From: Pat Hayes (phayes@ai.uwf.edu)
Date: 10/25/01
I think talking about skolems is a red herring. If the KB has skolems in it, then as far as the QE is concerned they are just functions; their status as skolems is invisible. And as far as generating skolems during the query process, that is simply invalid, and shouldn't be allowed to happen. The only logical distinctions we need to draw are between terms that can have values bound to them in the query-answering process (universals in the KB and existentials in the query, speaking purely logically) and those that cannot (all constants and names; existentials in the KB and universals in the query), and which of the former are considered to be the answer-binding-places (a subset of the existentials in the query, usually.) The only real complication over logical QA is that in our case the KB and the QE have disjoint scopes, and it is never valid to take an existential variable name outside its scope. The querying process basically hands the query to the KB and says: prove this. That puts the query temporarily inside the KB's scope, but if a query variable gets bound to an existential in the KB, then it must not hand that binding back to the QE; hence the <blank> complication. (This isn't just post-processing stuff: it would be logically invalid to do that. ) Notice that handing back <blank> is not handing back a skolem. Its like saying 'a frog' without calling it Fred. (You could say that it is a kind of licence to the QE to create its own skolem, but that would be misleading. Such name creation would be independent of the query-answering. If an reasoning engine wants to create names for things, it can do that; but that's its private business, not something that arises from a transaction with another agent.) 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
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