Rational Rose Lab Topic 1

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Rational Rose Lab Topic 1

• Use Case Model

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What is a Use Case model?

• Use Case is a model of what the system is
  supposed to do (use cases), and the systems
  surrounding (actors).
• It models the dialogue between the actor and the
  system.
• It represents the functionality provided by the
  system to the actors.

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Definition of Use Case

• The classic definition of Use case comes from
  Ivar Jacobsons Object-Oriented Software
  Engineering (OOSE) which states
• A Use Case is a sequence of transactions in a
  system
• whose task is to yield a measurable value to an
  individual
• actor of the system.
• A use case is a sequence of transactions through
  the system, that is, an instance
• An actor is a role that someone or something in
  the environment can play in relation to the
  business.

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Actors

• Actors are not part of the system, they represent
  anyone or anything that must interact with the
  system.
• An actor may actively interchange information
  with the system.
• An actor may be passively receiving information
  from the system.
• An actor can represent a human, a machine or
  another system.

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Finding Actors Useful Questions

• Who is interested in a certain requirement?
• Where in the organisation is the system used?
• Who will supply the system with this information,
  use this information and remove this information?
• Who will user this particular function in the
  system?
• Who will support and maintain the system?
• Any external system resource?
• What actors do this use case needs?
• Does one actor play several different roles? Or
  do several actors play the same role?

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Types of Actors

• Primary Actors
• Active
• Initiate activity with the system
• Usually will get some value in return
• Example Payroll clerk, Student, Bank Customer
• Secondary Actors
• They are passive
• Do not initiate any activity with the system
• Usually machine or other system
• Are there to ultimately fulfill the needs of the
  primary actor
• Example Bank System, Printer, Application

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Rational Rose step by step

• To create an actor in the Browser
• 1. Right click on the Use Case View to make the
  pop-up menu visible.
• 2. Select the NewActor menu choice. This will
  add a new actor called NewClass to the Browser.
• 3. While the new actor is still selected, enter
  its name.

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Actor Documentation

• A brief description for each actor should be
  added to the model
• The description should identify the role the
  actor plays while interacting with the system.
• For example, the actors description in the Course
  Registration System
• Student a person who is registered to take
  classes at the University
• Lecturer a person who is certified to teach
  classes at the University
• Registrar - the person who is responsible for
  maintaining the Course Registration System.
• Billing System the external system responsible
  for student billing

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Rational Rose step by step

• To make the Documentation window
  visible/invisible
• 1. Select the ViewDocumentation menu choice to
  toggle the selection (? for visible).
• Documenting Actors in Rational Rose
• 1. Click to select the specific actor in the
  Browser.
• 2. Position the cursor in the documentation
  window and enter documentation.
• OR
• 1. Right click on the specific actor in the
  Browser to make the pop-up menu visible.
• 2. Select the Open Specification option.
• 3. Select the General tab.
• 4. Position the cursor in the documentation field
  and enter documentation.

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Use Case

• A use case models a dialogue between actors and
  the system
• A use case is initiated by an actor to invoke a
  certain function in the system
• A use case is a complete and has a meaningful
  flow of events
• Taken together, all use cases constitute for all
  possible ways of using the system

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Finding Use Case Useful Questions

• What are the task of each actors?
• Will any actor create, store, change, remove. Or
  read information in the system?
• What use cases will create, store, change,
  remove, or read this information?
• Will any actor need to inform the system about
  sudden, external changes?
• Does any actor need to be informed about certain
  occurrences of the system?
• What use case will support and maintain the use
  case?
• Can all functional requirements be performed by
  the use case?

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Rational Rose step by step

• To create a use case in the Browser
• 1. Right click on the Use Case View to make the
  pop-up menu visible.
• 2. Select the NewUse Case menu choice. This will
  add a new unnamed use case to the Browser.
• 3. While the new use case is still selected,
  enter its name.

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Basic Use Case Diagram

• Use case diagram is created to visualise the
  interaction between the actors and use cases.

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Rational Rose step by step

• To open the Main Use Case diagram
• 1. Click on the sign on the Use Case View in
  the Browser to expand the tree
• 2. Double click on the Main use case diagram to
  open the diagram.
• To create a new Use Case Diagram
• 1. Right click on the Use Case View in the
  Browser to make the pop-up menu visible
• 2. Select the NewUse Case Diagram menu option.
• 3. While the new use case diagram is still
  selected, enter the name of the diagram.
• 4. Double click on the diagram in the Browser to
  open the diagram.

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Example Course Registration Use Case Diagram
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Rational Rose step by step

• To add Actors and Use cases to Use Case Diagrams
• 1. Click to select the actor or use case in the
  Browser.
• 2. Drag the icon to the Use Case Diagram.
• To create new actors or uses cases on the
  diagram
• 1. Click to select the Actor icon or the Use Case
  icon on the toolbar.
• 2. Click on the diagram to place the Actor or Use
  Case.
• 3. While the Actor or Use Case is still selected,
  enter its name.
• Note Actors and Use Cases created in this
  manner are automatically added to the Browser.

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Rational Rose step by step

• To create a relationship in the Use Case Diagram
• 1. Click to select the Unidirectional Association
  icon on the toolbar (if the icon is not
  available, tailor to toolbar to include the icon)
• 2. Click to select the actor or use case
  initiating the communication.
• 3. Drag the relationship to the other actor
  involved in the communication.

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Exercise 1

• From the ATM case study,
• identify the actors
• identify the use cases
• draw the use case diagram
• save your rational model