Synthesis of coordination programs from linear temporal logic

This paper presents a method for synthesizing a reactive program which coordinates the actions of a group of other reactive programs, so that the combined system satisfies a temporal specification of its desired long-term behavior. Traditionally, reactive synthesis has been applied to the construction of a stateful hardware circuit. This work is motivated by applications to other domains, such as the IoT (the Internet of Things) and robotics, where it is necessary to coordinate the actions of multiple sensors, devices, and robots. The mathematical model represents such entities as individual processes in Hoare's CSP model. Given a network of interacting entities, called an \emph{environment}, and a temporal specification of long-term behavior, the synthesis method constructs a \emph{coordinator} process (if one exists) that guides the actions of the environment entities so that the combined system is deadlock-free and satisfies the given specification. The main technical challenge is that a coordinator may have only \emph{partial knowledge} of the environment state, due to non-determinism within the environment, and environment actions that are hidden from the coordinator. This is the first method to handle both sources of partial knowledge, and to do so for arbitrary linear temporal logic specifications. It is shown that the coordination synthesis problem is \PSPACE-hard in the size of the environment. A prototype implementation is able to synthesize compact solutions for a number of coordination problems.