Review Statechart Notation

The Statechart notation in UML (Unified Modeling Language) is designed to provide a powerful means of visualizing the dynamic behavior of an individual class or a collaboration of classes through states and transitions. Statecharts are particularly useful in modeling reactive objects, whose states are triggered by specific events. Here's an overview of the purpose and function of the Statechart notation in UML:
Purpose

1. Behavioral Modeling: Statecharts are primarily used to model the behavior of a system, focusing on how an object responds to various events by changing states.
2. Event-Driven Systems: They are particularly suited for event-driven systems where an object's state is changed by external or internal events.
3. Complex Control Logic: Statecharts help in understanding and managing complex control logic that would be difficult to grasp with traditional flowcharts or sequence diagrams.
4. Specification of Reactive Systems: They are ideal for specifying the reactive and responsive nature of a system where the timing and sequence of events are crucial.

Function

1. States: A Statechart diagram represents states of an object and the transitions between these states. A state is a condition during the life of an object during which it satisfies some condition, performs some activity, or waits for an event.
2. Transitions: Transitions show how the state of an object changes from one to another. A transition is triggered by an event and can be constrained by conditions, leading to a change in state.
3. Events: Events are external inputs that affect the system and can trigger state transitions. These can be signals, time events, changes in condition, or invocations of operations.
4. Actions: Actions are activities that are executed as a result of a transition. They can be associated with entering or leaving a state or with the transition itself.
5. Entry/Exit Actions: Statecharts can specify actions that occur upon entering or exiting a state, allowing for more precise control over object behavior.
6. Hierarchical States: Statecharts support hierarchical states (or nested states), enabling a high-level state to be broken down into finer-grained substates, which simplifies complex state behavior by reusing parts of the model.
7. Concurrent States: They can also model concurrent states within an object, representing independent regions of states that can operate concurrently, which is useful for modeling objects that can be in multiple states at the same time.

Overall, the Statechart notation in UML is a sophisticated tool for modeling dynamic behaviors and interactions within systems, making it easier for developers and designers to conceptualize and communicate complex state-dependent behaviors and conditions.

The statechart notation is fully described in the diagram below.

Review it as needed so that you can proceed with the remaining content of this module. Please pay close attention to the method used to derive a statechart from a set of sequence diagrams. This technique will be the focus of the exercise for this lesson.

In the following example we help you start the construction of a statechart diagram using a sequence diagram as your source. In mechanics rather than the complexity of the problem domain. But the same strategy can be employed as the problem domain increases in complexity.

Click the Exercise link below to work on the course project. In this exercise you will build the statechart for the ShowSeat object.
State Chart Notation - Exercise