Modeling Dynamic Behavior

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Use cases and scenarios provide a way to describe system behavior; that is, the interaction between objects in the system. Sometimes it is necessary to look at the behavior inside an object. A statechart diagram shows the states of a single object, the events or messages that cause a transition from one state to another, and the actions that result from a state change.

A statechart diagram will not be created for every class in the system, only for classes with "significant" dynamic behavior. Interaction diagrams can be studied to determine the dynamic objects in the systemones receiving and sending many messages. Statechart diagrams are also useful to investigate the behavior of an aggregate "whole" class and of control classes.

Care must be taken to stay in an analysis frame of mind concentrating on the WHAT of the problem and not the HOW of the solution.

CREATING STATECHART DIAGRAMS IN RATIONAL ROSE

1. Right-click to select the class in the browser and make the shortcut menu visible.

2. Select the New:Statechart Diagram menu choice. This will add a state diagram called NewDiagram to the browser.

3. While the diagram is still selected, enter the name of the diagram.

4. To open the diagram, click the + to expand the class in the browser, click the + to expand the State/Activity Model in the browser and double-click on the statechartdiagram in the browser.

The browser view of the statechart diagram for the CourseOffering class is shown in Figure 9-1.

Figure 9-1. Statechart Diagram in the Browser

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