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Equivalence of Deterministic Top-Down Tree-to-String Transducers Is Decidable
2018
Journal of the ACM
We show that equivalence of deterministic top-down tree-to-string transducers is decidable, thus solving a long standing open problem in formal language theory. We also present efficient algorithms for subclasses: polynomial time for total transducers with unary output alphabet (over a given top-down regular domain language), and corandomized polynomial time for linear transducers; these results are obtained using techniques from multi-linear algebra. For our main result, we prove that
doi:10.1145/3182653
fatcat:ayyyao4j4ncfflbq6lboybjbru