Entities may represent such things as jobs, cars, or other items. Associated with each entity is a set of attributes, denoted Each attribute is a number, but can be interpreted in many different ways. For instance, we might set might be the time the entity entered the system, might be 0 if the entity represents a business customer and 1 if it represents a private customer, is the service time of the entity, and so on. These entities flow through a system of blocks . Blocks describe the action an entity can take.
Resources represent machines, workers, and other items that handle entities.
Let's start with a very simple model. Suppose we want to analyze the behavior of the two Klunky automatic teller machine system we set up last class. A Klunky takes an average of 1.8 minutes to serve a customer. We are concerned with the average waiting time for the first hundred customers into the system. Our entities here are the customers.