Matrix Interpretations for Proving Termination of Term Rewriting

  • Authors:
  • Jörg Endrullis;Johannes Waldmann;Hans Zantema

  • Affiliations:
  • Department of Computer Science, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands 1081 HV;Hochschule für Technik, Wirtschaft und Kultur (FH) Leipzig, Leipzig, Germany 04251;Department of Computer Science, Technische Universiteit Eindhoven, Eindhoven, The Netherlands 5600 MB

  • Venue:
  • Journal of Automated Reasoning
  • Year:
  • 2008

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Abstract

We present a new method for automatically proving termination of term rewriting. It is based on the well-known idea of interpretation of terms where every rewrite step causes a decrease, but instead of the usual natural numbers we use vectors of natural numbers, ordered by a particular nontotal well-founded ordering. Function symbols are interpreted by linear mappings represented by matrices. This method allows us to prove termination and relative termination. A modification of the latter, in which strict steps are only allowed at the top, turns out to be helpful in combination with the dependency pair transformation. By bounding the dimension and the matrix coefficients, the search problem becomes finite. Our implementation transforms it to a Boolean satisfiability problem (SAT), to be solved by a state-of-the-art SAT solver.