Chapter 6 Process View Modeling Using the KSL

LEARNING OBJECTIVES

• To be able to understand the process view perspective compared to the event view

• To be able model discrete-event dynamic systems using the process view

• To be able build process view models using the KSL

There are essentially two fundamental viewpoints for modeling a discrete event system within simulation: the event view and the process view. Chapter 4 presented the event view. This chapter will present the process view. These views are simply different representations for the same system. In the event view, the system and its elements are conceptualized as reacting to events. In the process view, the movement of entities through their processes implies the events within the system in the system.

In discrete-event dynamic systems, an event is something that happens at an instant in time which corresponds to a change in system state. An event can be conceptualized as a transmission of information that causes an action resulting in a change in system state. In the event view, we directly modeled the system state by identifying the events and specifying the state changes. In the process view, the events will be implied by the action of entities within the system. An entity is an object of interest that moves through the system. Entities experience processes as they experience the system. In the simplest sense, a process can be thought of as a sequence of activities, where an activity is an element of the system that takes an interval of time to complete. In the pharmacy example, the service of the customer by the pharmacist was an activity. The representation of the dynamic behavior of the system by describing the process flows of the entities moving through the system is called process-oriented modeling. The modeling perspective based on identifying and describing the system’s processes is called the process-view.