Inclusion

A use case can include another use case. If use case A includes use case B, that means use case B is a component of use case A. Please note that it is okay for a use case to be a component in another use case, as long as the included use case is complete by itself and it provides value to at least one actor.

For example, in an airline information system, ``check flight information'' is a valid use case. An end user can simply use the system to check the arrival time of a flight. At the same time, this ``check flight information'' use case can be a component of the use case ``book flight ticket''.