Globally Governed Session Semantics

TL;DR

This paper introduces a new bisimulation theory for multiparty session types that accounts for global choreography specifications, enabling more precise reasoning about complex, large-scale distributed systems with multiple interleaved sessions.

Contribution

It presents a globally governed bisimulation that is more fine-grained than standard session bisimulation, with proven compositionality and practical application in large-scale distributed systems.

Findings

The governed bisimulation is strictly more fine-grained than standard bisimulation.

It is compositional, with soundness and completeness proofs.

Demonstrated application in large-scale cyberinfrastructure.

Abstract

This paper proposes a bisimulation theory based on multiparty session types where a choreography specification governs the behaviour of session typed processes and their observer. The bisimulation is defined with the observer cooperating with the observed process in order to form complete global session scenarios and usable for proving correctness of optimisations for globally coordinating threads and processes. The induced bisimulation is strictly more fine-grained than the standard session bisimulation. The difference between the governed and standard bisimulations only appears when more than two interleaved multiparty sessions exist. This distinct feature enables to reason real scenarios in the large-scale distributed system where multiple choreographic sessions need to be interleaved. The compositionality of the governed bisimilarity is proved through the soundness and completeness with respect to the governed reduction-based congruence. Finally, its usage is demonstrated by a thread transformation governed under multiple sessions in a real usecase in the large-scale cyberinfrustracture.