The traffic light component might have a small set of use cases, as shown in Figure 2. Traffic Light Component Use Cases Figure 2 illustrates the interface of the traffic light component at a high level. This use case diagram is inadequate without a more detailed view, but does serve to highlight the major capabilities of the components. This aspect wouldn t be included in the more detailed view offered by merely listing the operations provided by the component. Simple behavior does not depend upon the component s history.
Continuous behavior depends on the history of the object but does so in a nondiscrete way.
The output depends on the current input and its history. State behavior similarly depends on history, but in a discrete way. An object, when in state X, accepts a particular set of input events, does a particular set of actions and activities, and can reach a particular set of subsequent states. Different states differ in one or more of these three properties. The point is, executables are defined by behavior.