Chapter 17: Interrupting the States by Hosting Events

---

Overview

In This Chapter

• Relating event transitions to class diagrams

• Structuring many events using generalization

• Using different types of events

• Ordering behavior with events

• Using transition icons instead of text

Your objects are constantly interrupted by other objects. Each interruption causes an object to stop what it’s doing, consider the interruption, and then do something as a result of the interruption. In UML, these interruptions are called events. In this chapter we show you the ins and outs of using the different types of events that your objects deal with. You will also see how events on your state diagrams relate to operations on your class diagram. We explain a modeling technique to use when you have too many events. Since state diagrams illustrate flow of control inside your objects, we show you the correct order of execution of event actions and state activities.

 UML2   UML 2 provides you with a new “transition” notation. Because this chapter focuses on the events that interrupt your objects, we show you the new icons UML 2 has for diagramming all the parts of a transition—events, guard conditions, and actions.

---