Consequence finding and computing answers with defaults

  • Authors:

  • Katsumi Inoue;Koji Iwanuma;Hidetomo Nabeshima

  • Affiliations:

  • National Institute of Informatics, Tokyo, Japan 101-8430;Department of Computer and Media Engineering, Yamanashi University, Kofu, Japan 400-8511;Department of Computer and Media Engineering, Yamanashi University, Kofu, Japan 400-8511

  • Venue:
  • Journal of Intelligent Information Systems
  • Year:
  • 2006

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Abstract

Consequence finding has been recognized as an important technique in many intelligent systems involving inference. In previous work, propositional or first-order clausal theories have been considered for consequence finding. In this paper, we consider consequence finding from a default theory, which consists of a first-order clausal theory and a set of normal defaults. In an extension of a default theory, consequence finding can be done with the generating defaults for the extension. Alternatively, all extensions can be represented at once with the conditional answer format, which represents how a conclusion depends on which defaults.We also propose a procedure for consequence finding and query answering in a default theory using the first-order consequence-finding procedure SOL. In computing consequences from default theories efficiently, the notion of TCS-freeness is most important to prune a large number of irrational tableaux induced by the generating defaults for an extension. In order to simulate the TCS-freeness, the refined SOL calculus called SOL-S(驴) is adopted using skip preference and complement checking.