A decomposition method for CNF minimality proofs

  • Authors:
  • Endre Boros;Ondřej Epek;Petr Kučera

  • Affiliations:
  • RUTCOR, Rutgers University, P.O. Box 5062, New Brunswick, NJ 08903, USA;Department of Theoretical Computer Science and Mathematical Logic, Faculty of Mathematics and Physics, Charles University in Prague, Malostranské nám. 25, 118 00 Praha 1, Czech Republic;Department of Theoretical Computer Science and Mathematical Logic, Faculty of Mathematics and Physics, Charles University in Prague, Malostranské nám. 25, 118 00 Praha 1, Czech Republic

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2013

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Abstract

A CNF is minimal if no shorter CNF representing the same function exists, where by CNF length we mean either the number of clauses or the total number of literals (sum of clause lengths). In this paper we develop a decomposition approach that can be in certain situations applied to a CNF formula when proving its minimality. We give two examples in which this decomposition approach is used. Both examples deal with pure Horn minimization, a problem defined as follows: given a pure Horn CNF, construct a logically equivalent pure Horn CNF which is the shortest possible (either w.r.t. the number of clauses or w.r.t. the total number of literals). Both presented examples give alternative proofs of known complexity results for pure Horn minimization.