
> In agreement with Peter, I would then also remove the other
> discussion of IC and ICEXT before the definition of an 
> rdfs-interpretation.
> And I would remove not only the second but also the first condition
> from the table (which deals with ICEXT and becomes clearly also 
> superfluous).
> 
> 
> Moreover, I believe that in [1] and [2] I listed change suggestions 
> that make the S&AS document completely consistent with this 
> version of the RDFS semantics .
> ([2] is later in the same thread, and contains a copy of the 
> essential part of [1].)
> 
> Herman
> 
> [1] http://lists.w3.org/Archives/Public/www-webont-wg/2003Mar/0209.html
> [2] http://lists.w3.org/Archives/Public/www-webont-wg/2003Mar/0232.html
> 
> 
> >Herman ter Horst just brought to my attention a significant change to the
> >RDFS semantics in the editor's version of the RDF semantics document. 
> >
> >This change involves adding new constructs to the definition of RDFS
> >interpretations as follows:
> >
> >       An rdfs-interpretation of V is an rdf-interpretation 
> >       I of (V union rdfV union rdfsV) *with a distinguished subset IC 
> >       of the universe and a mapping ICEXT from IC to the set of 
> >       subsets of IR*, which satisfies the following semantic 
> >       conditions and all the triples in the subsequent table, 
> >       called the RDFS axiomatic triples.  [Emphasis added]
> >
> >Previously RDFS interpretations used the same structure as RDF
> >interpretations, and IC and ICEXT were conveniences only.
> >
> >To track this change will require significant changes to S&AS.  I do not
> >feel that OWL can go to last call without some resolution of this new
> >issue.
> >
> >Peter F. Patel-Schneider
> >Bell Labs Research
> >Lucent Technologies
> >
> >PS:  If I had my druthers, I would change RDFS interpretations back to
> >being just like RDF interpretations as they were in the Last Call version
> >of the RDF semantics.  If a clarification is needed I would proceed
> >somewhat along the lines of defining rdfs-interpretations as
> >
> >       An rdfs-interpretation of V is an rdf-interpretation I of (V union
> >       rdfV union rdfsV) which satisfies the following semantic 
> conditions
> >       and all the triples in the subsequent table, called the RDFS
> >       axiomatic triples.  For convenience, and to make the semantic
> >       conditions easier to understand, ICEXT is defined as
> >               ICEXT(x) = { y | <y,x> is in IEXT(I(rdf:type)) }
> >       and IC is defined as
> >               IC = { y | <y,I(rdfs:Class)> is in IEXT(I(rdf:type)) }
> >       which is the same as saying
> >               IC = ICEXT(I(rdfs:Class))
> >
> >and then removing the second semantic condition.  I would also remove the
> >discussion of IC and ICEXT before the definition of an 
> rdfs-interpretation,
> >but not the discussion of a class, although minor changes would need to 
> be
> >made there.
> >
> >PPS:  Someone in the RDF Core WG may want to forward this message to the 
> WG.
> >
Received on Thursday, 27 March 2003 11:43:53 GMT

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