| Lesson 7 | Use case associations |
| Objective | Define use case associations and association stereotypes |
So far, we have defined the system, actors, and use cases, but now we need to associate each user with the system features they need to
perform their jobs.
Association notation
Associations are represented by a line connecting an actor to a use case. In some tools an arrow is
drawn from the actor to the use case to indicate that the actor initiates the use case. In the more
recent use case manuals the association is simply a line to show that there is communication between the
two elements. Just remember that the key is to identify what use cases the actors need to access. These
connections will form the basis for the interfaces of the system and subsequent modeling efforts.
Delegation
Sometimes one use case may need to ask for help from another use case. For example, use cases titled
Deposit Money and Withdraw Money might not actually update a bank account. They delegate the changes to
an existing use case, Update Account.
When one use case delegates to another, the association is drawn as a dashed arrow from the "using" use case to the "used" use case and labeled with the <<Uses>> stereotype notation.
When one use case delegates to another, the association is drawn as a dashed arrow from the "using" use case to the "used" use case and labeled with the <<Uses>> stereotype notation.
The stereotype notation is used throughout the UML, most commonly on use case associations and on
classes. The standard notation is to enclose the word in guillemets << >> (French
quote marks). Stereotypes provide a means to extend the UML without modifying it. A stereotype functions
as a qualifier on a model element, providing more information about the role of the element without
dictating its implementation.
Special caseTo indicate that a use case is a special case of or a variation on another use case, draw the dashed arrow from the special case to the general case and label the line with the <<Extends>> stereotype notation.
Step through the process of adding associations and association stereotypes to the use case diagram:
In the next lesson, you'll learn to build a use case diagram based on user interviews.
Usecase Association - Quiz
Click the Quiz link below to test your knowledge of the use case diagram notation.
Usecase Association - Quiz
Usecase Association - Quiz
