Real-Time Tasks in SDL

Abstract

SDL is a formal design language for distributed systems that is also promoted for real-time systems. To improve its real-time expressiveness, several language extensions have been proposed. In this work, we present an extension of SDL to specify real-time tasks, a concept used in real-time systems to structure and schedule execution. We model a real-time task in SDL as a hierarchical order of executions of SDL transitions, which may span different SDL processes. Real-time tasks are selected for execution using time-triggered and priority-based scheduling. We formally define real-time tasks, show their syntactical and semantical incorporation in SDL, present the implementation approach in our SDL tool chain, and provide excerpts of a complex MAC protocol showing the use of real-time tasks in SDL.