A New Model for Hard Real-Time Systems

In this paper we study hard real-time systems composed of periodic preemptive tasks and address the scheduling problem on specific hardware platforms. For such a system, the failure to satisfy any constraint may have disastrous consequences. An important starting point for the analysis of such systems is the basic task model considered. In this paper we introduce a new model, relative to the ones in the literature, that is able to obtain stronger schedulability conditions. This new model provides a formal and rigorous specification of a task and helps us to de-scribe the schedulability principle when tasks are scheduled by using a fixed-priority scheduling policy