We study the modeling and the o -line validation of real-time applications in uniprocessor environment, wich take explicitly the exchange of messages, resource sharing and conditional statements into account. Our goal is to highlight the impact of these parameters on the analysis of applications. Classically, these applications are modeled linearly, encapsulating the conditional blocks, and the scheduling sequences are used for validation. We propose an arborescent approach for modeling and validation, which allow us to consider explicitly the conditional blocks, and use the scheduling trees for validation. We then compare these two approaches of validation, and we prove that the linear validations approaches may be too pessimistic, meaning they can lead to declare certain applications such as non schedulable, when in fact they are schedulable. We beging by building a generator of valid valid scheduling trees. The complexity of the generator being exponential in the number of application tasks, this approach is di cult to implement in practice. So, we propose an approach for modeling, based on Petri nets. This Petri net will be used to generate the valid scheduling trees, by construction of the markings graph, and the complexity can be reduced by heuristics.
