Towards Constructive Hybrid Semantics

Authors Tim Lukas Diezel, Sergey Goncharov

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Tim Lukas Diezel
  • FAU Erlangen-Nürnberg, Germany
Sergey Goncharov
  • FAU Erlangen-Nürnberg, Germany


We would like to thank anonymous referees for carefully reading the text and making various points which contributed to improving presentation, and also to Stefan Milius for references on conservative completion.

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Tim Lukas Diezel and Sergey Goncharov. Towards Constructive Hybrid Semantics. In 5th International Conference on Formal Structures for Computation and Deduction (FSCD 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 167, pp. 24:1-24:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)


With hybrid systems becoming ever more pervasive, the underlying semantic challenges emerge in their entirety. The need for principled semantic foundations has been recognized previously in the case of discrete computation and discrete data, with subsequent implementations in programming languages and proof assistants. Hybrid systems, contrastingly, do not directly fit into the classical semantic paradigms due to the presence of quite specific "non-programmable" features, such as Zeno behaviour and the inherent indispensable reliance on a notion of continuous time. Here, we analyze the phenomenon of hybrid semantics from a constructive viewpoint. In doing so, we propose a monad-based semantics, generic over a given ordered monoid representing the time domain, hence abstracting from the monoid of constructive reals. We implement our construction as a higher inductive-inductive type in the recent cubical extension of the Agda proof assistant, significantly using state-of-the-art advances of homotopy type theory. We show that classically, i.e. under the axiom of choice, our construction admits a charaterization in terms of directed sequence completion.

Subject Classification

ACM Subject Classification
  • Theory of computation → Categorical semantics
  • Theory of computation → Axiomatic semantics
  • Hybrid semantics
  • Elgot iteration
  • Homotopy type theory
  • Agda


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