- From: Jim Hendler <hendler@cs.rpi.edu>
- Date: Tue, 12 Aug 2008 08:19:01 -0400
- To: Jim Hendler <hendler@cs.rpi.edu>
- Cc: Bijan Parsia <bparsia@cs.man.ac.uk>, "Michael Schneider" <schneid@fzi.de>, "Ian Horrocks" <Ian.Horrocks@comlab.ox.ac.uk>, <public-owl-wg@w3.org>
Oops - apologies to the WG, didn't mean to send this to the whole group - accidently hit the reply-all, JH On Aug 12, 2008, at 8:13 AM, Jim Hendler wrote: > > Bijan- before you accuse Michael of making a point for "debate" I > suggest you check the logs -- the idea of a rule-based fragment per > se was raised by me in the context of what we were then calling RDFS > 3.0, and it was distinct from the DLP-oriented solutions (very > distinct). The WG over time pushed these two together, causing the > problems Michael is trying to solve. The log is pretty clear on > this -- and I have the scars to prove it... > > > On Aug 12, 2008, at 4:00 AM, Bijan Parsia wrote: > >> >> On Aug 12, 2008, at 1:08 AM, Michael Schneider wrote: >> >>> Hi Ian! >>> >>> Ian Horrocks wrote: >>> >>>> Michael, >>>> >>>> It has never been claimed that OWL R DL and OWL R Full are >>>> completely >>>> equivalent on the syntactic fragment. >> [snip] >>> In the original issue, it was stated that >>> >>> "The main benefit would be that we would not need >>> owl:intendedProfile" >>> >>> For me, this is at best a very minor nice-to-have benefit. >> >> That's not the main benefit for *me*. The main benefits are: >> 1) Profiles all (mostly) work the same (i.e., the core bit is a >> syntactic fragmetn) >> 2) Extensibility on the semantics makes sense (i.e., tools aren't >> *forced* to be semantically restricted outside ethe core fragment) >> 3) We don't have axioms which have semantically meaningful >> constructs only on one side. >> >> For me 1 and 3 are *killers*. >> >>> And now, we are near to close this "intended profile" issue, >>> anyway, by not having such a signaling URI at all. So, the >>> "unification" issue can even be regarded to be kind of moot. >> >> No. >> >>> But we are still talking about the unification, for which the >>> price to pay would be pretty high for the RDF side, which >>> originally was the only side that asked for such a rule-based >>> language. >> >> First, this isn't true. DLP was included in the original fragments >> document, IIRC. Please don't rewrite history esp. to make a >> debater's point. >> >> Second, we have to consider the ecosystem, not just a single >> species. We also have to consider the range of users and the range >> of possible confusions. >> >> We're adding a *lot* of real constructs to an RDF fragment...we >> should expect that people will be less indifferent to the >> entailments they get. >> [snip] >>>> Your example is a good illustration of why it would be *a very bad >>>> idea* to define a 3rd semantics for OWL based on the OWL RL rules. >>>> According to this semantics, it would NOT be the case that >>>> owl:intersectionOf (C D) is a subClassOf D. Any reasoner finding >>>> this >>>> entailment would be unsound and non-conformant w.r.t. this >>>> semantics. >>>> This would, IMHO, be highly counter-intuitive. >>> >>> Now this was actually my counter example, so one can easily take >>> it as an example for an "unintuitively" missing entailment. But >>> equally well, from a rules perspective, one could also claim that >>> producing this entailment is counter intuitive. >> >> What? Are you seriously coming from a user perspective *at all*? >> They aren't going to look at the rules. They are going to *write >> something down*. >> >>> Actually, there are enough examples for derivations by applying >>> the rules, where there is no respective entailment by OWL R DL, >>> simply because it would fall outside OWL R DL's syntax (at least, >>> an OWL R DL reasoner wouldn't be required to produce it there). >>> >>> Consider that very asymmetric syntax of OWL R DL (e.g., unions, >>> and existential and universal restrictions may only occur on one >>> side of subclass axioms, respectively). Isn't this alone already >>> "counter-intuitive", at least to people who do not understand the >>> theoretic background behind this language? In comparison to this, >>> the OWL R Full ruleset looks pretty coherent to me. >> >> Only by deception. You allow the syntactic freedom without the >> semantics. That's not coherent, that's *bad*. >> >> At least by highlighting the asymmetries, you clearly indicate >> where what you say *has no effect*. >> >>> Well, so we have claims about "counter-intuitive" reasoning >>> results on both sides. I would call that a draw! :) >> >> I wouldn't. We don't have mere claims. >> >> [snip] >>> The point is that it would really not be a great marketing >>> statement to say: "We have a sound OWL RL reasoner!". >> >> I don't see how you can simultaneously claim that users won't care >> about silent no-semantics axioms and yet care about calling it >> sound. Calling the rules complete for all graphs is *just* >> marketing and *bad* marketing because it relies on some fairly >> unpretty sophistry. >> >>> Building sound-only reasoners is a trivial task (just take a "zero- >>> reasoner", which does not produce any inferences). >> >> Oh man, you're clearly not in marketing land now. >> >>> And a reasoner, which just implements the "official OWL R >>> ruleset", wouldn't be more than just an OWL R sound-only reasoner. >>> While there would be other reasoners around, which would really be >>> sound and complete w.r.t. the OWL R semantics. Would anyone buy >>> the former reasoner under these circumstances? >> >> Sure, for scalability, for brand name, because they don't care >> about completeness, or for any of a number of reasons. >> >> (BTW, in bioinformatics circles, soundness is *much* less >> interesting than completeness (assuming it's not overnoised). >> Talking with folks like Robert Stevens, I find that they would be >> *much* more perturbed by constructs that *didn't* have effects >> though they look like they should. I *imagine* HCLS is a field that >> would be highly interested in OWL-R (as a compilation target, and >> directly)). >> >> I think it's a *very* bad idea to get too creative in profile land, >> in the standard. I'm not saying it's exactly analogous, but OWL >> Lite should be a cautionary tale. >> >> Cheers, >> Bijan. >> > > "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 > > > > > "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 12:19:45 UTC