What is in a use case diagram?

A use case diagram pictorially illustrate how actors and use cases are related. Use cases are represented by elipses, while actors are represented by match-stick figures.

A ``specialize'' relationship is represented by a solid arrow going from the specific to the general. In other words, the arrow goes from the actor ``CIS Student'' to ``Student''.

An ``association'' relationship is represented by a solid line (no arrow head) between a use case and an actor.

An ``include'' relationship is represented by an arrow of dotted line from the including to the included. There is usually a letter ''i'' on the arrow to indicate this is an inclusion relationship.

An ``extend'' relationship is represented by an arrow of dotted line from the extending to the extended. There is usually a letter ``e'' on the arrow to indicate this is an extension relationship.