Actor (UML)

In the Unified Modeling Language (UML), an actor is something or someone who supplies a stimulus to the system. It can also be thought of as something the system requires in order to function. Without a customer (an actor) in a restaurant, the process of ordering food cannot begin.

In addition to actors there also exist primary actors.

Primary Actors interact directly with a system to achieve their goals. Supporting actors may be humans or systems called in to support the Primary Actor.

Stakeholders can also be modelled as actors. They do not directly interact with the system but they are affected by the success of Primary Actor interactions.

We differentiate active actors, who initiate interactions with a system, and passive actors, who are targets of requests or who are activated by the system.