On Acyclic and Head-Cycle Free Nested Logic Programs

  • Thomas Linke
  • Hans Tompits
  • Stefan Woltran
Part of the Lecture Notes in Computer Science book series (LNCS, volume 3132)


We define the class of head-cycle free nested logic programs, and its proper subclass of acyclic nested programs, generalising similar classes originally defined for disjunctive logic programs. We then extend several results known for acyclic and head-cycle free disjunctive programs under the stable-model semantics to the nested case. Most notably, we provide a propositional semantics for the program classes under consideration. This generalises different extensions of Fages’ theorem, including a recent result by Erdem and Lifschitz for tight logic programs. We further show that, based on a shifting method, head-cycle free nested programs can be rewritten into normal programs in polynomial time and space, extending a similar technique for head-cycle free disjunctive programs. All this shows that head-cycle free nested programs constitute a subclass of nested programs possessing a lower computational complexity than arbitrary nested programs, providing the polynomial hierarchy does not collapse.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2004

Authors and Affiliations

  • Thomas Linke
    • 1
  • Hans Tompits
    • 2
  • Stefan Woltran
    • 2
  1. 1.Institut für InformatikUniversität PotsdamPotsdamGermany
  2. 2.Institut für Informationssysteme 184/3Technische Universität WienViennaAustria

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