Abstract
We consider equational unification and matching problems where the equational theory contains a nilpotent function, i.e., a function f satisfying f(x,x)=0 where 0 is a constant. Nilpotent matching and unification are shown to be JVP-complete. In the presence of associativity and commutativity, the problems still remain NP-complete. But when 0 is also assumed to be the unity for the function f, the problems are solvable in polynomial time. We also show that the problem remains in P even when a homomorphism is added. Second-order matching modulo nilpotence is shown to be undecidable.
Some of the results reported here are in partial fulfillment of Qing Guo's Ph.D. requirements, and will form part of his dissertation. Paliath Narendran was partially supported by NSF grant CCR-9404930.
We are currently working on an implementation of the algorithm for ACUNh-unification, as part of a unification workbench we are developing at the University at Albany (SUNY).
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Guo, Q., Narendran, P., Wolfram, D.A. (1996). Unification and matching modulo nilpotence. In: McRobbie, M.A., Slaney, J.K. (eds) Automated Deduction — Cade-13. CADE 1996. Lecture Notes in Computer Science, vol 1104. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-61511-3_90
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