Revising Nonmonotonic Theories: The Case of Defeasible Logic

D. Billington, G. Antoniou, G. Governatori, M. Maher

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

20 Citations (Scopus)


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 refined, and that often the environment of an intelligent system is not static but changes over time. Traditionally belief revision has been concerned with revising first 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 efficient form of nonmonotonic reasoning based on defeasible rules and priorities. We define 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, as we explain. Finally we verify that the operators satisfy the postulates.

Original languageEnglish
Title of host publicationKI-1999
Subtitle of host publicationAdvances in Artificial Intelligence - 23rd Annual German Conference on Artificial Intelligence Bonn, Germany, September 13–15, 1999 Proceedings
EditorsWolfram Burgard, Armin B. Cremers, Thomas Cristaller
Place of PublicationBerlin
PublisherSpringer Verlag
Number of pages12
VolumeLNCS/LNAI 1701
ISBN (Electronic)9783540482383
ISBN (Print)3540664955, 9783540664956
Publication statusPublished - 1 Sep 1999
Externally publishedYes
Event23rd Annual German Conference on Artificial Intelligence - Bonn, Germany
Duration: 13 Sep 199915 Sep 1999
Conference number: 23

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
PublisherSpringer Verlag
Volume1701 LNCS/LNAI
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference23rd Annual German Conference on Artificial Intelligence
Abbreviated titleKI 1999


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