UML Use Case Diagrams Lecture Notes

Overview

• Objective: Teach UML use case diagrams.
• Structure of Lecture:
  • High-level overview
  • Discussion of systems, actors, use cases, and relationships
  • Building a use case diagram together
  • Examples for in-depth understanding

Use Case Diagrams

• Purpose: Communicate complex ideas simply.
• Description:
  • Shows a system/application.
  • Displays users (actors) interacting with the system.
  • Outlines basic flows of the system's functions.

Creating a Use Case Diagram

• Tools: Recommended to use a diagramming tool (e.g., Lucidchart).

Key Elements of Use Case Diagrams

1. Systems

• Definition: The entity being developed (e.g., app, website).
• Representation: Rectangle with the system name at the top.
  • Example: "Banking App" defines the scope of the application.

2. Actors

• Definition: External entities that interact with the system.
• Representation: Stick figures.
• Types of Actors:
  • Primary Actor: Initiates system use (e.g., Customer).
  • Secondary Actor: Reacts to primary actor's actions (e.g., Bank).
• Placement: Primary actors on the left, secondary on the right.

3. Use Cases

• Definition: Actions performed within the system.
• Representation: Ovals inside the system rectangle.
• Examples for Banking App:
  • Log In
  • Check Balance
  • Transfer Funds
  • Make Payment
• Characteristics:
  • Start with a verb (action-oriented).
  • Be clear and descriptive.
  • Logical ordering is encouraged (e.g., Log In first).

4. Relationships

• Definition: Links between actors and use cases.
• Types of Relationships:
  • Association: Basic interaction between actor and use case.
  • Include: A use case that is dependent on another base use case.
  • Extend: A use case that may occur under certain conditions.
  • Generalization: Inheritance where one use case can have specialized versions.

Example of Relationships

• Include:
  • Log In -> Verify Password (always happens when logging in).
• Extend:
  • Log In -> Display Login Error (occurs only sometimes).
• Generalization:
  • Make Payment can have options for Paying from Checking or Savings accounts.

Additional Concepts

• Use Case with Extension Points: Details of optional flows or actions related to a use case.

Conclusion

• Importance of Simplicity: Even complex systems should be visualized simply.
• Resources: For more examples and diagrams, visit Lucidchart's website.

Additional Notes

• This tutorial provides foundational knowledge for UML use case diagrams, aimed at facilitating clearer communication of system functionalities.