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Use Case Diagrams & Sequence DiagramsSE3A04 – Tutorial
Jason Jaskolka
Department of Computing and SoftwareFaculty of EngineeringMcMaster University
Hamilton, Ontario, [email protected]
October 14/15, 2014
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Outline
1 Use Case Diagrams
2 Sequence Diagrams
3 Questions
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Use Case Diagrams
Definition (Use Case Diagram)
Use case diagrams model the functionality of system using actorsand use cases.
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Use Case DiagramsSystem
Draw your system’s boundaries using a rectangle that containsuse casesPlace actors outside the system’s boundaries
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Use Case DiagramsUse Cases
Draw use cases using ovalsLabel with ovals with verbs that represent the system’sfunctions
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Use Case DiagramsActors
Actors are the users of a systemWhen one system is the actor of another system, label theactor system with the «actor» stereotype
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Use Case DiagramsRelationships
Illustrate relationships between an actor and a use case with asimple lineFor relationships among use cases, use arrows labeled either«uses» (or «includes») or «extends»A «uses» relationship indicates that one use case is neededby another in order to perform a taskAn «extends» relationship indicates alternative options undera certain use case
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Use Case DiagramsRelationships
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Use Case DiagramsExample
ExampleDraw a use case diagram to represent the following system.
Over the summer holiday, university students can book collegehall accommodation online. They must specify their name,student number, course, year, and identify three collegeresidences as their preferences.The system makes an allocation of students to rooms beforethe start of the term, trying, where possible, to allocatestudents to a room in one of their preferred halls.
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Use Case DiagramsExample
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Sequence Diagrams
Definition (Sequence Diagram)
Sequence diagrams describe interactions among classes in termsof an exchange of messages over time.
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Sequence DiagramsClass Roles
Class roles describe the way an object will behave in contextUse the UML object symbol to illustrate class roles, but don’tlist object attributes
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Sequence DiagramsActivation
Activation boxes represent the time an object needs tocomplete a task
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Sequence DiagramsMessages
Messages are arrows that represent communication betweenobjectsUse half-arrowed lines to represent asynchronous messagesAsynchronous messages are sent from an object that willnot wait for a response from the receiver before continuing itstasks
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Sequence DiagramsLifelines
Lifelines are vertical dashed lines that indicate the object’spresence over time
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Sequence DiagramsDestroying Objects
Objects can be terminated early using an arrow labeled«destroy» that points to an ×
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Sequence DiagramsLoops
A repetition or loop within a sequence diagram is depicted asa rectanglePlace the condition for exiting the loop at the bottom leftcorner in square brackets [ ]
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Sequence DiagramsExample
ExampleDraw a sequence diagram representing the process of making aphone call from a cell phone.Hint*: The objects involved include the caller, the phone network,the receiver of the phone call, and the cell phone accountingdepartment.
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Sequence DiagramsExample
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