From: Dlmcg1@aol.com
Date: 06/11/02
I would also like to support the point that we should not attempt to require all answers implied by a kb. I would expect different reasoners to provide different reasoners and then some reasoners that attempt to be more "useful" to also be able to "defend" their answers. I would not specify the defense in our spec but I expect the defense to include things such as the ability to explain the reasoning that the reasoner used to generate an answer. A defense might also include information concerning the completeness of the reasoner and any attempt the reasoner may have made to generate a type of answer - possibly the most specific answer(s). deborah In a message dated 6/10/2002 11:25:06 AM Pacific Daylight Time, phayes@ai.uwf.edu writes: > >All this brings up the basic point: > > > > What is the definition of an answer? > > > >I don't think that this question has been satisfactorily answered. > > Indeed, and that may be the basic problem we are having here. Your > idea of answer apparently differs from Ian's, for example. > > My own view on this is that there is no *definition* of an answer, > but there are some conditions that all answers must satisfy. The only > condition that everyone will likely agree on is that any answer must > be entailed by the KB. (That is, that the instance of the query with > that binding is entailed by the KB.) I think in fact that this is > *all* that should be required in a spec., and that any attempt to > ensure that 'all' answers are given, or that logically equivalent KBs > must give identical answers, are misguided in the SW context; they > are far too strong to permit implementors to experiment, so will in > fact simply be ignored in practice; and in any case I do not think > that they are sensible in a Web open architecture. So I'm afraid that > I find this debate somewhat pointless and timewasting. > > Assuming that we do want to define something like the 'answer set' (I > would like to see some rational explanation for why this concept is > useful, by the way) , Ian has argued strongly that it should not > include all 'answers' that can be logically inferred from the KB, but > only those which arise from a binding of a query variable to a term > in the KB Herbrand universe, in order to keep the inferential burden > on the server within DL-manageable bounds. I am happy with that; but > given the resulting incompleteness, it seems silly to object to a > proposal on the grounds that logically equivalent KBs may not always > deliver the same answers. > > The point of the MID construction was to provide some useful > information to the querying system in the case where a binding itself > provides no useful information. We can debate the technical details > of how best to do this, but that some such mechanism is needed seems > to me to be obvious. In particular, any proposal for defining > 'answer' which arbitrarily forbids a server from transmitting useful > information to a querying engine, when it has already had to compute > that information in order to answer the query, seems to me to be so > mind-blowingly stupid as to not be worth discussing further. > > Pat > -- >
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