Predictable integration and reuse of executable real-time components

We present the concept of runnable virtual node (RVN) as a means to achieve predictable integration and reuse of executable real-time components in embedded systems. A runnable virtual node is a coarse-grained software component that provides functional and temporal isolation with respect to its environment. Its interaction with the environment is bounded both by a functional and a temporal interface, and the validity of its internal temporal behaviour is preserved when integrated with other components or when reused in a new environment. Our realization of RVN exploits the latest techniques for hierarchical scheduling to achieve temporal isolation, and the principles from component-based software-engineering to achieve functional isolation. It uses a two-level deployment process, i.e. deploying functional entities to RVNs and then deploying RVNs to physical nodes, and thus also gives development benefits with respect to composability, system integration, testing, and validation. In addition, we have implemented a server-based inter-RVN communication strategy to not only support the predictable integration and reuse properties of RVNs by keeping the communication code in a separate server, but also increasing the maintainability and flexibility to change the communication code without affecting the timing properties of RVNs. We have applied our approach to a case study, implemented in the ProCom component technology executing on top of a FreeRTOS-based hierarchical scheduling framework and present the results as a proof-of-concept.