- From: Smith, Michael K <michael.smith@eds.com>
- Date: Thu, 15 May 2003 11:36:58 -0500
- To: Jim Hendler <hendler@cs.umd.edu>, Jeremy Carroll <jjc@hpl.hp.com>, www-webont-wg@w3.org
I am happy to add "desirable computational properties" to the species description of Lite in the Guide. But I am a little hesitant regarding "maximal decidable subset, although subject to a higher worst-case complexity". Has anyone demonstrated that that DL is the maximal decidable subset of Full? The DL text currently says: > OWL DL supports those users who want the maximum expressiveness > without losing computational completeness (all entailments are > guaranteed to be computed) and decidability (all computations will > finish in finite time) of reasoning systems. Which seems to pretty much capture the intent. ?? - Mike Michael K. Smith, Ph.D., P.E. EDS - Austin Innovation Centre 98 San Jacinto, #500 Austin, TX 78701 phone: +01-512-404-6683 email: michael.smith@eds.com -----Original Message----- From: Jim Hendler [mailto:hendler@cs.umd.edu] Sent: Wednesday, May 14, 2003 7:11 AM To: Jeremy Carroll; www-webont-wg@w3.org Subject: Re: Proposed response to Martin Merry, HP (note - there is a suggestion to editors for some wording changes to Ref and Guide in this message - it is before the section marked personal opinion) At 8:44 AM +0300 5/14/03, Jeremy Carroll wrote: >In >http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0181.html > >DanC: >> On closer examination of the comment, it seems >> to be more about what goes in OWL DL than >> what goes in OWL Lite. > >And in ... >http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0174.html >DanC: >>Please help me find the relevant decisions >>and/or find evidence that those implementations >>pass some relevant tests and/or add an >>issue to the issues list. > >In January, we agreed a definition of a "complete OWL DL consistency checker", >if we had evidence that such a thing existed, and/or that more than one would >exist in the future (and the WG was satisfied that they would be practically >usable, rather than essentially theoretical exercises) then we could respond >with a message that indicated that, and that we thought that that was >sufficient to justify the DL level. > >If we don't have such evidence then I agree with >http://lists.w3.org/Archives/Public/www-webont-wg/2003May/0181.html > >DanC: >> Mr. Merry's point, "We're concerned that OWL users should have their >> expectations met when they use OWL compliant systems." seems well >> made, no? So let's set their expectations correctly -- we did try, by the way - in Reference, section 8.2 we say: In particular, the OWL DL restrictions allow the maximal subset of OWL Full against which current research can assure that a decidable reasoning procedure can exist for an OWL reasoner. and in 8.3 we say The limitations on OWL Lite place it in a lower complexity class than OWL DL. This can have a positive impact on the efficiency of complete reasoners for OWL Lite. In fact, my original response to Mr. Merry was going to be that we had already addressed his comments and point out these quotes --- However, his comments and a couple of others we received show that we haven't made the difference clear ENOUGH in our documents. (For example, in section 1.2 we don't mention the computational issue). I therefore suggest that editing Ref and Guide to set expectations is the correct solution - consistent w/WG decisions in the past. One we could fix ref, is to make it clear that the difference between OWL Lite and OWL DL with respect to this computational issue is there. For example, when we first introduce Lite in section 1.2 of ref we say: OWL Lite is particularly targeted at tool builders, who want to support OWL, but want to start with a relatively simple basic set of language features. instead of saying it is known to have a relatively efficient decision procedure (and citing the literature). Maybe simply adding a sentence after the one I cite above that says "In addition, OWL Lite is designed based to fit into a known computational class that, while exponential, is lower than the complexity of OWL DL [cite something]" I also think the "Species of OWL" section of the Guide is also less clear than it could be, and might be wordsmithed to make the issue clearer (for example, OWL Lite could say "Desirable computational properties" and OWL DL could say "maximal decidable subset, although subject to a higher worst-case complexity") Guus, Mike S -- would making these edits be acceptable? If so, I would include in the response to Merry and to the other similar issues. <PERSONAL OPINION> >(A danger is that if OWL DL is tainted then the whole OWL brand is tainted). >>Jeremy What I would say would make OWL DL "tainted" would be to remove oneOf and hasValue. hasValue is used in about 10% of the ontologies in the DAML ontology library, and oneOf, although not heavily used in that library, is IMHO necessary for mapping existing sources into ontologies --my group has used it in many cases where we have used either an XML schema or a database schema as the basis of an ontology, especially in our work with Web Service Composition [1]. I would also remind the group that we actually had support in the WG to put hasValue in Lite, but decided not to due to the computational issue. I would argue strongly that it is better to explain things more clearly in our documents than to change the language. We spent a long time developing a language that is well balanced for many considerations, and I'd like to see if used in practice before we start cutting useful features because of computational issues that may rarely or never arise in real applications. For instance, PARKA-DB [2], still the fastest ontology management system deployed to date, is in the same complexity class as OWL DL, but somehow people don't seem to mind since it can answer most useful queries in a few milliseconds against ontologies with tens of thousands of classes - it has a worst case time that could be in several minutes for the largest ontologies built yet - but that doesn't seem to matter since after 5 seconds it asks the user if they want to continue, and most people say "no" and reformulate the query... Quoting one of our comment raisers, speaking about OWL: At 11:43 PM -0400 5/9/03, Bijan Parsia wrote in [3]: 4) Get the damn thing out the door. </PERSONAL OPINION> [1] http://www.mindswap.org/papers/composition.pdf [2] http://www.cs.umd.edu/projects/plus/Parka/aaai97.ps [3] http://lists.w3.org/Archives/Public/public-webont-comments/2003May/0069.html -- Professor James Hendler hendler@cs.umd.edu Director, Semantic Web and Agent Technologies 301-405-2696 Maryland Information and Network Dynamics Lab. 301-405-6707 (Fax) Univ of Maryland, College Park, MD 20742 240-731-3822 (Cell) http://www.cs.umd.edu/users/hendler
Received on Thursday, 15 May 2003 12:37:14 UTC