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Re: ISSUE-131 (OWL R Unification): Fundamental understanding problems

From: Jim Hendler <hendler@cs.rpi.edu>
Date: Fri, 8 Aug 2008 12:42:10 -0400
Cc: "public-owl-wg Group WG" <public-owl-wg@w3.org>
Message-Id: <7807FC8B-8543-4E8C-817E-BAF116A87F6C@cs.rpi.edu>
To: Michael Schneider <schneid@fzi.de>

Having left the WG, I seem to still be being pulled in a lot by side  
emails, so let me state, as RPI AC rep, that we agree with Michael  
that as yet this is not specified to the point where we know for sure  
what it means, but given the spirit of the initial emails, we are  
troubled.  The reasons were well stated by Ivan.  It seems to me that  
this WG is going to great lengths to sow confusion between a simple  
meaning of DL vs. Full, instead of the relatively straightforward way  
it was resolved in the first WG.  Roughly speaking, we would like to  
see a solution where the rules, applied to an OWL DL ontology would  
produce and OWL DL ontology (thus OWL R would be "DL compliant"  
whatever that means) and that a "full implementation of OWL R DL"  
would be expected to match the DL semantics.  We would expect that the  
same set of rules, applied to an OWL Full ontology (defined at the  
moment as something that includes some feature outside OWL DL) would  
do the same -- i.e. would produce a new ontology not expected to be in  
OWL DL and if it didn't include all the expected inferences, as  
defined by the rules, it would not be considered a "full  
implementation of OWL R" -- I don't understand this craziness about  
needing a third semantics, nor do I understand why OWL R is not just  
OWL R.
  Frankly, this WG seems very confused as to what OWL DL and Full  
should/could be, and I think the proposals with respect to the  
renaming, the addition of odd triples, and this so-called unification  
will make this confusion even worse.
   -Jim H.

On Aug 7, 2008, at 8:23 PM, Michael Schneider wrote:

> Dear all,
>
> in spite of a lot of discussion, which has happened on the unification
> issue, both in the mailing list and at meetings, and additional  
> discussions
> which I had privately with WG members, I stronger than ever have the  
> feeling
> that I do not understand what the unification will actually look  
> like in the
> end. So I would like to hear from other WG members what they believe  
> will be
> the result.
>
> Below, I have assembled a list of assumptions, which represent my  
> current
> understanding. These points can, in the simplest case, be answered  
> with
> "yes" or "no". But in the case of "no", I would appreciate to hear  
> from you
> what your understanding is instead.
>
> Please keep in mind that I am really only interested in  
> understanding how
> exactly OWL R will be specified in the end. This means, essentially,  
> that I
> want to know what the syntax and what the precise semantics of OWL R  
> will
> be, and also, what the exact role of the OWL R ruleset will be for  
> OWL R.
>
> (On the other hand, I am *not* interested in, for example, the  
> question when
> may or should an OWL R reasoner signal a warning to a user, since  
> such an
> implementation-specific behavior is completely outside the formal
> specification of a language.)
>
>
> Here is the list of my current assumptions:
>
> (A) The "syntactic fragment" of the unified OWL R language will be  
> defined
> by today's syntax of OWL R DL, as specified in sec 4.2 of the Profiles
> document. An ontology will be called a "valid OWL R ontology", if it  
> matches
> these syntactic restrictions.
>
> (B) Nothing specific is said about ontologies which do not fall in  
> this
> syntactic fragment, so an OWL R compliant reasoner is free to either  
> deny or
> accept such an ontology as syntactically valid input.
>
> (C) For ontologies matching the syntactic fragment, the OWL R  
> semantics of
> such an ontology will be specified in parallel by the OWL DL  
> semantics (as
> it is nowadays true for OWL R DL), and also w.r.t. the ruleset of  
> today's
> OWL R Full.
>
> (D) For (C) to make sense, the DL semantics and the rule based  
> semantics
> have to be exactly equivalent for ontologies matching the syntactic
> fragment. It is believed that this relationship holds. For ontologies
> outside the syntactic fragments, this equivalence is *not* required  
> to hold.
>
> (E) For ontologies outside the syntactic fragment, the only semantic
> restriction on reasoners is that they must not produce inferences  
> which go
> beyond OWL Full (without "R"!) entailment. So they may produce  
> whatever
> inferences they like, as long as they keep being in the scope of OWL  
> Full.
> In particular, they MAY produce all or only some of the inferences  
> which can
> be derived from the OWL R ruleset for such ontologies, but this will  
> in no
> way be enforced by the specification or OWL R.
>
>
> Regards,
> Michael
>
> --
> Dipl.-Inform. Michael Schneider
> FZI Forschungszentrum Informatik Karlsruhe
> Abtl. Information Process Engineering (IPE)
> Tel  : +49-721-9654-726
> Fax  : +49-721-9654-727
> Email: Michael.Schneider@fzi.de
> Web  : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555
>
> FZI Forschungszentrum Informatik an der Universität Karlsruhe
> Haid-und-Neu-Str. 10-14, D-76131 Karlsruhe
> Tel.: +49-721-9654-0, Fax: +49-721-9654-959
> Stiftung des bürgerlichen Rechts
> Az: 14-0563.1 Regierungspräsidium Karlsruhe
> Vorstand: Rüdiger Dillmann, Michael Flor, Jivka Ovtcharova, Rudi  
> Studer
> Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus
>

"If we knew what we were doing, it wouldn't be called research, would  
it?." - Albert Einstein

Prof James Hendler				http://www.cs.rpi.edu/~hendler
Tetherless World Constellation Chair
Computer Science Dept
Rensselaer Polytechnic Institute, Troy NY 12180
Received on Friday, 8 August 2008 16:42:48 GMT

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