Sequence diagrams

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Sequence diagrams

G. Falquet, L. Nerima
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Objectives

• To show object interactions arranged in time
  sequence
• To show messages exchanged

objects messages
time
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Example message window
active objects
obj1 messageManager
create()
obj2 msgWindow
writeMessage()
buttonClicked()
btnOK readUserInput()
close()
X
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Active and passive objects

• An active object owns a thread of control (path
  of execution)
• A passive object does not have its own thread of
  control
• operations execute under a control thread of an
  active object
• activation execution of an operation

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Procedural flow of control
passive object
obj3
obj2
obj1
operationX()
activation
operationY()
return
operationZ()
return
return
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Concurrent threads of control
obj3
obj2
obj1
opA()
fork threads
opB()
join threads
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Showing state changes
obj3resInterface
obj2Book
obj1
return()
available
reserve()
reserved