Artifacts > Requirements Artifact Set > Use-Case Model... > Actor


An actor defines a coherent set of roles that users of the system can play when interacting with it. An actor instance can be played by either an individual or an external system.
UML representation: Actor
Role: System Analyst
Sample Reports:
More information:

Input to Activities: Output from Activities:

Purpose To top of page

Different stakeholders use this artifact for different purposes:

  • System analysts — to define the system boundaries.
  • User-interface designers — to capture characteristics on human actors.
  • Use-case authors — to describe use cases and their interaction with actors.
  • Object analysts — to realize use cases and their interaction with actors.

Properties To top of page

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, and so on. 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 To top of page

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 To top of page

The system analyst is ultimately responsible for managing the actors. Although both requirement specifier and user-interface designer roles will update the detailed information about each actor, the system analyst is responsible for ensuring that:

  • Each actor has the correct communicates-associations with the use cases with which it participates.
  • Each actor is part of the correct generalization relationships.
  • Each actor defines a cohesive role and is independent of other actors.

A user-interface designer is responsible for the integrity of human actor details, ensuring that:

  • Each actor captures the necessary characteristics required to build the user interface.
  • The local use-case diagrams describing the actor are readable and consistent with the other properties.

Tailoring To top of page

Decide which properties to use and how to use them. In particular, you need to decide at which level of detail the “Characteristics” property needs to be described.

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