Scenarios@run.time - Distributed Execution of Specifications on IoT-connected Robots

In many areas we find cyber-physical systems consisting of multiple software-controlled components that communicate to control complex physical processes. As customers demand increasingly rich functionality, the component interactions become more and more complex. We are developing a formal scenario-based method for specifying the inter-component behavior that extends the concepts of Live Sequence Charts. This method is intuitive, yet precise, and automated analysis capabilities help engineers deal with the aforementioned complexity. In particular, the execution via the play-out algorithm supports a simulation of the behavior emerging from the interplay of the scenarios. Deriving a distributed implementation from an inter-component specification, however, is a challenging task. An alternative is the play-out of the specification by the distributed system. In this paper, we present a distributed play-out approach where the components coordinate via MQTT, a protocol used in IoT applications. We demonstrate the approach by a Car-to-X example implemented on Raspberry Pi-based robots.