Active element external to the system, and cooperating with it.
An Actor is an idealization of an external person, process or thing interacting with a system, subsystem or class. An Actor characterizes the interactions that outside users may have with the system. An Actor may be a human, an external software component or a device that cooperates with the system. Actors can have Communication links with UseCases. They can also communicate with other Actors (Modelio extension to UML). Actors can appear in sequence diagrams (see Example2) or collaboration diagrams, where accurate communication with the system's objects is shown. An Actor is a specific kind of Classifier. An Actor can have Generalization links with other Actors, can have Attributes and even Operations. In Modelio, an Actor physically belongs to a NameSpace that must be a Package.
: Actor (architecture_autodiagram)
Figure 178 : Actor (architecture_autodiagram)