Marta Kwiatkowska , Ulrich Herzog Christoph Meinel , Moshe Vardi ( editors )

ion in Probabilistic Process Algebra Suzana Andova Eindhoven University of Technology In this work we treat the problem of abstraction in fully probabilistic process algebra and its semantics based on branching bisimulation. Since the idea of fairness rules together with abstraction (introduced by the abstraction operator tauI and constant tau meaning an internal action) is central to the verification techniques in process algebra we introduce verification rules in fully probabilistic process algebra that arise rather in a natural way from the one defined in standard process algebra. These rules express the idea that due to a non-zero probability for a system to execute an external action, abstraction from internal step will yield the external step(s) with probability 1 after finitely many repetitions. The new result in our approach is the definition of a probabilistic branching bisimulation that