A coherence-based approach to default reasoning

  • Salem Benferhat
  • Laurent Garcia
Invited Papers
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1244)


In the last 15 years, several default reasoning systems have been proposed to deal with rules having exceptions. Each of these systems has been shown to be either cautious (where some intuitive conclusions do not follow from the default base), or adventurous (some debatable conclusions are inferred). However, the cautiousness and the adventurous aspect of these systems are often due to the incomplete way of describing our knowledge, and that plausible conclusions depend on the meaning (semantics) assigned to propositional symbols. This paper mainly contains two parts. The first part discusses, with simple default bases (where the used symbols have no a priori meaning), which assumptions are assumed when a given conclusion is considered as intuitive. The second part investigates a local approach to deal with default rules of the form “generally, if α then β” having possibly some exceptions. The idea is that when a conflict appears (due to observing exceptional situations), we first localize the sets of pieces of information which are responsible for conflicts. Next, using a new definition of specificity, we attach priorities to default rules inside each conflict. Lastly, three proposals are made to solve conflicts and restore the consistency of the knowledge base. A comparative study with some existing systems is given.


Default Rule Nonmonotonic Reasoning Default Reasoning Intuitive Conclusion Debatable Conclusion 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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  1. S. Benferhat, C. Cayrol, D. Dubois, J. Lang & H. Prade (1993). Inconsistency management and prioritized syntax-based entailment. Proc. of the 13th Intern. Joint Conf. on A. I. (IJCAI'93). 640–645.Google Scholar
  2. S. Benferhat, D. Dubois & H. Prade (1994). Expressing Independence in a Possibilistic Framework and its Application to Default Reasoning. Proc. of the 11th European Conf. on A. I. (ECAI'94). 150–154.Google Scholar
  3. S. Benferhat, A. Saffiotti & P. Smets (1995) Belief functions and default reasoning. Proc. of the 11th conf. on Uncertainty in Artificial Intelligence (UAI'95). 19–26.Google Scholar
  4. C. Boutilier (1992). What is a Default priority?. Proc. of the 9th Canadian Conf. on Artificial Intelligence (AI'92). 140–147.Google Scholar
  5. G. Brewka (1989). Preferred subtheories: an extended logical framework for default reasoning. Proc. of the 11th Intern. Joint Conf. on A. I. (IJCAI'89). 1043–1048.Google Scholar
  6. J. P. Delgrande & T. H. Schaub (1994). A general approach to specificity in default reasoning. Proc. of the 4th Intern. Conf. on Princ. of Knowledge Representation and Reasoning (KR'94). 146–157.Google Scholar
  7. D. Dubois, J. Lang & H. Prade (1994). Possibilistic logic. In: Handbook of Logic in A. I. and Logic Programming, vol. 3. Oxford University Press. 439–513.Google Scholar
  8. P.M. Dung (1993). On the acceptability of arguments and its fundamental role in nonmonotonic reasoning and logic programming. Proc. of the 13th Intern. Joint Conf. on A. I. (IJCAI'93). 852–857.Google Scholar
  9. D. Gabbay (1985). Theoretical foundations for non-monotonic reasoning in expert systems. In: Logics and models of Concurrent Systems. Springer Verlag. Berlin. 439–457.Google Scholar
  10. P. Gärdenfors & D. Makinson (1994). Nonmonotonic inference based on expectations. In: Artificial Intelligence, 65. 197–245.Google Scholar
  11. H. Geffner (1992). Default reasoning: causal and conditional theories. MIT Press.Google Scholar
  12. S. Kraus, D. Lehmann & M. Magidor (1990). Nonmonotonic reasoning, preferential models and cumulative logics. In: Artificial Intelligence, 44. 167–207.Google Scholar
  13. D. Lehmann (1993). Another perspective on default reasoning. Technical report. Hebrew University, Jerusalem.Google Scholar
  14. D. Lehmann & M. Magidor (1992). What does a conditional knowledge base entail? Artificial Intelligence, 55. 1–60.Google Scholar
  15. Y. Moinard (1987). Donner la préférence au défaut le plus spécifique. Actes du 6éme congrés AFCET-RFIA. 1123–1132.Google Scholar
  16. J. Pearl (1990). System Z: A natural ordering of defaults with tractable applications to default reasoning. Proc. of the 3rd Conf. on Theoretical Aspects of Reasoning about Knowledge (TARK'90). 121–135.Google Scholar
  17. R. Reiter (1980). A logic for default reasoning. In: Artificial Intelligence, 13. 81–132.Google Scholar
  18. R. Reiter & Criscuolo (1981). On interacting defaults. Proc. of the 7th Intern. Joint Conf. on A. I. (IJCAI'81). 270–276.Google Scholar
  19. G. R. Simari & R. P. Loui (1992). A mathematical treatment of defeasible reasoning and its implementation. Artificial Intelligence, 53. 125–157.Google Scholar
  20. D. S. Touretzky (1984). Implicit ordering of defaults in inheritance systems. Proc. of the 1984 National Conf. on A. I. (AAAI'84). 322–325.Google Scholar
  21. M. A. Williams (1996). Towards a Practical Approach to Belief Revision: Reason-Based Change. Proc. of the 5th Intern. Conf. on Princ. of Knowledge Representation and Reasoning (KR'96).Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • Salem Benferhat
    • 1
  • Laurent Garcia
    • 1
  1. 1.IRITCNRS-Université Paul SabatierToulouse CedexFrance

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