Learning UML

Chapter 8. Activity Diagrams

This chapter focuses on activity diagrams, which depict the activities and responsibilities of elements that make up a system. First, I introduce activity diagrams and how they are used. Next, I discuss action states and their details. Finally, I go over flows and their details. Many details of activity diagrams that were not fleshed out in Chapter 2 are more fully elaborated here, and throughout the chapter, I include suggestions relating to activity diagrams.

Activity modeling is a specialized type of behavioral modeling concerned with modeling the activities and responsibilities of elements. You usually apply activity modeling in conjunction with sequence and collaboration modeling (Chapter 6) to explore the activities and responsibilities of interacting and collaborating elements.

Action States

As discussed in Chapter 2, as elements communicate with one another within a society of objects, each element has the responsibility of appropriately reacting to the communications it receives. An action state represents processing as an element fulfills a responsibility. There are various types of action states, including simple, initial, and final action states. The next few sections discuss these different types of action states.

Simple Action States

A simple action state represents processing. For example, the project management system may have the following simple action states:

Project Manager Enters Report Criteria

Indicates that the project manager enters ...