Hierarchical Stochastic Activity Networks

Stochastic activity networks (SANs) are a powerful and flexible extension of Petri nets. These models can be used for the modeling and analysis of various kinds and different aspects of distributed real-time systems. Similar to other classical extensions of Petri nets, SANs have some limitations for modeling complex and largescale systems. In order to remove these limitations and provide some high-level modeling facilities, we have defined a new extension for SANs, which is called hierarchical stochastic activity networks (HSANs). HSAN models provide facilities for composing a hierarchy of submodels, incremental modeling and the reusability of submodels. HSAN models encapsulate hierarchies and a key benefit of these models is the possibility of automatic employment of composition techniques by their modeling tool. In this paper, we present the graphical notations, formal definition, and methods for the analysis of HSAN models. We also present an example of the application of these models in the design of a high-capacity packet-based telecommunication switch. keywords: Stochastic Petri Nets, Stochastic Activity Networks, High-Level Petri Nets, Hierarchical Modeling.