On equational theories, unification and decidability
on Rewriting techniques and applications
Unification in commutative idempotent monoids
Theoretical Computer Science
Unification in a combination of arbitrary disjoint equational theories
Journal of Symbolic Computation
Unification in the union of disjoint equational theories: combining decision procedures
Journal of Symbolic Computation
Term rewriting and all that
Fast Decision Procedures Based on Congruence Closure
Journal of the ACM (JACM)
Introduction to Automata Theory, Languages and Computability
Introduction to Automata Theory, Languages and Computability
Journal of Automated Reasoning
Unification in the Union of Disjoint Equational Theories: Combining Decision Procedures
CADE-11 Proceedings of the 11th International Conference on Automated Deduction: Automated Deduction
Hi-index | 0.00 |
We present a solution to Problem #66 from the RTA open problem list. The question is whether there exists an equational theory E such that E-unification with constants is decidable but general E-unification is undecidable. The answer is positive and we show such a theory. The problem has several equivalent formulations, therefore the solution has many consequences. Our result also shows, that there exist two theories E 1 and E 2 over disjoint signatures, such that E 1-unification with constants and E 2-unification with constants are decidable, but (E 1驴驴驴E 2)-unification with constants is undecidable.