A classifier for entities outside a subject that interact directly with the subject. An actor participates in a use case or coherent set of use cases to accomplish an overall purpose.
See also use case.
An actor is a classifier that characterizes a role played by an outside user or related set of users with respect to a subject. The subject is also a classifier. An actor is an idealization with a focused purpose and meaning and might not correspond exactly to physical objects. One physical object may combine disparate purposes and therefore be characterized by several actors. Different physical objects may include the same purpose, and that aspect of them would be modeled by the same actor. The user object may be a human, a computer ...