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A Sound and Complete Projection for Global Types

Authors Dawit Tirore, Jesper Bengtson, Marco Carbone

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Author Details

Dawit Tirore
  • IT University of Copenhagen, Denmark
Jesper Bengtson
  • IT University of Copenhagen, Denmark
Marco Carbone
  • IT University of Copenhagen, Denmark

Cite AsGet BibTex

Dawit Tirore, Jesper Bengtson, and Marco Carbone. A Sound and Complete Projection for Global Types. In 14th International Conference on Interactive Theorem Proving (ITP 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 268, pp. 28:1-28:19, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2023)


Multiparty session types is a typing discipline used to write specifications, known as global types, for branching and recursive message-passing systems. A necessary operation on global types is projection to abstractions of local behaviour, called local types. Typically, this is a computable partial function that given a global type and a role erases all details irrelevant to this role. Computable projection functions in the literature are either unsound or too restrictive when dealing with recursion and branching. Recent work has taken a more general approach to projection defining it as a coinductive, but not computable, relation. Our work defines a new computable projection function that is sound and complete with respect to its coinductive counterpart and, hence, equally expressive. All results have been mechanised in the Coq proof assistant.

Subject Classification

ACM Subject Classification
  • Theory of computation → Type theory
  • Computing methodologies → Distributed programming languages
  • Theory of computation → Program verification
  • Session types
  • Mechanisation
  • Projection
  • Coq


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