Abstract. Bridging the gap between the specification of software requirements and actual execution of the behavior of the specified system has been the target of much research in recent years. We have created a natural language interface, which, for a useful class of systems, yields the automatic production of executable code from structured requirements. In this paper we describe how our method uses static and dynamic grammar for generating live sequence charts (LSCs), that constitute a powerful executable extension of sequence diagrams for reactive systems. We have implemented an automatic translation from controlled natural language requirements into LSCs, and we demonstrate it on two sample reactive systems.