Abstract
We show that every relation realised by a nondeterministic two-way transducer contains a function with equal domain which can be realised by a sequential two-way transducer. Our proof is built on three structural constructions with automata: a variant of Shepherdson’s method to convert a two-way automaton into an equivalent one-way automaton, which we call the folding of a two-way automaton; the construction of an unambiguous automaton for a rational language based on covering of automata; a simulation of an unambiguous automaton by a deterministic two-way one due to Hopcroft and Ullman. It follows a new proof for the fact (due to Engelfriet and Hoogeboom) that every functional two-way transducer can be converted into a sequential one, together with a clear estimation for the underlying complexity.
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de Souza, R. (2013). Uniformisation of Two-Way Transducers. In: Dediu, AH., Martín-Vide, C., Truthe, B. (eds) Language and Automata Theory and Applications. LATA 2013. Lecture Notes in Computer Science, vol 7810. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-37064-9_48
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DOI: https://doi.org/10.1007/978-3-642-37064-9_48
Publisher Name: Springer, Berlin, Heidelberg
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