Artifact: Actor |
This artifact represents a set of roles interacting with a system. An instance can be an individual or an external system.
Domain: Requirements Work Product Kinds: Model Element
Purpose
Different Stakeholders use this artifact for different purposes: Analysts use this artifact to define the system boundaries, identify external interfaces, and describe Use Cases interactions with Actors. Developers use this artifact to capture characteristics of human Actors when they are creating the user interface and to realize Use Cases (in terms of objects) and their interaction with Actors.
Relationships
Container Artifact | Use Case Model
Roles | Responsible: Analyst | Modified By: Analyst
Tasks | Input To: | Output From: Detail Requirements Find and Outline Requirements
Description
Main Description | To fully understand the system's purpose, you must know who the system is for, that is: Who will use the system? Actors represent different types of users. An actor is anyone or anything that exchanges data with the system. Therefore, an actor can be a user, external hardware, or another system. The difference between an actor and an individual system user is that an actor represents a particular class of users, rather than an actual user. Several users can play the same role, which means that they can be the same, single actor. In that case, each individual user constitutes an instance of the actor. As an illustration, Ivar and Mark are operators of a recycling machine. When they are using the machine, each is represented by an instance of the actor called Operator. However, in some situations, only one person plays the role modeled by an actor. For example, there may be only one individual in the role of system administrator for a rather small system. The same user can also act as several actors (that is, the same person can take on different roles). Charlie uses the Depot-Handling System primarily as Depot Manager, but sometimes he also uses the Depot-Handling System as an ordinary Depot Staff member. For each Actor identified, document the name and brief description. It is also necessary to capture the Use Cases that this Actor initiates and those in which the Actor plays a secondary role.
Tailoring
Impact of not having | If you do not use this artifact, important Stakeholder perspectives may not be taken into account. This will result in a solution that does not meet all users' needs. It will be very difficult, if not impossible, to assess the completeness of the set of Use Cases without the context provided by the associated Actors.
Representation Options | If your project is using a Use Case model, there is no need for a separate representation for Actors other than in the Use Case model and in the Use Case specification. The simplest method is to capture the Actor's name and a its brief description in a table. Include a list of the Use Cases that this Actor initiates, as well as the Use Cases in which the actor participates in a secondary role. See the discussion of the Actor-Goal-List in Guideline: Use Case Formats for more information on this representation option.
More Information
Checklists | Actor
Guidelines | Find and Outline Actors and Use Cases Use Case Formats
This program and the accompanying materials are made available under the Eclipse Public License v1.0 which accompanies this distribution. View copyright information here: OpenUP Copyright