Norm Carr and Tim Meehan have written two nice articles on Use Case diagramming. According to the two authors, Use Cases provide a simple and fast means to decide, specify, and communicate the purpose of a project. Use cases are visual maps of all agreed-upon functionality and can be a powerful tool for controlling the scope of the project.
Links:
- The article Use Cases Part II: Taming Scope

- The article What's the Problem?

Henrik Olsen
- March 08, 2005 - via UI Designer
See also: Use Cases (3)