Structuring Resolution Proofs by Introducing New Lemmata

  • Authors:
  • K. Hörwein

  • Affiliations:
  • Abteilung für Anwendungen der formalen Logik, Institut für Computersprachen, Technische Universität Wien, Karlsplatz 13/E185-2, A-1040 Wien, Austria. e-mail: karin@logic.tuwien.ac.a ...

  • Venue:
  • Journal of Automated Reasoning
  • Year:
  • 1997

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Abstract

Resolution proofs are unstructured by their very nature, since theycannot use substantial lemmata. To impose structure on given resolutionproofs and thereby improve their readability we will introduce new lemmatain a postprocessing step. As these lemmata cannot be generated byresolution, we will employ function introduction rules as presented by Baazand Leitsch and give a correct and complete criterion for theirapplicability to the proofs. Applying function introduction rules toresolution proofs enables us to detect and eliminate certain homomorphicsubproofs immune to the known redundancy elimination rules. For the caseswhen the criterion is satisfied we will characterize the transformation oftree resolution proofs to their condensation-reduced functional extensions,which may result in a double exponential reduction of proof height.Moreover, the proofs obtained by this transformation are more structured andhence more intelligible.