The use case diagram shows the functionality of the system from an outside-in viewpoint.

	Actors (stick men) are anything outside the system that interacts with the system.
	Use Cases (ovals) are the procedures by which the actors interact with the system.
	Solid lines indicate which actors interact with the system as part of which procedures.
	Dashed lines show dependencies between use cases, where one use case is 'included' in or 'extends' another.