Two-Head Finite-State Acceptors with Translucent Letters

  • Benedek Nagy
  • Friedrich OttoEmail author
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 11376)


Finite-state acceptors are studied that have two heads that read the input from opposite sides. In addition, a set of translucent letters is associated with each state. It is shown that these two-head automata are strictly more expressive than the model with a single head, but that they still only accept languages that have a semi-linear Parikh image. In fact, we obtain a characterization for the class of linear context-free trace languages in terms of a specific class of two-head finite-state acceptors with translucent letters.


Two-head finite-state acceptor Translucent letter Linear context-free language Semi-linear Parikh set Trace language 


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Authors and Affiliations

  1. 1.Department of Mathematics, Faculty of Arts and SciencesEastern Mediterranean UniversityFamagustaTurkey
  2. 2.Fachbereich Elektrotechnik/InformatikUniversität KasselKasselGermany

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