A theory of composing protocols

Bocchi, L., Orchard, D. and Voinea, A. L. (2022) A theory of composing protocols. Art, Science, and Engineering of Programming, 7(2), 6. (doi: 10.22152/programming-journal.org/2023/7/6)

Abstract

In programming, protocols are everywhere. Protocols describe the pattern of interaction (or communication) between software systems, for example, between a user-space program and the kernel or between a local application and an online service. Ensuring conformance to protocols avoids a significant class of software errors. Subsequently, there has been a lot of work on verifying code against formal protocol specifications. The pervading approaches focus on distributed settings involving parallel composition of processes within a single monolithic protocol description. However we observe that, at the level of a single thread/process, modern software must often implement a number of clearly delineated protocols at the same time which become dependent on each other, e.g., a banking API and one or more authentication protocols. Rather than plugging together modular protocol-following components, the code must re-integrate multiple protocols into a single component. We address this concern of combining protocols via a novel notion of ‘interleaving’ composition for protocols described via a process algebra. User-specified, domain-specific constraints can be inserted into the individual protocols to serve as ‘contact points’ to guide this composition procedure, which outputs a single combined protocol that can be programmed against. Our approach allows an engineer to then program against a number of protocols that have been composed (re-integrated), reflecting the true nature of applications that must handle multiple protocols at once. We prove various desirable properties of the composition, including behaviour preservation: that the composed protocol implements the behaviour of both component protocols. We demonstrate our approach in the practical setting of Erlang, with a tool implementing protocol composition that both generates Erlang code from a protocol and generates a protocol from Erlang code. This tool shows that, for a range of sample protocols (including real-world examples), a modest set of constraints can be inserted to produce a small number of candidate compositions to choose from. As we increasingly build software interacting with many programs and subsystems, this new perspective gives a foundation for improving software quality via protocol conformance in a multi-protocol setting.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: VOINEA, Laura
• Authors: Bocchi, L., Orchard, D., and Voinea, A. L.
• College/School: College of Science and Engineering
• Journal Name: Art, Science, and Engineering of Programming
• Publisher: Aspect-Oriented Software Association (AOSA)
• ISSN: 2473-7321
• Copyright Holders: Copyright © 2022 The Authors
• First Published: First published in Art, Science, and Engineering of Programming 7(2):6
• Publisher Policy: Reproduced under a Creative Commons License