Certifying Data in Multiparty Session Types

Abstract

Multiparty session types (MPST) are a typing discipline for ensuring the coordination of multi-agent communication in concurrent and distributed programs. The original MPST framework mainly focuses on the communication aspects of concurrency, unable to capture important data invariants in communicating programs. This work introduces value dependent types to the MPST framework in order to increase its expressiveness for certifying invariants of data exchanged among multiple participants. The key idea is to impose constraints on the exchanged data, which is explicitly witnessed at runtime by proof objects. The enriched MPST framework provides programmers with a precise global description of the interaction and data dependent patterns, from which local (data dependent) descriptions can be automatically generated for each endpoint, faithfully capturing at a local level the global data constraints. The framework ensures the absence of communication errors and guarantees communication progress in well-typed multiparty sessions. We also develop an extension of value dependencies based on proof irrelevance that enables the selective erasure of proof objects at runtime.

Observed Communication Semantics for Classical Processes

“…Dependent types for logically-based session-typed calculi have already been investigated by Toninho, Caires and Pfenning [33] and Toninho and Yoshida [34]. However, these calculi enforce a strict separation between data and communication: there are session types Πx:τ.A(x) and Σx:τ.A(x) which correspond to receiving or transmitting a value of value type τ .…”

A session type provider: compile-time API generation of distributed protocols with refinements in F#

“…We shall collectively refer to such features as interaction refinements, aspects of which have been studied across a range of separate theoretical systems, e.g. [2,4,29]. To date, there has been no work on formulating or implementing session types with such refinements in practice.…”

Chaperone contracts for higher-order sessions

“…Bocchi et al [2010] and Toninho and Yoshida [2016] extend global types with assertions to specify constraints on values communicated in a multiparty session. These approaches are based on a top-down methodology whereby the whole multiparty interaction is designed at once and then projected on the single participants of the session.…”

“…The session type is inferred automatically from the structure of the program. Bocchi et al [2010] use a decidable assertion logic and Toninho and Yoshida [2016] use dependent session types along the lines of Toninho et al [2011]. These choices make it possible to verify the correctness of participants statically.…”