From: patrick hayes (phayes@ai.uwf.edu)
Date: 06/10/02
>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 -- --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola, FL 32501 (850)202 4440 fax phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
This archive was generated by hypermail 2.1.4 : 06/10/02 EDT