Lab $4$: UML: Use Case Diagram$$A use case diagram defines the primary requirements of a system. It shows works completed by the actors of a system.$$Use Case: Graphically depicts the interactions among elements of a system$$Use Case Names begin with a verb $$ A use case models an action, so the name should begin witha verb. It should follow a Verb$+$Noun format.$$Make the name descriptive $$ This gives more information to others looking at the diagram. Forexample, "Print an Invoice after purchase" is better than "Print an Invoice."$$Use Case Diagram models real$-$world objects and functionalities by listing steps that a system needs to follow and identify shall $($mandatory$)$ and should $($non$-$mandatory$)$ requirements. The following link describes the Use Case diagrams in detail: