- From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
- Date: Mon, 11 Aug 2008 20:18:35 +0100
- To: Jim Hendler <hendler@cs.rpi.edu>
- Cc: Michael Schneider <schneid@fzi.de>, "public-owl-wg Group WG" <public-owl-wg@w3.org>
Jim, It is true that some details, particularly those related to conformance, still need to be precisely specified, but it seems to me that the unification proposal makes everything much less confused: there would be just one rules profile (now called OWL-RL), and it would behave in pretty much the way you describe below. In particular, the unification proposal is designed to *avoid* the craziness of a third semantics, which is exactly what we would have if we left things as they are. Ian On 8 Aug 2008, at 17:42, Jim Hendler wrote: > > 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 Tuesday, 12 August 2008 08:39:44 UTC