B Use Case Modelling

USE CASE MODELLING

• Definition: Involves the use of use cases, relationships, and actors to analyze system functionality.

PURPOSE OF USE CASE MODEL

• Objectives:

  • Develop the right system.

  • Ensure user requirements are met.

• Use Case Modeling:

  • Effective technique for capturing and documenting user requirements.

USE CASE MODELLING PROCESS

• Captures user requirements effectively.

• Documented in both pictorial and textual formats.

CONCEPTS IN USE CASE MODELLING

• Elements:

  • Use Case Diagram, Actor, Use Case, and Relationship.

USE CASE DIAGRAM

• Composition:

  • Consists of use cases, actors, and relationships between them.

• Purpose:

  • Visual representation of system functionalities.

  • Defines the scope of the system to be built.

EXAMPLE USE CASE DIAGRAM (BRANCH OFFICER)

• Use Cases Involved:

  • Create Member

  • Delete Member

  • Renew Member

  • Rent Out Car

  • Manage Member Details

  • Print Log

  • Return Car

EXAMPLE USE CASE DIAGRAM (SYSTEM MONITOR)

• Use Case Involved:

  • Print Reminder.

ACTOR TYPES

• Users of the System:

  • Defined by their roles, e.g., not by names.

  • Examples include:

    • Branch Officer

    • Administrator

• Other Systems:

  • Can interact with the system built.

• Devices:

  • E.g., Camera, Barcode Scanner.

• Time:

  • Time can also be considered an actor.

USE CASE

• Represents a functionality from users’ perspectives.

• Key Inquiry:

  • What information must the system maintain?

• Examples of Use Cases:

  • Maintain rental limits, member information.

• Naming Convention:

  • Use verb-noun format, e.g., "Rent Out Car."

USE CASE SPECIFICATION FORMAT

• Components:

  • Flow of Events:

    • Expected Flow

    • Alternate Flow

    • Error Flow

  • Preconditions and Postconditions.

USE CASE SPECIFICATION EXAMPLE: Rent Out Car

• Brief Description:

  • To allow branch officers to process rental transactions.

• Actor:

  • Branch Officer

• Preconditions:

  • Successful login; only members can rent cars.

• Post Conditions:

  • Rented car becomes unavailable.

• Expected Flow:

  • Begins when a member requests a rental.

• Alternate Flow A1:

  • Invalid member identifier prompts an error.

• Error Flow E1:

  • Credit system is inaccessible.

RELATIONSHIPS IN USE CASE MODELLING

• Include Relationship:

  • A mandatory use case must be called by another use case when activated.

• Extend Relationship:

  • An optional use case may be called by another use case when activated.

  • Direction of the arrow indicates the calling use case (unlike the "include" relationship).

• Generalization Relationship:

  • Involves inheritances such as validating different IDs (member, car).

USE CASE DIAGRAM WITH INCLUDE + EXTEND

• Use cases interconnected including:

  • Delete Member

  • Create Member

  • Branch Officer activities.

USE CASE DIAGRAM WITH GENERALIZATION

• Illustration of Generalization:

  • Branch Officer interactions with various use cases including:

    • Delete Member

    • Renew Member

    • Validate Member ID, etc.