Coalgebraic Theory of Büchi and Parity Automata: Fixed-Point Specifications, Categorically (Invited Tutorial)

Author Ichiro Hasuo

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Ichiro Hasuo
  • National Institute of Informatics, Japan

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Ichiro Hasuo. Coalgebraic Theory of Büchi and Parity Automata: Fixed-Point Specifications, Categorically (Invited Tutorial). In 29th International Conference on Concurrency Theory (CONCUR 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 118, pp. 5:1-5:2, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)


Coalgebra is a categorical modeling of state-based dynamics. Final coalgebras - as categorical greatest fixed points - play a central role in the theory; somewhat analogously, most coalgebraic proof techniques have been devoted to greatest fixed-point properties such as safety and bisimilarity. In this tutorial, I introduce our recent coalgebraic framework that accommodates those fixed-point specifications which are not necessarily the greatest. It does so specifically by characterizing the accepted languages of Büchi and parity automata in categorical terms. We present two characterizations of accepted languages. The proof for their coincidence offers a unique categorical perspective of the correspondence between (logical) fixed-point specifications and the (combinatorial) parity acceptance condition.

Subject Classification

ACM Subject Classification
  • Theory of computation → Automata over infinite objects
  • Coalgebra
  • category theory
  • fixed-point logic
  • automata
  • Büchi automata
  • parity automata


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