Artifact: Actor
Actor |
An actor defines a coherent set of roles that users of the system can play when interacting with it. A user can either be an individual or an external system. |
| UML representation: | Actor |
| Worker: | User-Interface Designer (for human actors) System Analyst (for system actors) |
| Sample Reports: | Report: Actor <actor name> |
| More information: | Guidelines: Actor |
Purpose 
The following people use the actors:
- user-interface designers, when capturing characteristics on human actors;
- system analysts, when finding the system boundaries;
- use-case authors, when describing use cases and their interaction with actors;
- object analysts, when realizing use cases and their interaction with actors;
Properties
Property Name |
Brief Description |
UML Representation |
| Name | The name of the actor. | The attribute "Name" on model element. |
| Brief Description | A brief description of the actor's sphere of responsibility and what the actor needs the system for. | Tagged value, of type "short text". |
| Characteristics | For human actors: The physical environment of the actor, the number of users the actor represents, the actor's level of domain knowledge, the actor's level of computer experience, other applications the actor is using, and other general characteristics such as gender, age, cultural background, etc. | Tagged value, of type "formatted text". |
| Relationships | The relationships, such as actor-generalizations, and communicates-associations, in which the actor participates. | Owned by an enclosing package, via the aggregation "owns". |
| Diagrams | Any diagrams local to the actor, such as use-case diagrams depicting the actor's communicates-associations with use cases. | Owned by an enclosing package, via the aggregation "owns" |
Timing
Actors are found and related to use cases early in the inception phase, when the system is scoped. The characteristics of the actors are described before the user interface is prototyped and implemented.
Responsibility
A user-interface designer is responsible for the integrity of human actors, ensuring that:
- Each actor captures the necessary characteristics required to build the user interface.
- Each actor has the correct communicates-associations with the use cases it participates with.
- Each actor is part of the correct generalization relationships.
- Each actor defines a cohesive role, and is independent of other actors.
- The local use-case diagrams describing the actor are readable and consistent with the other properties.
The system analyst has similar responsibilities for non-human actors, except regarding the characteristics (first bullet above).
