Revising Nonmonotonic Theories: The Case of Defeasible Logic

Abstract. The revision and transformation of knowledge is widely recognized as a key issue in knowledge representation and reasoning. Reasons for the importance of this topic are the fact that intelligent systems are gradually developed and re ned, and that often the environment of an intelligent system is not static but changes over time. Traditionally belief revision has been concerned with revising rst order theories. Nonmonotonic reasoning provides rigorous techniques for reasoning with incomplete information. Until recently the dynamics of nonmonotonic reasoning approaches has attracted little attention. This paper studies the dynamics of defeasible logic, a simple and e cient form of nonmonotonic reasoning based on defeasible rules and priorities. We de ne revision and contraction operators and propose postulates. Our postulates try to follow the ideas of AGM belief revision as far as possible, but some AGM postulates clearly contradict the nonmonotonic nature of defeasible logic...

• Type: Conference
• Year: 1999
• Where: KI
• Authors: David Billington, Grigoris Antoniou, Guido Governatori, Michael J. Maher
• Keywords: Artificial Intelligence, Belief Revision, KI 1999, Nonmonotonic Reasoning, Nonmonotonic Reasoning Approaches