A schedule of a Petri Net (PN) represents a set of firing sequences that can be infinitely repeated within a bounded state space, regardless of the outcomes of the nondeterministic choices. Schedulability analysis for a given PN answers the question whether a schedule exists in the reachability space of this net. This paper suggests a novel approach for schedulability analysis based solely on PN structure. It shows that unschedulability can be caused by a structural relation among transitions modelling nondeterministic choices. A method based on linear programming for checking this relation is proposed. This paper also presents a necessary condition for schedulability based on the rank of the incidence matrix of the underlying PN. These results shed a light on the sources of unschedulability often found in PN models of embedded multimedia systems.
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This paper presents a synthesis approach for reactive systems that aims at minimizing the overhead introduced by the operating system and the interaction among the concurrent tasks, while considering multiple concurrent execution resources. A formal model based on the notion of scheduling of Petri nets is used to perform the synthesis. We show how the notion of projections of a schedule for the complete system onto the components implemented on separate resources is essential to define the correctness of the partitioned schedule.
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