Mining assumptions for synthesis

Automatic synthesis of a reactive system from its formal specification is appealing but often difficult due to the tedium of writing auxiliary specifications, especially on the environment. In several instances, specifications are found unrealizable as a result of insufficient environmental assumptions. We present an approach to this problem for synthesis from LTL based on specification mining. For a satisfiable but unrealizable specification, a counter-strategy can be computed from the synthesis game as a witness to unrealizability. Our algorithm mines environment assumptions from this counter-strategy as well as user scenarios if they are provided. We argue that our approach is a natural way to discover the designer's intent. We demonstrate the effectiveness of our approach on examples from the domains of digital circuits and robotic controllers.