COMPOSITIONAL VALIDATION OF TIME-CRITICAL SYSTEMS USING COMMUNICATING TIME PETRI NETS

An extended Petri Net model which considers modular partitioning along with timing restrictions and environment models is presented. Module constructs permit the specification of a complex system as a set of message passing modules with the timing semantics of Time Petri Nets. The state space of each individual module can be separately enumerated and assessed under the assumption of a partial specification of the intended module operation environment. State spaces of individual modules can be recursively integrated, to permit the assessment of module clusters and of the overall model, and to check the satisfaction of the assumptions made in the separate analysis of elementary component modules. In the intermediate stages between subsequent integration steps, the state spaces of module and module clusters can be projected onto reduced representations concealing local events that are not essential to the purposes of the analysis. The joint use of incremental enumeration and intermediate concealment of local events allows for a flexible management of state explosion, and permits a scalable approach to the validation of complex systems.