Transcript UML Continued

UML
Part 3
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Chapter Ten
State Machine Diagrams
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State Machine Diagrams
• capture the lifecycle and behavior of
objects, subsystems, or systems
• specify the sequence of states an object
goes into, based on responses to events, and
actions the object may perform
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Terminology
• state - condition or situation in the life of an
object determined by attributes
• transition - movement from one state to
another
• event/trigger - an external stimulus that
may cause a transition
• action - some activity that results in a
change of state or a return value
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Thanking
Turning a computer on:
states?
transition?
event?
actions?
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Notation
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Example State Diagram
Actions: “go up”, “go down”, “arrived”, …
State: “On first floor”, Moving up”, “Idle”, …
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Messages between State
Diagrams
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and-substate (concurrency)
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Sequential Substates
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Activity Diagram
• captures actions and their results
• variation of state diagram, but emphasizing
actions
• actions: work and activities to be performed
• results: object-state changes (not the major
point)
• actions may be placed in swimlanes
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Activity Diagram (cont.)
includes:
• how actions are taken
• what they do (activities)
• when they take place (action sequence)
• where they take place (swimlanes)
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Example of a Printing Program
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Another way ...
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Decision Point
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Forks and Joins
•
•
•
•
concurrent or parallel flow of control
synchronization bar
# of forks matches # of joins
activities in parallel flows may use signals
to communicate (such communicating
sequential processes are called co-routines)
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Example
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Swimlanes
(in Activity Diagrams)
• group activities with respect to their
responsibilities
• useful when modeling workflows of
business processes
• specify loci of activities
• every activity belongs to exactly one
swimlane, but transitions may cross lanes
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Example
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Use an activity diagram when
• analyzing a use case
• understanding workflow across many use
cases
• multi-threaded applications
• capturing the work to be performed as an
operation is executing
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Don’t use when...
• trying to see how objects collaborate
(collaborative actions instead of individual
activities); use an interaction diagram
instead
• trying to see how an object behaves over its
lifetime; use a state diagram instead
• modeling a scenario; instead attach it to the
appropriate use case
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