Annals of Mathematics and Artificial Intelligence

, Volume 15, Issue 1, pp 61–82

Another perspective on default reasoning

  • Daniel Lehmann

DOI: 10.1007/BF01535841

Cite this article as:
Lehmann, D. Ann Math Artif Intell (1995) 15: 61. doi:10.1007/BF01535841


The lexicographic closure of any given finite setD of normal defaults is defined. A conditional assertiona ❘∼b is in this lexicographic closure if, given the defaultsD and the facta, one would concludeb. The lexicographic closure is essentially a rational extension ofD, and of its rational closure, defined in a previous paper. It provides a logic of normal defaults that is different from the one proposed by R. Reiter and that is rich enough not to require the consideration of non-normal defaults. A large number of examples are provided to show that the lexicographic closure corresponds to the basic intuitions behind Reiter's logic of defaults.

Copyright information

© J.C. Baltzer AG, Science Publishers 1995

Authors and Affiliations

  • Daniel Lehmann
    • 1
  1. 1.Institute of Computer ScienceHebrew UniversityJerusalemIsrael