A time Petri net approach for finding preruntime schedules in embedded hard real-time systems

There are two general approaches for scheduling tasks in real-time systems: runtime and preruntime scheduling. However, there are several situations where the runtime approach does not find a feasible schedule even when such a schedule exists. However, finding a feasible schedule is not trivial, because this problem is NP-hard in its general form. The proposed method finds a preruntime scheduling, when one exists, using state space exploration starting from a system formal model. Despite this technique being not new, at the best of our present knowledge, no one tried to use it for finding preruntime scheduling. The main problem with this approach is the space size, which can grow exponentially. This article shows how to minimize this problem. Additionally, the proposed algorithm is a depth-first search method on a labeled transition system derived from a time Petri net model. It is verified through real-world experimental results that the schedule is found examining a reduced number of states.