UML Weekend Crash Course™ - To Parent Directory

244
Sunday Morning
REVIEW
The Sequence diagram provides the events that can affect an object’s condition. It also
helps to identify the periods of time between the changes caused by the events. These
periods of time when the object remains unchanged may represent states on the Statechart
diagram.
To derive the Statechart from the Sequence diagrams, use the following steps:
1. Identify the events directed at the lifeline of the object you’re modeling.
2. Identify candidate states by isolating the portions of the lifeline between the
incoming events.
3. Name the candidate states using adjectives that describe the condition of the
object during the period of time represented by the gap.
4. Add the new states and events to the Statechart diagram.
Remember that the scope of the Sequence diagram is only one scenario. The scope of the
Statechart diagram is the entire life of the object, so it may take many Sequence diagrams
to build one Statechart.
QUIZ YOURSELF
1. On a Sequence diagram, which events may change an object (See “Deriving a
Statechart from Sequence Diagrams.”)
2. How do you identify a candidate state on a Sequence diagram (See “Deriving a
Statechart from Sequence Diagrams.”)
3. If an event on the Sequence diagram causes a change to the object, how do you
model it on the Statechart diagram (See “Deriving a Statechart from Sequence
Diagrams.”)
4. What do you do if an event does not cause a change in the object it is directed at
(See “Deriving a Statechart from Sequence Diagrams.”)
5. What kind of word is good for naming a state (See “Deriving a Statechart from
Sequence Diagrams.”)