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

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
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Vorstand: Rüdiger Dillmann, Michael Flor, Jivka Ovtcharova, Rudi Studer
Vorsitzender des Kuratoriums: Ministerialdirigent Günther Leßnerkraus