Multiparty session types for distributed and failure-prone systems

Le Brun, Matthew Alan (2026) Multiparty session types for distributed and failure-prone systems. PhD thesis, University of Glasgow.

Abstract

Distributed computer systems inherently introduce notions of concurrency, nondeterminism and possibly failure-prone communication into programs. This makes designing, and implementing, correct distributed systems difficult, and it is widely agreed that such systems require rigorous methods of verification.

Types and type systems are lightweight techniques to formal verification whereby code implementations are annotated with meta-information about the data they use. This provides certain guarantees of correctness about the usage of data within a program, and helps developers design and implement code that is correct by construction. Specific to message-passing systems, session types not only describe information about what data is, but also about how it should be communicated. Essentially, they embed communication protocols as types within a program, ensuring that well-typed code abides by the specified protocol and benefits from any properties determined on said protocol, e.g. being deadlock-free, terminating, live, etc. Multiparty session types (MPST) are a generalisation of session type theory that allows for the description of communication protocols involving two or more named participants with possibly cyclic or interleaved communication patterns.

This thesis adapts MPST to describe protocols for distributed and failure-prone systems. The contributions presented are in the form of three novel languages: MPST!, MAGπ, and MAGπ!, each using a new MPST theory targetting client-server, failure-prone and fault-tolerant systems respectively; where the unit of failure is message loss and fault tolerance is introduced through the client-server paradigm.

This work establishes foundations for designing MPST systems targetted towards building multiparty client-server and fault-tolerant programs. For the first time, MPSTs are explored within programs designed to run over failure-prone networks, where messages are susceptible to loss, unbounded delay and total reordering. The construct of replication is shown to be expressively significant for building multiparty client-server systems. Lastly, it is demonstrated how combining replication, nondeterministic timeouts and standard MPST constructs, results in an expressive type system capable of modelling—and verifying properties on—fault-tolerant multiparty programs.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QA Mathematics > QA75 Electronic computers. Computer science
• Colleges/Schools: College of Science and Engineering > School of Computing Science
• Supervisor's Name: Dardha, Dr. Ornela and Fowler, Dr. Simon
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-85779
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 24 Feb 2026 10:03
• Last Modified: 27 Feb 2026 09:31
• Thesis DOI: 10.5525/gla.thesis.85779
• URI: https://theses.gla.ac.uk/id/eprint/85779

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