On Skolemization And Proof Complexity

  • Authors:
  • Matthias Baaz;Alexander Leitsch

  • Affiliations:
  • Institut für Algebra und Diskrete Mathematik, Technische Universität Wien, Wiedner Hauptstraβe 8-10, A-1040 Wien, Austria;Institut für Computersprachen, Technische Universität Wien, Resselgasse 3, A-1040 Wien, Austria, email, leitsch@csdecl.twwien.ac.at

  • Venue:
  • Fundamenta Informaticae
  • Year:
  • 1994

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Abstract

The impact of Skolemization on the complexity of proofs in the sequent calculus is investigated. It is shown that prefix Skolemization may result in a nonelementary increase of Herbrand complexity (i. e. the minimal number of constituents in a Herbrand disjunction) versus structural Skolemization. Moreover it is shown that restricting the range of quantifiers never increases Herbrand complexity. The results provide a general mathematical justification for minimizing the range of quantifiers (by means of shifting) before Skolemization of formulas.