8 th Workshop on Process Algebra and Stochastically Timed Activities PASTA 2009

Discreteness and continuity are two opposite ways of describing the world. However, there are many situations, from engines to cells, in which an hybrid description, mixing both such ingredients, seems more adequate. In this presentation, we focus on stochastic hybrid systems. We present Piecewise Deterministic Markov Processes, and we provide a simpler description language, Transition-Driven Stochastic Hybrid Automata. Then, we will see how such formalism can be used to define in a simple way a stochastic hybrid semantics for HYPE (an hybrid process algebra focussing on flows) and for PEPA. Finally, we discuss convergence theorems for the PEPA case.