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Use Case Diagrams
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Use Case Diagrams

• In order to signify external behavior
• Actors signify functions, that's, a kind of user
  of the system

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Use Case Diagrams

• Use cases signify the sequence associated with
  interaction with regard to a kind of
  functionality, summary associated with scenarios
• The use case model may be the set of all use
  cases. It's a total explanation from the
  functionality of the system and its environment

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Actors

• An actor models an external entity that convey
  using the system
• User
• External system
• Physical environment
• An actor has a unique name as well as an optional
  explanation.
• For Examples
• Passenger A person in the train
• GPS satellite Provides the system along with GPS
  coordinates

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Use Case

• The use case signifies the class of associated
  with functionality supplied by the actual system
  as an event flow.
• The use case includes
• Unique name
• Participating actors
• Entry conditions
• Flow associated with events
• Exit problems
• Unique needs

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Use Case Diagram Example

• Name Purchase ticket
• Participating actor Passenger
• Entry condition
• Passenger standing in front of ticket
  distributor.
• Passenger has sufficient money to purchase
  ticket.
• Exit condition
• Passenger has ticket.

• Event flow
• 1. Passenger selects the number of zones to be
  traveled.
• 2. Distributor displays the amount due.
• 3. Passenger inserts money, of at least the
  amount due.
• 4. Distributor returns change.
• 5. Distributor issues ticket.

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The ltltextendsgtgt Relationship

• ltltextendsgtgt relationships signifies exceptional
  or even seldom invoked cases.
• The exceptional event flows are factored out of
  the main event flow for clarity.
• Use cases signifies exceptional flows can extend
  more than one use case.
• The actual path of theltltextendsgtgt relationship is
  to the extended use case

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The ltltincludesgtgt Relationship

• ltltincludesgtgt relationship signifies behavior
  that's factored from the use case.
• ltltincludesgtgt is actually factored away with
  regard to reuse, not really since it is
  definitely an exception.
• The actual path of the ltltincludesgtgt relationship
  would be to the actual utilizing use case
  (unlike ltltextendsgtgt relationships).

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Use Cases are useful to

• Identifying needs
• New use cases usually create new specifications
  because the system will be assessed as well as
  the layout will take condition.
• Interacting along with customers
• Their notational simplicity can make use case
  diagrams a good way with regard to developers to
  communicate with clients.
• Generating test cases
• The collection of scenarios for a use case may
  suggest a suite associated with test cases for
  those scenarios.

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Use Case Diagrams Summary

• The use case diagrams symbolize external behavior
• The use case diagrams are helpful because an
  index to the use cases
• The use case explanations supply meat associated
  with model, not the use case diagrams.
• All use cases need to being explained for the
  model to be useful.

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