Both Ways Rational Functions

  • Christian Choffrut
  • Bruno Guillon
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 9840)


We consider binary relations on words which can be recognized by finite two-tape devices in two different ways: the traditional way where the two tapes are scanned in the same direction and a new one where they are scanned in different directions. The devices of the former type define the family of rational relations, while those of the latter define an a priori really different family. We characterize the partial functions that are in the intersection of the two families. We state a conjecture for the intersection for general, nonfunctional, relations.


Rational relations Finite automata Two-way transducers Two-tape automata Word relations 


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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  1. 1.IRIF, CNRS and Université Paris 7 Denis DiderotParisFrance

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