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Re: LBase in the RDF Semantics Doc

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 15 May 2003 08:19:32 -0400 (EDT)
Message-Id: <20030515.081932.03868230.pfps@research.bell-labs.com>
To: bwm@hplb.hpl.hp.com
Cc: www-rdf-interest@w3.org

[I note that the version of L[B]ase: Semantics for Languages of the
Semantic Web by Guha, R. V. and Hayes, P. of November 2002 is no longer

From: Brian McBride <bwm@hplb.hpl.hp.com>
Subject: LBase in the RDF Semantics Doc
Date: Thu, 15 May 2003 09:41:13 +0100

> The RDF Semantics document specifies the formal semantics of RDF(S).  It 
> includes an informative appendix
>    http://www.w3.org/TR/rdf-mt/#Lbase
> which restates the semantics in the form of a small set of axioms.  

Actually, this appendix does not do this.  The Appendix is a translation
from RDF graphs to sets of LBase formulae.  Three sets of LBase formulae
(RDF axioms, RDFS axioms, and RDF-D axioms) are also given.  The axioms by
themselves do not provide a semantics for RDF.

> The 
> intent is that this representation is easier to understand.

The only statement to this effect is in the Introduction

    ... and may be more readable.

> RDFCore have had a last call comment suggesting this appendix be removed:
>    http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0092.html

I view this description of my comment as incorrect.  Nowhere in my comment
is there a request or even a suggestion to remove the appendix, only that
there is currently no point to the appendix.  This does imply, of course,
that without any significant change to the appendix it would be much better
to remove the appendix than to leave it in.

Other remedies are possible.  For example, it would be possible to provide
a point to the appendix by stating that the translation preserves some
particular important aspect of the RDF semantics, such as satisfiability,
entailment, or some aspect of models.  A proof that the translation does
preserve this property should probably then be provided.  

If the point of the translation is only to provide some intuitive,
not-necessarily-complete-or-even-correct notion of the meaning of RDF, then
a translation to a more-standard formalism would be better.

> It would be helpful in resolving this comment, for the WG to have feedback 
> on whether or not folks find this appendix useful.
> Brian

In its current form, I find the appendix to be detrimental.

Peter F. Patel-Schneider
Bell Labs Research
Lucent Technologies
Received on Thursday, 15 May 2003 08:19:44 UTC

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