Generators and Bases for Monadic Closures

Authors Stefan Zetzsche, Alexandra Silva, Matteo Sammartino

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Author Details

Stefan Zetzsche
  • Amazon Web Services, London, UK
  • University College London, UK
Alexandra Silva
  • Cornell University, Ithaca, NY, USA
  • University College London, UK
Matteo Sammartino
  • Royal Holloway, University of London, UK
  • University College London, UK

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Stefan Zetzsche, Alexandra Silva, and Matteo Sammartino. Generators and Bases for Monadic Closures. In 10th Conference on Algebra and Coalgebra in Computer Science (CALCO 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 270, pp. 11:1-11:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


It is well-known that every regular language admits a unique minimal deterministic acceptor. Establishing an analogous result for non-deterministic acceptors is significantly more difficult, but nonetheless of great practical importance. To tackle this issue, a number of sub-classes of non-deterministic automata have been identified, all admitting canonical minimal representatives. In previous work, we have shown that such representatives can be recovered categorically in two steps. First, one constructs the minimal bialgebra accepting a given regular language, by closing the minimal coalgebra with additional algebraic structure over a monad. Second, one identifies canonical generators for the algebraic part of the bialgebra, to derive an equivalent coalgebra with side effects in a monad. In this paper, we further develop the general theory underlying these two steps. On the one hand, we show that deriving a minimal bialgebra from a minimal coalgebra can be realized by applying a monad on an appropriate category of subobjects. On the other hand, we explore the abstract theory of generators and bases for algebras over a monad.

Subject Classification

ACM Subject Classification
  • Theory of computation → Abstract machines
  • Monads
  • Category Theory
  • Generators
  • Automata
  • Coalgebras
  • Bialgebras


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