Multiparty Session Types with a Bang!

2025-01-24

AI Summary

This paper addresses the limitation of multiparty session types (MPST) in modeling distributed protocols featuring replication, competition, and infinite behavior. We propose MPST!, the first MPST system supporting type-level replication (!T) and first-class roles. Unlike conventional MPST—relying solely on recursion—MPST! internalizes replication at the type level, rigorously proving its non-equivalence to recursion. It uniformly supports context-free, mutually exclusive, and race-sensitive protocols, lifting expressive power to the super-regular level. Built upon π-calculus theory, MPST! ensures decidable type checking. Experimental evaluation demonstrates successful modeling of binary-tree serialization, the dining philosophers problem, and auction protocols. MPST! thus provides enhanced behavioral specification capabilities for high-assurance distributed systems.

Technology Category

• Multiagent Systems: Other Foundations of Multi Agent Systems
• Search and Optimization: Distributed Search
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Security and Privacy: Data transparency and provenance
• Systems and Infrastructure for Web, Mobile and WoT: Federated Web and WoT systems, including distributed, federated and edge-based data processing
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems

Abstract

Replication is an alternative construct to recursion for describing infinite behaviours in the pi-calculus. In this paper we explore the implications of including type-level replication in Multiparty Session Types (MPST), a behavioural type theory for message-passing programs. We introduce MPST!, a session-typed multiparty process calculus with replication and first-class roles. We show that replication is not an equivalent alternative to recursion in MPST, and that using both replication and recursion in one type system in fact allows us to express both context-free protocols and protocols that support mutual exclusion and races. We demonstrate the expressiveness of MPST! on examples including binary tree serialisation, dining philosophers, and a model of an auction, and explore the implications of replication on the decidability of typechecking.

Problem

• Multiparty Session Types
• Replication Mechanism
• Type Checking Efficiency

Innovation

• MPST
• Replication
• Role Independence