A Practical Guide to SysML, 2nd Edition

12.3 Using Actors to Represent the Users of a System

An actor is used to represent the role of a human, an organization, or any external system that participates in the use of some system. Actors may interact directly with the system or indirectly through other actors.

It should be noted that “actor” is a relative term because an actor who is external to one system may be internal to another. For example, assume individuals in an organization request services from an internal help desk department that provides IT support for the organization. The help desk is considered the system and the members of the organization who are requesting service are considered the actors. However, these same individuals may in turn be providing services to an external ...