What is the difference between actors and user roles?
The term “actor” is used in object-oriented software engineering, the Unified Process, and in UML. An actor can be any external user, including other systems; in usage-centered design, our interest is in just the human users. In UML and the UP, an actor is defined as a role played by a user, but this verbal legerdemain can lead to confusion. Just as it is important not to confuse screen actors with the characters they sometimes play, so it is vital in user interface design to distinguish the roles in relation to a system from the actual people who may play them. To avoid confusion with UML terminology, we call the actual person who plays a particular user role the “role occupant.” We use the term “system actor” to refer to the non-human actors interacting with a system. See also UML/UP.
