Termination of rewriting with right-flat rules

  • Authors:
  • Guillem Godoy;Eduard Huntingford;Ashish Tiwari

  • Affiliations:
  • Technical University of Catalonia, Barcelona, Spain;Technical University of Catalonia, Barcelona, Spain;SRI International, Menlo Park, CA

  • Venue:
  • RTA'07 Proceedings of the 18th international conference on Term rewriting and applications
  • Year:
  • 2007

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Abstract

Termination and innermost termination are shown to be decidable for term rewrite systems whose right-hand side terms are restricted to be shallow (variables occur at depth at most one) and linear. Innermost termination is also shown to be decidable for shallow rewrite systems. In all cases, we show that nontermination implies nontermination starting from flat terms. The proof is completed by using the useful enabling result that, for right shallow rewrite systems, existence of nonterminating derivations starting from a given term is decidable.We also show that termination is undecidable for shallow rewrite systems. For right-shallow systems, general and innermost termination are both undecidable.