A CNF class generalizing exact linear formulas

  • Authors:
  • Stefan Porschen;Ewald Speckenmeyer

  • Affiliations:
  • Institut für Informatik, Universität zu Köln, Köln, Germany;Institut für Informatik, Universität zu Köln, Köln, Germany

  • Venue:
  • SAT'08 Proceedings of the 11th international conference on Theory and applications of satisfiability testing
  • Year:
  • 2008

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Abstract

The fibre view on clause sets, previously introduced in [12], is used in the present paper to define and investigate subclasses of CNF that appear to be polynomial time solvable w.r.t. SAT. The most interesting of these classes is a generalization of exact linear formulas, namely formulas such that each pair of distinct clauses has all variables in common or exactly one. By definition, in an exact linear formula each pair of distinct clauses has exactly one variable in common. SAT-solving for exact linear formulas was shown to be easy in [14]. Here we provide an algorithm solving the decision and counting variants of SAT for the generalized class in polynomial time. Moreover we study some other structurally defined formula classes on the basis of the fibre view. We show that these classes have the property that their members all are satisfiable or all are unsatisfiable.