PSPACE bounds for rank-1 modal logics

  • Authors:
  • LUTZ Schröder;Dirk Pattinson

  • Affiliations:
  • DFKI Bremen and Universität Bremen, Bremen, Germany;Imperial College London, London, UK

  • Venue:
  • ACM Transactions on Computational Logic (TOCL)
  • Year:
  • 2009

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Abstract

For lack of general algorithmic methods that apply to wide classes of logics, establishing a complexity bound for a given modal logic is often a laborious task. The present work is a step towards a general theory of the complexity of modal logics. Our main result is that all rank-1 logics enjoy a shallow model property and thus are, under mild assumptions on the format of their axiomatisation, in PSPACE. This leads to a unified derivation of tight PSPACE-bounds for a number of logics, including K, KD, coalition logic, graded modal logic, majority logic, and probabilistic modal logic. Our generic algorithm moreover finds tableau proofs that witness pleasant proof-theoretic properties including a weak subformula property. This generality is made possible by a coalgebraic semantics, which conveniently abstracts from the details of a given model class and thus allows covering a broad range of logics in a uniform way.