One of the important aspects of schedulability analysis is the model used to describe the system and its timing behavior. On one side, the accuracy of the test strongly depends on the accuracy of the model. On the other side, a detailed model could lead to an inaccaptable evaluation time. In this paper we propose a new model, the hierarchical event streams, which allows a high accuracy. We provide an efficient feasibility test for the model based on the context of demand and request bound function. Additionally we will provide a methodology to extract this model out of a control-flow graph efficiently. Together this allows a more accurate and efficient schedulability analysis of event driven real- time systems.