Alternating Fixpoint Theory for Logic Programs with Priority

  • Kewen Wang
  • Lizhu Zhou
  • Fangzhen Lin
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1861)


van Gelder’s alternating fixpoint theory has proven to be a very useful tool for unifying and characterizing various semantics for logic programs without priority. In this paper we propose an extension of van Gelder’s alternating fixpoint theory and show that it can be used as a general semantic framework for logic programs with priority. Specifically, we define three declarative and model-theoretic semantics in this framework for prioritied logic programs: prioritized answer sets, prioritized regular extensions and prioritized well-founded model. We show that all of these semantics are natural generalizations of the corresponding semantics for logic programs without priority. We also show that these semantics have some other desirable properties. In particular, they can handle conflicts caused indirectly by the priorities.


Logic programs alternating fixpoints priority answer sets well-founded model 


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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • Kewen Wang
    • 1
  • Lizhu Zhou
    • 1
  • Fangzhen Lin
    • 2
  1. 1.Department of Computer Science and TechnologyTsinghua UniversityBeijingChina
  2. 2.Department of Computer ScienceHong Kong University of Science and TechnologyKowloonHong Kong

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