Time, causality, and realizability: Engineering interactive, distributed software systems

Today, software systems are distributed, concurrent, interactive, embedded, and often time-critical. They communicate and cooperate by data exchange. Introducing notions of time, causality, and realizability into interface-based data flow models results into a powerful model for engineering cyber-physical and, generally, distributed software systems. Architectures and their specification are designed by the concurrent composition of systems. This approach provides high expressive power supporting explicitly specification of interface behavior, encapsulation, abstraction, refinement, verification, concurrent composition, and modularity. The key idea is a formal, semantically coherent modelling, and specification framework that integrates the specification of timecritical and non-time-critical software embedded into cyber-physical systems. The approach supports the refinement of interface specifications of non-time-critical systems into interface specifications of time-critical systems and vice versa. This leads to an integrated specification and design approach for time-critical data flow architectures with soft, firm as well as hard time-critical requirements.