What is Use Case Modeling?
The use case model shows the view of a system from the user's perspective, thus describing what a system does without describing how it does it. The most important role of the use case model is to provide a vehicle for customers or end users and developers to discuss the functionality and behavior of the system.
What is a Use Case?
Use cases model a dialogue between an actor and the system. They represent the functionality provided by the system; that is, what capabilities will be provided to an actor by the system.
The formal definition for a use case is:
A use case is a sequence of transactions performed by a system that yields a measurable result of values for a particular actor.
What is a Use Case Diagram?
A use case diagram is a graphical view of some or all of the actors, use cases, and their interactions identified for a system. Each system typically has a Main Use Case diagram, which is a picture of the system boundary (actors) and the major functionality provided by the system (use cases).