4.1. Basics of Use Cases

Systems respond to external signals by carrying out some desired activity, often with varying outcomes depending upon the system's state. Each desired activity is a functional requirement, such as:

  • A customer can order a book by selecting a book number and quantity.

  • A customer checks out an open order by entering the credit card number and shipping information.

  • The credit card company approves or declines a charge.

  • If the customer's credit card charge is approved, the requested items are packed and shipped to the customer.

Use cases are a tool for organizing system requirements by understanding the interactions between the actors that make a request and the responses, or activities, made by the system. (These terms were ...

Get Executable UML: A Foundation for Model-Driven Architecture now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.