Execution conditions: A formalization of event cancellation in simulation graphs

Simulation graph models provide a powerful and general modeling framework for discrete-event simulation. Within this framework it has been shown that an event-cancellation construct is a modeling convenience rather than a necessary modeling tool. As a result, very little work on the formal development of simulation graph models directly considers an event-canceling construct. However, to the simulation practitioner, the modeling convenience and functionality provided by a canceling construct is important. This is clearly demonstrated by the presence of some sort of event-canceling construct in all the major simulation software packages. This paper extends the simulation graph modeling framework to include a general approach to handling event cancellation. The extension is provided in algorithmic form. We demonstrate how the algorithm can be implemented in event graphs (and the corresponding commercial software SIGMA) and in the commercial software SIMAN.