Learning UML

Dependencies

A model may have many use cases, so how do we organize the use cases that define what a system should do? And how do we use this information about use cases to determine how best to execute a project while considering how use cases are related to one another, including what some use cases might have in common, and also taking into account use cases that are options of other use cases? Specialized types of dependencies, called include and extend dependencies, address these questions; dependencies are discussed in Chapter 3. The next few sections discuss these specialized types of dependencies.

Include Dependencies

Perhaps we wish to log the activities of project managers, resources managers, and system administrators as they interact with the project management system. Figure 4-5 elaborates on the use cases in Figure 4-4 to show that the activities of the project manager, resource managers, and system administrators are logged when they are performing the use cases shown in the diagram. Thus, logging activities are common to these three use cases. We can use an include dependency to address this type of situation by factoring out and reusing common behavior from multiple use cases.

Figure 4-5. Use cases with common behavior

An include dependency from one use case (called the base use case) to another use case (called the inclusion use case) indicates that the base use ...