An Algebraic Characterization of Unary Two-Way Transducers

  • Christian Choffrut
  • Bruno Guillon
Part of the Lecture Notes in Computer Science book series (LNCS, volume 8634)


Two-way transducers are ordinary finite two-way automata that are provided with a one-way write-only tape. They perform a word to word transformation. Unlike one-way transducers, no characterization of these objects as such exists so far except for the deterministic case. We study the other particular case where the input and output alphabets are both unary but when the transducer is not necessarily deterministic. This yields a family which extends properly the rational relations in a very natural manner. We show that deterministic two-way unary transducers are no more powerful than one-way transducers.


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Copyright information

© Springer-Verlag GmbH Berlin Heidelberg 2014

Authors and Affiliations

  • Christian Choffrut
    • 1
  • Bruno Guillon
    • 1
  1. 1.LIAFACNRS and Université Paris 7 Denis DiderotFrance

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