Executable UML: A Foundation for Model-Driven Architecture

9.3. State Transition Table

Examination of the statechart diagram for the microwave oven reveals that the model fails to answer certain important questions:

• What happens if we press the button when cooking is complete?

• What happens if we press the button while cooking?

• What happens if we press the button when the door is open?

• Can we close the door when the door is already closed? (Put another way: What happens if we detect the doorClosed event when the door is already closed?)

The statechart diagram shows a set of states, events, and transitions, but the diagram cannot cover all possible combinations. In this section, we'll use an alternative representation^[2] of a state machine—the state transition table (STT)—to ensure completeness of the underlying ...