actor : An Actor models a type of role played by an entity that interacts with the subjects of its associated UseCases (e.g., by exchanging signals and data). Actors may represent roles played by human users, external hardware, or other systems.
¶·NOTE. An Actor does not necessarily represent a specific physical entity but instead a particular role of some entity that is relevant to the specification of its associated UseCases. Thus, a single physical instance may play the role of several different Actors and, conversely, a given Actor may be played by multiple different instances.
(†2483)
actor (p. 645): An Actor specifies a role played by a user or any other system that interacts with the subject. (†2484)
association class (p. 197): An Association classifies a set of tuples representing links between typed instances. An AssociationClass is both an Association and a Class. . . .
¶ An Association specifies a semantic relationship that can occur between typed instances. It has at least two memberEnds represented by Properties, each of which has the type of the end. More than one end of the Association may have the same type. An Association declares that there can be links between instances whose types conform to or implement the associated types. A link is a tuple with one value for each memberEnd of the Association, where each value is an instance whose type conforms to or implements the type at the end.
(†2485)
association class (p. 198): An AssociationClass is a declaration of an Association that has a set of Features of its own. An AssociationClass is both an Association and a Class, and preserves the static and dynamic semantics of both. An AssociationClass describes a set of objects that each share the same specifications of Features, Constraints, and semantics entailed by the AssociationClass as a kind of Class, and correspond to a unique link instantiating the AssociationClass as a kind of Association.
¶ Both Association and Class are Classifiers and hence have a set of common properties, like being able to have Features, having a name, etc. These properties are multiply inherited from the same construct (Classifier), and are not duplicated. Therefore, an AssociationClass has only one name, and has the set of Features that are defined for Classes and Associations.
(†2486)
