- From: Guus Schreiber <schreiber@cs.vu.nl>
- Date: Wed, 14 May 2003 16:44:17 +0200
- To: Jim Hendler <hendler@cs.umd.edu>
- CC: www-webont-wg@w3.org
Jim Hendler wrote: > (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 agree with this change. Also, I think the sentence earlier in this section (1.2) on OWL DL needs to be changed (as Dan also pointed out). It currently says: [[ The main reason for having the OWL DL sublanguage is that tool builders have developed powerful reasoning systems which support ontologies constrained by the restrictions required for OWL DL. ]] This requires some form of not pointing to the issues discussed by Ian in his December message on complexity: http://lists.w3.org/Archives/Public/www-webont-wg/2002Dec/0239.html I wouldn't mind incorporating Ian's message in some (edited) form into Ref, e.g. as extended note, as a new Sec. 8.4 (probably my preference) or as appendix. Guus > 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 > > -- NOTE: new affiliation per April 1, 2003 Free University Amsterdam, Computer Science De Boelelaan 1081a, 1081 HV Amsterdam, The Netherlands Tel: +31 20 444 7739/7718 E-mail: schreiber@cs.vu.nl Home page: http://www.cs.vu.nl/~guus/ [under construction]
Received on Wednesday, 14 May 2003 10:44:21 UTC