The role of process abstraction in simulation

The concept of process abstraction, which allows simulationists to construct models composed of a set of interconnected levels, is discussed. Each level in the network represents the process at some given level of abstraction and is encoded using a model type (e.g. Petri net, automaton, data flow graph) appropriate to that level. An example process composed of articulated figures around a circular table is presented. After the process is formally defined at each level, the abstraction relationships between levels are discussed. A taxonomy of process abstraction methods is presented in an effort to characterize the fundamental concepts of level traversal. The application involving the animation of the process is described within the context of the HIRES simulation language that was constructed specifically to simulate and analyze multilevel simulations. Textual and graphical examples of HIRES output are included. Finally, some observations on the future of process abstraction in modeling are given