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.

In a SimEvents model, where there are SimEvents blocks and Simulink® blocks, the badge denotes the transition between time-based and event-based behavior. (A badge is an icon the software uses to flag issues or transitions.)

These storage blocks hold entities as they move through a model:

  • Entity generators

  • Queues

  • Servers

  • Terminators


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.

The table shows examples of entities in sample applications.

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 multistep process (that entities undergo) is most susceptible to failure?


SimEvents entities are fundamentally the same as Stateflow® messages.

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