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Re: UPDATE: status of longer version of layering document

From: Dieter Fensel <dieter@cs.vu.nl>
Date: Wed, 13 Feb 2002 16:03:43 +0100
Message-Id: <>
To: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>, www-webont-wg@w3.org
Hi all,

as usual I completely agree with Frank. Three apologizes:

-       Peter and I had to create this document on a very difficult issue
         under high time pressure.
-       we had to spent some time on agreeing on the process
         to express our disagreement.
-       we may have been not visionary enough in a sense that
         we took RDF(S) as given because a change of it may lay
         outside the scope of our workgroup as allowed by very
         strict W3C rules.

In any case, I would love to follow Frank proposals and I would
volunteer to help Peter in integrating it in our current draft. I
understand Franks email that he is also willing to join and help

I was listening a talk of Pat Hayes during the current DAML meeting.
He propose a nice trick at the RDF level that may lead us out of the
problem without loosing the OWL and RDF Schema level alignment
of reasoning (which is the essential piece anyway).



At 12:54 AM 2/13/2002 +0100, Frank van Harmelen wrote:
>"Peter F. Patel-Schneider" wrote:
> > The *next* step, of course, is to decide on which layering approach to use.
> > I am delaying throwing out the ceremonial grenade for this next step until
> > the current document has been at least somewhat assimilated.  However, if
> > you can't wait, don't let my (unusual) reticence dissuade you.  :-)
>Discussion so far has focussed on how to salvage the first layering approach
>(same syntax, extended semantics), and rightly so in my opinion, since 
>this is the most natural option.
>1. The first fix to RDFS that would save the preferred layering option has 
>been dubbed "moving rdf:type into the meta-theory".
>Can someone clarify if this is the same as what was called "stratifying 
>RDF Schema" in earlier discussions? (ie not making rdfs:Class an instance 
>of itself). Stratifying the RDFS class-hierarchy has been explored before 
>by different authors (e.g. [1],[2],[3])
>2. The second fix to RDFS that would save the first layering option would 
>be to distinguish "asserted RDF triples" from "not-asserted RDF triples". 
>The RDF(S) model-theory would only apply to asserted triples. The triples 
>that are "only OWL syntax" would be not-asserted, would not contribute to 
>the models, and would therefore not construct paradoxes. Pat Hayes has 
>been claiming that RDF Core would seriously consider such an option. It 
>would not only solve our layering problem, but also solve the problems of 
>anybody else who tries to define other languages on top of RDF. (For 
>instance, McDermott has to resort to reification to encode 'a->b' in RDF 
>to avoid ending up with asserting 'a'. Allowing unasserted triples would 
>also solve his problem.)
>3. I think it's a shortcoming of this (otherwise excellent) document that 
>it seems to suggest that the  same-syntax/extended-semantics is not 
>obtainable. It >*is*< obtainable with any of the above fixes to RDF(S), 
>and I would strongly suggest that the document discusses them (after all, 
>its purpose is to lay out the map of all options).
>    ----
>As a PS: I'm very happy that with the highly readable requirements doc by 
>Jeff et al. and the layering options doc by Peter and Dieter this WG is 
>well on its way to produce much more readable documents than any of the 
>other W3C groups I know of.
>[1] http://sesame.aidministrator.nl/doc/rdf-interpretation.html#N1c1e48d
>[2] http://www.semanticweb.org/SWWS/program/full/paper11.pdf

WARNING: I receive more than 100 emails per day
WARNING: and brake down in answering them timely,
WARNING: if ever. Sorry, Dieter :-(
Dieter Fensel
Division of Mathematics & Computer Science,
Vrije Universiteit Amsterdam,
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Received on Wednesday, 13 February 2002 12:50:05 UTC

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