Chapter 8. State Diagrams

State diagrams are a familiar technique to describe the behavior of a system. They describe all of the possible states that a particular object can get into and how the object's state changes as a result of events that reach the object. In most OO techniques, state diagrams are drawn for a single class to show the lifetime behavior of a single object.

There are many forms of state diagrams, each with slightly different semantics. The UML style is based on David Harel's (1987) statechart. Figure 8-1 shows a UML state diagram for an order in the order processing system I introduced earlier in the book. The diagram indicates the various states of an order.

Figure 8-1. State Diagram

Figure 8-1 shows a UML state diagram ...

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