Toward Verified Library-Level Choreographic Programming with Algebraic Effects

Abstract: Choreographic programming (CP) is a paradigm for programming distributed applications as single, unified programs, called choreographies, that are then compiled to node-local programs via endpoint projection (EPP). Recently, library-level CP frameworks have emerged, in which choreographies and EPP are expressed as constructs in an existing host language. So far, however, library-level CP lacks a solid theoretical foundation. In this paper, we propose modeling library-level CP using algebraic effects, an abstraction that generalizes the approach taken by existing CP libraries. Algebraic effects let us define choreographies as computations with user-defined effects and EPP as location-specific effect handlers. Algebraic effects also lend themselves to reasoning about correctness properties, such as soundness and completeness of EPP. We present a prototype of a library-level CP framework based on algebraic effects, implemented in the Agda proof assistant, and discuss our ongoing work on leveraging the algebraic-effects-based approach to prove the correctness of our library-level CP implementation.