1. Use Case A use case specifies the behavior of a system or a part of a system and is a description of a set of sequences of actions, including variants, that a system performs to yield an observable result of value to an actor.

2. Use case Actors: can be human or automated systems A use case describes what a system does but it does not specify how it does it.

3. Sample Use Case 1. Use Case NameLogin DescriptionUser logs into the HACS system ActorCan be cell phone User, laptop User, and PDA User, etc. PreconditionThe system is on Basic flow of events 1.The system prompts the User enters username and password 2.The User enters username and password 3.The system validates the entered username and password 4.The system logs the User into the system Alternative flow of events If the User enters an invalid username and password pair, the use case restarts PostconditionUser enters correct username and password Special requirements Interface exists to allow connection between the User’s remote device and the system

4. Reference Class note: Module 14 Textbook: The Unified Modeling Language User Guide, chapter 16, page 223-224