A PSpace Algorithm for Graded Modal Logic

  • Authors:
  • Stephan Tobies

  • Affiliations:
  • -

  • Venue:
  • CADE-16 Proceedings of the 16th International Conference on Automated Deduction: Automated Deduction
  • Year:
  • 1999

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Abstract

We present a PSpace algorithm that decides satisfiability of the graded modal logic Gr(KR)--a natural extension of propositional modal logic KR by counting expressions--which plays an important role in the area of knowledge representation. The algorithm employs a tableaux approach and is the first known algorithm which meets the lower bound for the complexity of the problem. Thus, we exactly fix the complexity of the problem and refute a EXPTIME-hardness conjecture. This establishes a kind of "theoretical benchmark" that all algorithmic approaches can be measured with.