A Theory of Formal Choreographic Languages

TL;DR

This paper introduces a comprehensive formal framework called formal choreographic languages for analyzing message-passing systems, unifying existing models and enabling the study of complex, non-regular behaviors.

Contribution

It develops a meta-model for formal choreographic languages that generalizes existing systems and provides conditions for correctness and communication properties.

Findings

Formal choreographic languages can model non-regular behaviors.

The framework unifies various existing formalisms like FSMs and session types.

Conditions for deadlock-freedom and other properties are established.

Abstract

We introduce a meta-model based on formal languages, dubbed formal choreographic languages, to study message-passing systems. Our framework allows us to generalise standard constructions from the literature and to compare them. In particular, we consider notions such as global view, local view, and projections from the former to the latter. The correctness of local views projected from global views is characterised in terms of a closure property. We consider a number of communication properties -- such as (dead)lock-freedom -- and give conditions on formal choreographic languages to guarantee them. Finally, we show how formal choreographic languages can capture existing formalisms; specifically we consider communicating finite-state machines, choreography automata, and multiparty session types. Notably, formal choreographic languages, differently from most approaches in the literature, can naturally model systems exhibiting non-regular behaviour.