New Generation Computing

, Volume 9, Issue 3, pp 387–400

Logic programs with exceptions

  • Robert A. Kowalski
  • Fariba Sadri
Special Issue

DOI: 10.1007/BF03037170

Cite this article as:
Kowalski, R.A. & Sadri, F. New Gener Comput (1991) 9: 387. doi:10.1007/BF03037170


We extend logic programming to deal with default reasoning by allowing the explicit representation of exceptions in addition to general rules. To formalise this extension, we modify the answer set semantics of Gelfond and Lifschitz, which allows both classical negation and negation as failure.

We also propose a transformation which eliminates exceptions by using negation by failure. The transformed program can be implemented by standard logic programming methods, such as SLDNF. The explicit representation of rules and exceptions has the virtue of greater naturalness of expression. The transformed program, however, is easier to implement.


Logic Programs Rules and Exceptions Default Reasoning Answer Set Semantics e-answer Set Semantics 

Copyright information

© Ohmsha, Ltd. and Springer 1991

Authors and Affiliations

  • Robert A. Kowalski
    • 1
  • Fariba Sadri
    • 1
  1. 1.Department of ComputingImperial CollegeLondonU. K.

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