Composition Techniques for Tree Communication Schedules

A critical resource in a distributed real-time system is its shared communication medium. Unrestrained concurrent access to the network can lead to collisions that reduce the system s reliability. Therefore in this area, one goal is to develop effective models for coordinating and controlling access to the shared medium and its channels. Network Code is a verifiable, executable model for coordinating and controlling access to a shared communication medium in a distributed real-time system. In this paper, we investigate the problem of building an application by composing multiple Network Code programs. To reason about the composition, we model Network Code programs as Tree Schedules (TS) and then consider the composition of schedules that describe how the network is accessed by different applications. Specifically, we first define the notions of compatibility and composability of tree schedules, and then provide algorithms for their composition and reason about overhead of composition. We illustrate the techniques by considering the composition of two control applications.