ACID-Unification is NEXPTIME-Decidable
Résumé
We consider the unification problem for the equational theory AC(U)ID obtained by adjoining a binary `*' which is distributive over an associative-commutative idempotent operator `+', possibly admitting a unit element U. We formulate the problem as a particular class of set constraints, and propose a method for solving it by using the dag automata introduced by W. Charatonik, that we enrich with labels for our purposes. AC(U)ID-unification is thus shown to be in NEXPTIME.