- From: Dan Connolly <connolly@w3.org>
- Date: 05 Apr 2002 08:08:54 -0600
- To: Ian Horrocks <horrocks@cs.man.ac.uk>
- Cc: Libby Miller <Libby.Miller@bristol.ac.uk>, "Peter F. "Patel-Schneider <pfps@research.bell-labs.com>, webont <www-webont-wg@w3.org>
On Fri, 2002-04-05 at 07:08, Ian Horrocks wrote: > On March 21, Dan Connolly writes: > > On Thu, 2002-03-21 at 14:28, Ian Horrocks wrote: > > > On March 21, Libby Miller writes: > > > > > > > > > > As noted in the design discussions for DAML+OIL, I don't > > > > > see sufficient justification for making V disjoint > > > > > from R. > > > > > > > > > > It seems silly not to be able to talk about the intersection > > > > > of two sets of strings, or UniqueProperty's whose > > > > > range is dates, or whatever. > > > > > > This means that any OWL reasoner has to take on responsibility for > > > reasoning about types > > > > I gather when you say "OWL reasoner" you mean a complete > > reasoner. > > > > I'm not very interested in such a thing. > > > > Regular old horn-clause/datalog reasoners > > (with some built-in predicates like > > string:lessThan and such) seem > > to get me what I need pretty well. > > Dan, > > It seems that, on the basis of a few toy examples where using ad-hoc > reasoning seems give the results you want/expect, you conclude that > this will be appropriate/adequate for all applications. No, just for an interesting class of applications. By the way, if you consider formalizing the operations of W3C[1] to be a toy example, I'm interested to know what sort of applications you would take seriously. > I don't find > this argument very convincing. As I say, I didn't make that argument. I'm arguing that we can advance the state of the art without a completeness requirement. > Even w.r.t. ontology level reasoning I expect things to rapidly get > large and complex enough that humans wont be able to check all > inferences - we will just have to trust that the reasoner got it > right. Soundness is therefore essential, and completeness highly > desirable. Yes, soundness is essential. I don't see why completeness is all that interesting in the general case. I expect various reasoners to be complete for various classes of problems. > For example, when multiple processes are interacting, some > action may be taken by one process on the basis of a non-inference by > another process, That's non-monotonic reasoning. Part of life in the semantic web is: don't do that (without explicit license). > so incompleteness can easily lead to "unsoundness". Unsoundness can result from all sorts of bugs; this is just one of them. Actually, unsound/heuristic reasoning can be pretty interesting, as long as it's not confused with formal reasoning; e.g. I conclude based on your recent buying patterns that the following products are likely to be interesting to you: X, Y, Z. I didn't arrive at this conclusion based on sound reasoning, so take the recommendations with a grain of salt. or I conclude, based on a search of my extensive holdings, that there are no court cases in that jurisdiction involving chimpanzees and volkswagens. Digitally signed, The BigLaw online service. > As far as the disjointness of object/data domains and properties is > concerned, there are also good pragmatic reasons for this, including > the ability to use hybrid designs for OWL reasoners, i.e., the ability > for an owl "object class" reasoner implementation to "bolt on" a type > checker for arbitrary type systems. That seems like an interesting software architecture for a certain class of problems. But why should it constrain the language we're designing? If such a system came across some data where "3" was a member of a class, I'd expect it to throw an exception ala: Sorry, this software is limited to problems where the datatypes and the class members are disjoint. I can't compute the answer you asked for. not Sorry, your data doesn't conform to the language specification. [1] e.g. we're formalizing our tech report digital library, and the workflow around it. http://www.w3.org/2002/01/tr-automation/ -- Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Friday, 5 April 2002 09:08:41 UTC