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What Is an Entity?

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 ApplicationEntities
Airport with a queue for runway accessAirplanes waiting for access to runway
Communication networkPackets, frames, or messages to transmit
Bank of elevatorsPeople traveling in elevators
Conveyor belt for assembling partsParts to assemble
Computer operating systemComputational 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?

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