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Uses Cases

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Uses Cases. Keng Siau. University of Nebraska-Lincoln. Syntax for Use Case Diagram. Actors ... Each use case is a sequence of related transactions performed by ... – PowerPoint PPT presentation

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Title: Uses Cases


1
Uses Cases
  • Keng Siau
  • University of Nebraska-Lincoln

2
Syntax for Use Case Diagram
3
Actors
  • An actor is someone or some thing that must
    interact with the system under development

Student
Registrar
Professor
Billing System
4
Actors
  • An actor represents a coherent set of roles that
    users of use cases play when interacting with the
    use cases
  • Typically, an actor represents a role that a
    human, a hardware device, or even another system
    plays with a system

5
Use Cases
  • A use case is a pattern of behavior the system
    exhibits
  • Each use case is a sequence of related
    transactions performed by an actor and the system
    in a dialogue
  • It describes what a system does but NOT how it
    does it

6
Use Cases
  • A use case is a description of a set of sequences
    of actions, including variants, that a system
    performs to yield an observable result of value
    to an actor
  • Each use case must have a name that distinguishes
    it from other use cases

7
Use Cases
  • Actors are examined to determine their needs
  • Registrar -- maintain the curriculum
  • Professor -- request roster
  • Student -- maintain schedule

Maintain Schedule
Maintain Curriculum
Request Course Roster
8
Use Case Diagram
  • Use case diagrams are created to visualize the
    relationships between actors and use cases

Request Course Roster
Professor
Student
Maintain Schedule
Maintain Curriculum
Registrar
Billing System
9
Use Case Relationships
  • Can organize use cases by specifying
    relationships among them.
  • Generalization
  • Include
  • Extend

10
Use Case Relationships
  • Generalization
  • Child use case inherits the behavior and meaning
    of the parent use case
  • Child use case may add to or override the
    behavior of its parent
  • Child use case may be substituted any place the
    parent use case appears

11
Use Case Relationships
  • Include
  • Base use case explicitly incorporates the
    behavior of another use case at a location
    specified in the base
  • Use an include relationship to avoid describing
    the same flow of events several times
  • by putting the common behavior in a use case of
    its own

12
Use Case Relationships
13
Use Case Relationships
  • Extend
  • An extend relationship between use cases means
    that the base use case implicitly incorporates
    the behavior of another use case at a location
    specified indirectly by the extending use case
  • Use an extend relationship to model the part of a
    use case the user may see as optional system
    behavior

14
Use Case Relationships
Included Use Case
Super Use Case
ltltincludegtgt
ltltextendgtgt
generalization
Extending Use Case
Sub Use Case
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