ABSTRACT
Despite the enormous flexibility of discrete event simulation (DES), a relatively small number of concepts underlie it (Table 2.1). These concepts are: the events that define the changes in the entities or in the state of the model; the entities that experience those events; the attributes that distinguish individual entities from one another; the explicit handling of resources and any resulting queues; and, perhaps most distinctively, the running of the model in continuous time. Other concepts are common across many types of models, not just DES: the use of information global to the entire model; distributions that represent a possible range of values and the frequency with which they occur; control logic governs the overall behavior of the system, including things like entity routing, resource availability, and status tests; branches describe alternative routes an individual may take based on either logical or probabilistic conditions; and sets are groups of like items, resources, entities, and so on.
