Department of Electrical and Electronic Engineering University of Western Australia

The implementation of Hierarchical Timed Petri Net (HTPN) in our system modelling tool yields a hierarchical analysis method, namely a Hierarchical Reachability State Diagram (HRSD). A Reachability State Diagram (RSD) can be generated for each subnet, and the number of tokens in each H-Block are also record in the state markings. Since the intention of using a HTPN hierarchical representation is to distribute the complexity of a single net over a set of subnets, the HRSD generated for each subnet may also contribute to solving the state explosion problem when representing the system state transitions in a single diagram. An algorithm is outlined to link these HRSDs of the subnets to model the state transitions of the overall system so that the state changes from one H-Block or subnet to another can be linked. Further state search can be performed to locate the sets of states which hold a similar properties to form a group of composition states corresponding to the states in the State Transition Diagram (STD) in which the system design is based on. Hence, the reachable states generated from system model simulation can be checked against the STD of the system specification to confirmed the correctness of the system design.