NP-Completeness of Refutability by Literal-Once Resolution

  • Authors:
  • Stefan Szeider

  • Affiliations:
  • -

  • Venue:
  • IJCAR '01 Proceedings of the First International Joint Conference on Automated Reasoning
  • Year:
  • 2001

Quantified Score

Hi-index 0.00

Visualization

Abstract

A boolean formula in conjunctive normal form (CNF) F is refuted by literal-once resolution if the empty clause is inferred from F by resolving on each literal of F at most once. Literal-once resolution refutations can be found nondeterministically in polynomial time, though this restricted system is not complete. We show that despite of the weakness of literal-once resolution, the recognition of CNF-formulas which are refutable by literal-once resolution is NP-complete. We study the relationship between literal-once resolution and read-once resolution (introduced by Iwama and Miyano). Further we answer a question posed by Kullmann related to minimal unsatisfiability.