Abstract
We formulate a narrowing-based decision procedure for E-unifiability. Termination is obtained requiring a narrowing bound: a bound on the length of narrowing sequences. We study general conditions under which the method guarantees that E-unifiability is in NP. The procedure is also extended to narrowing modulo AC (associativity and commutativity). As an application of our method, we prove NP-completeness of unifiability modulo bisimulation in process algebra with proper iteration, significantly extending a result in [8]. We also give (new) proofs, under a unified point of view, of NP-decidability of I, ACI, ACI1-unifiability and of unifiability in quasi-groups and central groupoids.
Work carried out within the MURST project TOSCA (Theory of concurrency, higher order and types)
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Viola, E. (2001). E-unifiability via Narrowing. In: Theoretical Computer Science. ICTCS 2001. Lecture Notes in Computer Science, vol 2202. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-45446-2_27
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DOI: https://doi.org/10.1007/3-540-45446-2_27
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