Proof complexity of propositional default logic

  • Authors:
  • Olaf Beyersdorff;Arne Meier;Sebastian Müller;Michael Thomas;Heribert Vollmer

  • Affiliations:
  • Institute of Theoretical Computer Science, Leibniz University Hanover, Hanover, Germany;Institute of Theoretical Computer Science, Leibniz University Hanover, Hanover, Germany;Faculty of Mathematics and Physics, Charles University Prague, Prague, Czech Republic;Institute of Theoretical Computer Science, Leibniz University Hanover, Hanover, Germany;Institute of Theoretical Computer Science, Leibniz University Hanover, Hanover, Germany

  • Venue:
  • Archive for Mathematical Logic
  • Year:
  • 2011

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Abstract

Default logic is one of the most popular and successful formalisms for non-monotonic reasoning. In 2002, Bonatti and Olivetti introduced several sequent calculi for credulous and skeptical reasoning in propositional default logic. In this paper we examine these calculi from a proof-complexity perspective. In particular, we show that the calculus for credulous reasoning obeys almost the same bounds on the proof size as Gentzen's system LK. Hence proving lower bounds for credulous reasoning will be as hard as proving lower bounds for LK. On the other hand, we show an exponential lower bound to the proof size in Bonatti and Olivetti's enhanced calculus for skeptical default reasoning.