armin@ai.toronto.edu (Armin Haken) (02/29/88)
On Tuesday March 1 at 2PM in room SF1105, Prof. Daniel Lehmann from
the Hebrew University will give an AI seminar. The abstract follows.
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Non monotonic logics: models and proofs
Prof. Daniel Lehmann, Dept. of Computer Science,
Hebrew University, Jerusalem 91904 ISRAEL.
Abstract:
A general framework for the study of non monotonic logics is proposed.
It focuses (as proposed by Dov Gabbay) on the notion of a
non monotonic deduction and the derivability of such deductions from others.
Inference rules that should hold in all non monotonic logics are described
(essentially those of Gabbay); additional rules are discussed. A set
of non monotonic deductions provides a general knowledge base from which one,
on the basis of specific information about the world, may draw probable
conclusions by use of the inference rules. The main point of this paper is
the definition of the semantics of non monotonic deduction. The semantics
are defined using possible worlds models in which some worlds are more
natural than others. A soundness and completeness proof shows
that the models match exactly the inference rules proposed. This should be
considered a step towards the general study and the classification of the
different non monotonic logics. This paper is restricted to propositional
logics.
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