Use Case Development

Develop comprehensive use cases that describe system behavior, user interactions, and business scenarios for clear requirements specification.

When to Use This Skill

• Defining system functionality
• Describing user interactions
• Specifying requirements
• Planning test scenarios
• Communicating with stakeholders
• Designing system behavior
• Creating user documentation
• Estimating development effort

Core Concepts

1. Use Case Structure

**Use Case ID:** UC-001
**Use Case Name:** Process Customer Order
**Actor:** Customer, Sales Rep
**Preconditions:** User is logged in, Items in cart
**Postconditions:** Order created, Payment processed

**Main Success Scenario:**
1. Customer reviews cart
2. Customer proceeds to checkout
3. System validates cart items
4. Customer enters shipping address
5. Customer selects payment method
6. System processes payment
7. System creates order
8. System sends confirmation email

**Alternative Flows:**
3a. Invalid items in cart
  3a1. System removes invalid items
  3a2. System notifies customer
  3a3. Resume at step 1

6a. Payment fails
  6a1. System displays error
  6a2. Customer selects different payment
  6a3. Resume at step 6

**Exception Flows:**
- Network timeout: Save cart, allow retry
- Out of stock: Notify customer, suggest alternatives

2. Use Case Diagram

Actor: Customer
  |
  +-- (Browse Products)
  +-- (Add to Cart)
  +-- (Checkout)
  +-- (Track Order)

Actor: Admin
  |
  +-- (Manage Products)
  +-- (Process Returns)
  +-- (View Reports)

Best Practices

1. Focus on user goals - What user wants to accomplish
2. Be technology-independent - Don't specify UI details
3. Include alternatives - Error cases and variations
4. Keep atomic - One clear goal per use case
5. Define preconditions - Required state before execution
6. Specify postconditions - Expected state after
7. Number steps - Easy reference and traceability
8. Validate with users - Ensure completeness

Resources

• Writing Effective Use Cases: Alistair Cockburn
• UML Use Case Diagrams: OMG specification