Resolving Non-Determinism in Choreographies

Resolving non-deterministic choices of choreographies is a crucial task. We introduce a novel notion of realisability for choreographies –called whole-spectrum implementation– that rules out deterministic implementations of roles that, no matter which context they are placed in, will never follow one of the branches of a non-deterministic choice. We show that, under some conditions, it is decidable whether an implementation is whole-spectrum. As a case study, we analyse the POP protocol under the lens of whole-spectrum implementation

On Resolving Non-determinism in Choreographies

Choreographies specify multiparty interactions via message passing. A realisation of a choreography is a composition of independent processes that behave as specified by the choreography. Existing relations of correctness/completeness between choreographies and realisations are based on models where choices are non-deterministic. Resolving non-deterministic choices into deterministic choices (e.g., conditional statements) is necessary to correctly characterise the relationship between choreographies and their implementations with concrete programming languages. We introduce a notion of realisability for choreographies - called whole-spectrum implementation - where choices are still non-deterministic in choreographies, but are deterministic in their implementations. Our notion of whole spectrum implementation rules out deterministic implementations of roles that, no matter which context they are placed in, will never follow one of the branches of a non-deterministic choice. We give a type discipline for checking whole-spectrum implementations. As a case study, we analyse the POP protocol under the lens of whole-spectrum implementation

On Resolving Non-determinism in Choreographies

Choreographies specify multiparty interactions via message passing. A realisation of a choreography is a composition of independent processes that behave as specified by the choreography. Existing relations of correctness/completeness between choreographies and realisations are based on models where choices are non-deterministic. Resolving non-deterministic choices into deterministic choices (e.g., conditional statements) is necessary to correctly characterise the relationship between choreographies and their implementations with concrete programming languages. We introduce a notion of realisability for choreographies - called whole-spectrum implementation - where choices are still non-deterministic in choreographies, but are deterministic in their implementations. Our notion of whole spectrum implementation rules out deterministic implementations of roles that, no matter which context they are placed in, will never follow one of the branches of a non-deterministic choice. We give a type discipline for checking whole-spectrum implementations. As a case study, we analyse the POP protocol under the lens of whole-spectrum implementation

A gentle introduction to multiparty asynchronous session types

This article provides a gentle introduction to multiparty session types, a class of behavioural types specifically targeted at describing protocols in distributed systems based on asynchronous communication. The type system ensures well-typed processes to enjoy non-trivial properties, including communication safety, protocol fidelity, as well as progress. The adoption of multiparty session types can positively affect the whole software lifecycle, from design to deployment, improving software reliability and reducing its development costs

Composition and Decomposition of Multiparty Sessions

International audienceMultiparty sessions are systems of concurrent processes, which allow several participants to communicate by sending and receiving messages. Their overall behaviour can be described by means of global types. Typable multiparty sessions enjoy lock-freedom. We look at multiparty sessions as open systems by allowing one to compose multiparty sessions by transforming two of their participants into a pair of coupled gateways, forwarding messages between the two sessions. Gateways need to be compatible. We show that the session resulting from the composition can be typed, and its type can be computed from the global types of the starting sessions. As a consequence, lock-freedom is preserved by composition. Compatibility between global types is necessary, since systems obtained by composing sessions with incompatible global types have locks (or they are not sessions). We also define direct composition, which allows one to connect two global types without using gateways. Finally, we propose a decomposition operator, to split a global type into two, which is the left inverse of direct composition. Direct composition and decomposition on global types prepare the ground for a novel framework allowing for the modular design and implementation of distributed systems