A Game Interpretation of Retractable Contracts

In the setting of contract theory, retractable contracts have been defined to formalize binary session protocols where the partners can go back to certain particular synchronization points when the ses- sion gets stuck, looking for a successful state, if any. In the present paper we propose a three-party game-theoretic inter- pretation of client/server systems of retractable contracts. In particular, we show that a client is retractable-compliant with a server if and only if there exists a winning strategy for a particular player in a game-theoretic model of contracts. Such a player can be looked at as a mediator, driving the choices in the retractable points. We show that winning strategies for the mediator player correspond to orchestrators in a system of orches- trated client/server sessions, and vice versa.