Building reusable simulators using hierarchical event graphs

Hierarchical event graphs are an easy way to build special purpose simulators. At the lowest level, event graphs are created to represent particular components of the system being simulated; steps in a process flow, or hyper-events. These low-level graphs can then be viewed as different classes of vertices that make up the next higher level graph. A special purpose simulation toolkit is thus developed. Three very different types of hierarchical event-graph simulation toolkits are discussed in this article: a Petri net simulator that is used to teach the activity-scanning approach to simulation modeling; SIMAN and GPSS network simulators that are used to teach process interaction modeling and introduce these languages; and an industrial process simulator called QUALPLAN that is used for planning quality inspection systems