Discrete-event simulations typically involve discrete items of interest. By definition, these items are called entities in SimEvents® software. Entities can pass through a network of queues, servers, gates, and switches during a simulation. Entities can carry data, known in SimEvents software as attributes.
Note: Entities are not the same as events. Events are instantaneous discrete incidents that change a state variable, an output, and/or the occurrence of other events. See What Is an Event? for details.
Examples of entities in some sample applications are in the table.
|Context of Sample Application||Entities|
|Airport with a queue for runway access||Airplanes waiting for access to runway|
|Communication network||Packets, frames, or messages to transmit|
|Bank of elevators||People traveling in elevators|
|Conveyor belt for assembling parts||Parts to assemble|
|Computer operating system||Computational tasks or jobs|
A graphical block can represent a component that processes entities, but entities themselves do not have a graphical representation. When you design and analyze your discrete-event simulation, you can choose to focus on:
The entities themselves. For example, what is the average waiting time for a series of entities entering a queue?
The processes that entities undergo. For example, which step in a multiple-step process (that entities undergo) is most susceptible to failure?