UML Weekend Crash Course™ - To Parent Directory

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Saturday Evening
When the current condition, or state, of the account is overdrawn, the account will
respond differently than when the account is in the open condition — checks will be
rejected rather than paid or the bank will cover the check and charge you an exorbitant
fee for its kindness.
Tip
The Statechart has been around a long time. You may know it by the name
state diagram, state machines, or state transition diagram.
Next, contrast the scope of the Statechart with that of the Sequence diagram. The scope
of the Statechart is the entire life of an object. The scope of the Sequence diagram is a single
scenario. Consequently, it is possible to derive a Statechart from the set of Sequence
diagrams that use the object.
The Statechart models the events that trigger a transition (change) from one state to
another state. Each event may have a corresponding action that makes the changes in the
object (that is, alters the attribute values). While an object is in a state, it may also perform
work associated with that state. Such work is called an activity.
The Statechart can also be used to model concurrent activities within a state by creating
parallel substates within a superstate. Using the substate and superstate notation, you can
explicitly identify split and merge of control for concurrency.
Defining the Fundamental Notation for a Statechart Diagram
The foundation for the Statechart is the relationship between states and events. The following
examples illustrate the Statechart notation using the Order object. A state is modeled as
a rounded rectangle with the state name inside, as in Figure 20-1, much like the short form
of the class icon, where only the name compartment is visible.
Filled
Figure 20-1 State symbol with only name compartment shown (minimum
configuration)
The initial state of an object has its own unique notation, a solid dot with an arrow
pointing to the first state. The initial state indicates the state in which an object is created
or constructed. You would read Figure 20-2 to say, “An Order begins in the ‘Placed’ state.” In
other words, the Order comes into existence when a customer places it.
Placed
Figure 20-2
The initial state notation