definition of the sequence of action s a system performs that yields an observable result of value to a part icular actor. A use-case class contains all main, alternate flows of event s related to producing the "observable result of value". [D04892] RUP
A task that is part of the business process, for example, renewing insurance policies in an insurance application.
A use-case model consists of actors, use cases, and relations among them. Actors represent everything that must exchange information with the system, including what are typically called users. When an actor uses the system, the system performs a use case. A good use case is a sequence of transactions that yields a measurable result of value for an actor. The collection of use cases is the system's complete functionality. [go to site
(class) A description of system behaviour, in terms of sequences of actions. A use case should yield an observable result of value to an actor. A use case contains all alternate flows of events related to producing the "observable result of value". More formally, a use case defines a set of use-case instances or scenarios. The specification of a sequence of actions, including variants, that a system (or other entity) can perform, interacting with actors of the system. See use-case instances.