Abstract. Live Sequence Charts (LSCs) is a visual requirements language for specifying reactive system behavior. When modeling and designing open reactive systems, it is often essential to have a guarantee that the requirements can be satisfied under all possible circumstances. We apply results in the area of controller synthesis to a subset of the LSC language to decide the realizability of LSC requirements. If realizable, we show how to generate system responses that are guaranteed to satisfy the requirements. We discuss one particular implementation of this result which is formulated as an extension of smart play-out, a method for direct execution of scenario-based requirements.

Studies of biological systems are often facilitated by diagram models that summarize the current understanding of underlying mechanisms. The increasing complexity of our understanding of biology necessitates computational models that can extend these representations to include their dynamic behavior. We present here a new tool we call Synthesizing Biological Theories which enables biologists and modelers to construct high-level theories and models of biological systems, capturing biological hypotheses, inferred mechanisms, and experimental results within the same framework. Among the key features of the tool are convenient ways to represent several competing theories and the interactive nature of building and running the models using an intuitive, rigorous scenario-based visual language. The definition of the modeling language is geared towards enabling formal verification and analysis.

Live Sequence provide a formal frameworkfor creating scenario-based requirements for reactive systems. An imposes a partial order over a set of events, such as the sending or receiving of messages. Each event is associated with a liveness property, indicating whether it can or must occur. extensions can further when events should An individual LSC tells a story about particular fragment of system behavior, whereas specifications-a$nite set of define the total behavior. An m y require that more than one distinct scenario, or multiple instances of the same scenario, execute concurrently. It is natural to ask whether speccan be synthesized into formal languages. Previous work offers to nite state machines, single (non-concurrent) to automata. Here, we show that with concurrency can also be expressed as a timed

Live Sequence Charts (LSCs) is a scenario-based language for modeling object-based reactive systems with liveness properties. A tool called the Play-Engine allows users to create LSC requirements using a point-and-click interface and generate executable traces using features called playout and smart play-out. Finite executable trace fragments called super-steps are generated by smart play-out in response to user inputs. Each super-step is guaranteed not to violate the LSC requirements, provided one exists. However, non-violation is not guaranteed beyond each individual super-step. In this work, we demonstrate a powerful extension to smart play-out which produces only traces that are guaranteed not to violate the LSC requirements, provided the requirements are realizable. Using this method, we may synthesize correct executable programs directly from LSC requirements.