Single-Use Automata and Transducers for Infinite Alphabets

Authors Mikołaj Bojańczyk, Rafał Stefański

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Mikołaj Bojańczyk
  • Institute of Informatics, University of Warsaw, Poland
Rafał Stefański
  • Institute of Informatics, University of Warsaw, Poland

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Mikołaj Bojańczyk and Rafał Stefański. Single-Use Automata and Transducers for Infinite Alphabets. In 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 168, pp. 113:1-113:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


Our starting point are register automata for data words, in the style of Kaminski and Francez. We study the effects of the single-use restriction, which says that a register is emptied immediately after being used. We show that under the single-use restriction, the theory of automata for data words becomes much more robust. The main results are: (a) five different machine models are equivalent as language acceptors, including one-way and two-way single-use register automata; (b) one can recover some of the algebraic theory of languages over finite alphabets, including a version of the Krohn-Rhodes Theorem; (c) there is also a robust theory of transducers, with four equivalent models, including two-way single use transducers and a variant of streaming string transducers for data words. These results are in contrast with automata for data words without the single-use restriction, where essentially all models are pairwise non-equivalent.

Subject Classification

ACM Subject Classification
  • Theory of computation → Formal languages and automata theory
  • Automata
  • semigroups
  • data words
  • orbit-finite sets


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