Practical Handling of Exception-Tainted Rules and Independence Information in Possibilistic Logic

  • Authors:

  • Salem Benferhat;Didier Dubois;Henri Prade

  • Affiliations:

  • Institut de Recherche en Informatique de Toulouse (I.R.I.T.), Université Paul Sabatier, C.N.R.S., 118 route de Narbonne, 31062 Toulouse Cedex 4, France. E-mail: Benferha@irit.fr, Dubo ...;Institut de Recherche en Informatique de Toulouse (I.R.I.T.), Université Paul Sabatier, C.N.R.S., 118 route de Narbonne, 31062 Toulouse Cedex 4, France. E-mail: Benferha@irit.fr, Dubo ...;Institut de Recherche en Informatique de Toulouse (I.R.I.T.), Université Paul Sabatier, C.N.R.S., 118 route de Narbonne, 31062 Toulouse Cedex 4, France. E-mail: Benferha@irit.fr, Dubo ...

  • Venue:
  • Applied Intelligence
  • Year:
  • 1998

Quantified Score

Hi-index 0.00

Visualization

Abstract

This paper provides a survey of possibilistic logic as a simple andefficient tool for handling nonmonotonic reasoning, with some emphasis onalgorithmic issues. In our previous works, two well-known nonmonotonic systems have been encoded in the possibility theory framework: the preferential inference based on System P, and the rational closure inference proposed by Lehmann and Magidor which relies on System P augmented with a rational monotony postulate. System P is known to providereasonable but very cautious conclusions, and in particular, preferentialinference is blocked by the presence of “irrelevant” properties. When using Lehmann‘s rational closure, the inference machinery, which is then more productive, may still remain too cautious, or on the contrary, provide counter -intuitive conclusions. The paper proposes an approach to overcome the cautiousness of System P and the problems encountered by the rational closure inference. This approach takes advantage of (contextual) independence assumptions of the form: the fact that γ is true (or is false) does not affect the validity of the rule“normally if α then β”. The modelling of suchindependence assumptions is discussed in the possibilistic framework.Moreover, we show that when a counter-intuitive conclusion of a set ofdefaults can be inferred, it is always possible to repair the set ofdefaults by adding suitable information so as to produce the desiredconclusions and block unsuitable ones.