A Theory of Design-by-Contract for Distributed Multiparty Interactions

The approach known as Design by Contract (DbC) [23] promotes reliable software development through elaboration of type signatures for sequential programs with logical formulae. This paper presents an assertion method which generalises the notion of DbC to multiparty distributed interactions, enabling the specification and verification of distributed multiparty protocols, based on the π-calculus with full recursion. Centring on the notion of global assertions and their projections onto endpoint assertions, our method allows fully general specifications for typed sessions with session channel passing, constraining the content of the exchanged messages, the choice of subconversations to follow, and invariants on recursions. The paper presents key theoretical foundations of this framework, including a validation algorithm for consistency of global assertions and a sound and relatively complete compositional proof system for verifying a large class of processes against assertions.