Introduction to Discrete Event Dynamic Systems

Picture yourself with the mythical Mr. T. S. Mits (T he S cientific M an I n T he S treet) and the task of explaining to him the phenomena and workings of (i) the Gulf Stream and (ii) a computer-controlled flexible manufacturing system (FMS). Both phenomena are real and both are not completely understood. However, for task (i), you face an easy assignment since you can draw upon a knowledge of calculus and differential equations to provide a succinct description of ocean currents and fluid dynamics. For task (ii), no such ready-made models are in existences1. One is essentially reduced to using an algorithmic description not very different from writing a computer program to simulate the FMS. In fact, modern technology has increasingly created dynamic systems which cannot be easily described by ordinary or partial differential equations. Examples of such systems are production or assembly lines, computer communication networks, traffic systems on both the air and land side of a large airport, military C3I (C ommand-C ontrol-C ommunication-I ntelligence) system, etc. The evolution of these systems in time depends on the complex interactions of the timing of various discrete events, such as the arrival or the departure of a job, and the initiation or the completion of a task or a message.