Homotopy Type Theory in Isabelle

Author Joshua Chen

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Joshua Chen
  • University of Nottingham, UK

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Joshua Chen. Homotopy Type Theory in Isabelle. In 12th International Conference on Interactive Theorem Proving (ITP 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 193, pp. 12:1-12:8, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)


This paper introduces Isabelle/HoTT, the first development of homotopy type theory in the Isabelle proof assistant. Building on earlier work by Paulson, I use Isabelle’s existing logical framework infrastructure to implement essential automation, such as type checking and term elaboration, that is usually handled on the source code level of dependently typed systems. I also integrate the propositions-as-types paradigm with the declarative Isar proof language, providing an alternative to the tactic-based proofs of Coq and the proof terms of Agda. The infrastructure developed is then used to formalize foundational results from the Homotopy Type Theory book.

Subject Classification

ACM Subject Classification
  • Theory of computation → Logic and verification
  • Theory of computation → Type theory
  • Theory of computation → Higher order logic
  • Proof assistants
  • Logical frameworks
  • Dependent type theory
  • Homotopy type theory


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