Learning UML

Communicate Associations

Figure 4-1 shows actors associated with the project management system and Figure 4-3 shows use cases associated with the project management system, but how are actors and use cases related? A specialized type of association, called a communicate association, addresses the question of how actors and use cases are related and which actors participate in or initiate use cases. (Associations are discussed in Chapter 3.)

As discussed in Chapter 2, a communicate association between an actor and a use case indicates that the actor uses the use case; that is, it indicates that the actor communicates with the system and participates in the use case. A use case may have associations with multiple actors, and an actor may have associations with multiple use cases. A communicate association is shown as a solid-line between an actor and a use case.

Figure 4-4 shows that a project manager participates in managing projects, a resource manager participates in managing resources, and a system administrator and backup system participates in administering the system.

Figure 4-4. Actors and use cases

A navigation arrow on an association pointing toward a use case indicates that the actor initiates the interaction with the system. Figure 4-4 shows that a project manager initiates the interaction with the project management system to manage projects, and a resource manager initiates ...