Dual-normal logic programs-The forgotten class

Johannes K. Fichte, MirosŁaw Truszczyński, Stefan Woltran

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Disjunctive Answer Set Programming is a powerful declarative programming paradigm with complexity beyond NP. Identifying classes of programs for which the consistency problem is in NP is of interest from the theoretical standpoint and can potentially lead to improvements in the design of answer set programming solvers. One of such classes consists of dual-normal programs, where the number of positive body atoms in proper rules is at most one. Unlike other classes of programs, dual-normal programs have received little attention so far. In this paper we study this class. We relate dual-normal programs to propositional theories and to normal programs by presenting several inter-translations. With the translation from dual-normal to normal programs at hand, we introduce the novel class of body-cycle free programs, which are in many respects dual to head-cycle free programs. We establish the expressive power of dual-normal programs in terms of SE-and UE-models, and compare them to normal programs. We also discuss the complexity of deciding whether dual-normal programs are strongly and uniformly equivalent.

Original languageEnglish
Pages (from-to)495-510
Number of pages16
JournalTheory and Practice of Logic Programming
Issue number4-5
StatePublished - Sep 3 2015

Bibliographical note

Publisher Copyright:
© 2015 Cambridge University Press.


  • answer set programming
  • classes of logic programs
  • propositional satisfiability
  • strong and uniform equivalence

ASJC Scopus subject areas

  • Software
  • Artificial Intelligence
  • Theoretical Computer Science
  • Hardware and Architecture
  • Computational Theory and Mathematics


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