Match-Bounded String Rewriting Systems

  • Authors:

  • Alfons Geser;Dieter Hofbauer;Johannes Waldmann

  • Affiliations:

  • National Institute of Aerospace, 144 Research Drive, 23666, Hampton, VA, USA; , Mühlengasse 16, 34125, Kassel, VA, Germany;Wirtschaft und Kultur (FH) Leipzig, Fb IMN, Hochschule für Technik, PF 30 11 66, Mühlengasse 16, 04251, Leipzig, VA, Germany

  • Venue:
  • Applicable Algebra in Engineering, Communication and Computing
  • Year:
  • 2004

Quantified Score

Hi-index 0.00

Visualization

Abstract

We introduce a new class of automated proof methods for the termination of rewriting systems on strings. The basis of all these methods is to show that rewriting preserves regular languages. To this end, letters are annotated with natural numbers, called match heights. If the minimal height of all positions in a redex is h then every position in the reduct will get height h+1. In a match-bounded system, match heights are globally bounded. Using recent results on deleting systems, we prove that rewriting by a match-bounded system preserves regular languages. Hence it is decidable whether a given rewriting system has a given match bound. We also provide a criterion for the absence of a match-bound. It is still open whether match-boundedness is decidable. Match-boundedness for all strings can be used as an automated criterion for termination, for match-bounded systems are terminating. This criterion can be strengthened by requiring match-boundedness only for a restricted set of strings, namely the set of right hand sides of forward closures.