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- Doherty, Patrick, 1957-, et al.
(författare)
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Circumscribing features and fluents
- 1994
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Ingår i: Temporal Logic. - Berlin/New York : Springer Berlin/Heidelberg. - 354058241X - 038758241X ; , s. 82-100
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Bokkapitel (refereegranskat)abstract
- Sandewall has recently proposed a systematic approach to the representation of knowledge about dynamical systems that includes a general framework in which to assess the range of applicability of existing and new logics for action and change and to provide a means of studying whether and in what sense the logics of action and change are relevant for intelligent agents. As part of the framework, a number of logics of preferential entailment are introduced and assessed for particular classes of action scenario descriptions. This paper provides syntactic characterizations of several of these relations of preferential entailment in terms of standard FOPC and circumscription axioms. The intent is to simplify the process of comparison with existing formalisms which use more traditional techniques and to provide a basis for studying the feasibility of compiling particular classes of problems into logic programs.
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| 3. |
- Doherty, Patrick, 1957-, et al.
(författare)
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Computing circumscription revisited : A reduction algorithm.
- 1994
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, a great deal of attention has been devoted to logics of "commonsense" reasoning. Among the candidates proposed, circumscription has been perceived as an elegant mathematical technique for modeling nonmonotonic reasoning, but difficult to apply in practice. The major reason for this is the nd-order nature of circumscription axioms and the difficulty in finding proper substitutions of predicate expressions for predicate variables. One solution to this problem is to compile, where possible, nd-order formulas into equivalent 1st-order formulas. Although some progress has been made using this approach, the results are not as strong as one might desire and they are isolated in nature. In this article, we provide a general method which can be used in an algorithmic manner to reduce circumscription axioms to 1st-order formulas. The algorithm takes as input an arbitrary 2nd-order formula and either returns as output an equivalent 1st-order formula, or terminates with failure. The class of 2nd-order formulas, and analogously the class of circumscriptive theories which can be reduced, provably subsumes those covered by existing results. We demonstrate the generality of the algorithm using circumscriptive theories with mixed quantifiers (some involving Skolemization), variable constants, non-separated formulas, and formulas with n-ary predicate variables. In addition, we analyze the strength of the algorithm and compare it with existing approaches providing formal subsumption results.
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| 4. |
- Doherty, Patrick, 1957-, et al.
(författare)
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Defaults as first-class citizens
- 1992
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Ingår i: Proceedings of the 22nd International Symposium on Multiple-Valued Logic (SMVL). - : IEEE Computer Society. - 0818626801 ; , s. 146-154
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Konferensbidrag (refereegranskat)abstract
- A nonmonotonic logic with explicit defaults, NML3, is presented. It is characterized by the following features: (1) the use of the strong Kleene three-valued logic as a basis; (2) the addition of an explicit default operator which enables distinguishing tentative conclusions from ordinary conclusions in the object language; and (3) the use of the idea of preferential entailment to generate nonmonotonic behavior. The central feature of the formalism, the use of an explicit default operator with a model-theoretic semantics based on the notion of a partial interpretation, distinguishes NML3 from most previous formalisms. By capitalizing on the distinction between tentative and ordinary conclusions, NML3 provides increased expressibility in comparison to many of the standard nonmonotonic formalisms and greater flexibility in the representation of subtle aspects of default reasoning. This is shown through examples.
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| 5. |
- Doherty, Patrick, 1957-, et al.
(författare)
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Distinguishing between facts and default assumptions.
- 1992
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Ingår i: Non-Monotonic Reasoning and Partial Semantics. Ellis Horwood Workshops.. - New York : Ellis Horwood Ltd.. - 0136251463 - 9780136251460
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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