A Very Gentle Introduction to Multiparty Session Types

Communicating state machines provide a formal foundation for distributed computation. Unfortunately, they are Turing-complete and, thus, challenging to analyse. In this paper, we classify restrictions on channels which have been proposed to work around the undecidability of verification questions. We compare half-duplex communication, existential B-boundedness, and k-synchronisability. These restrictions do not prevent the communication channels from growing arbitrarily large but still restrict the power of the model. Each restriction gives rise to a set of languages so, for every pair of restrictions, we check whether one subsumes the other or if they are incomparable. We investigate their relationship in two different contexts: first, the one of communicating state machines, and, second, the one of communication protocol specifications using high-level message sequence charts. Surprisingly, these two contexts yield different conclusions. In addition, we integrate multiparty session types, another approach to specify communication protocols, into our classification. We show that multiparty session type languages are half-duplex, existentially 1-bounded, and 1-synchronisable. To show this result, we provide the first formal embedding of multiparty session types into high-level message sequence charts.

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“…Case (1). The semi-full merge s [63] can apply Cases (1) and (2). The full merge f [54] can apply all Cases (1), (2), and (3).…”

Section: Each Merge Operator Is Defined By a Collection Of Cases It C...mentioning

confidence: 99%

Comparing Channel Restrictions of Communicating State Machines, High-level Message Sequence Charts, and Multiparty Session Types

Stutz

Zufferey

2022

Electron. Proc. Theor. Comput. Sci.

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“…1. It follows three main steps [5,17]. First, a global type, also called a global protocol, is defined as a shared contract between communicating endpoint processes.…”

Section: From Binary To Multiparty Sessions In Rustmentioning

confidence: 99%

Implementing Multiparty Session Types in Rust

Lagaillardie

Neykova

Yoshida

2020

Lecture Notes in Computer Science

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Multiparty Session Types (MPST) is a typing discipline for distributed protocols, which ensures communication safety and deadlockfreedom for more than two participants. This paper reports on our research project, implementing multiparty session types in Rust. Current Rust implementations of session types are limited to binary (twoparty communications). We extend an existing library for binary session types to MPST. We have implemented a simplified Amazon Prime Video Streaming protocol using our library for both shared and distributed communication transports.

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“…Overview. Discourje is built on a formal foundation, inspired by process algebra (e.g., [15]) and multiparty session types (e.g., [46]). In a nutshell, let S and I be sets of specifications and implementations.…”

Section: Foundationmentioning

confidence: 99%

Safe Sessions of Channel Actions in Clojure: A Tour of the Discourje Project

Hamers

Jongmans

2020

Leveraging Applications of Formal Methods, Verification and Validation: Verification Principles

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To simplify shared-memory concurrent programming, in addition to low-level synchronisation primitives, several modern programming languages have started to offer core support for higherlevel communication primitives as well, in the guise of message passing through channels. Yet, a growing body of evidence suggests that channel-based programming abstractions for shared memory also have their issues. The Discourje project aims to help programmers cope with messagepassing concurrency bugs in Clojure programs, based on run-time verification and dynamic monitoring. The idea is that programmers write not only implementations, but also specifications (of sessions of channel actions). Discourje then offers a library to ensure that implementations run safely relative to specifications (= "bad" channel actions never happen). This paper gives a tour of the current state of Discourje, by example; it is intended to serve both as a general overview for readers who are unfamiliar with previous work on Discourje, and as an introduction to new features for readers who are familiar.

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A Very Gentle Introduction to Multiparty Session Types

Cited by 16 publications

References 18 publications

Comparing Channel Restrictions of Communicating State Machines, High-level Message Sequence Charts, and Multiparty Session Types

Comparing Channel Restrictions of Communicating State Machines, High-level Message Sequence Charts, and Multiparty Session Types

Implementing Multiparty Session Types in Rust

Safe Sessions of Channel Actions in Clojure: A Tour of the Discourje Project

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