It seems as if Use Cases are too obvious to mention, but with the great amount of mystery surrounding these deliverables, I feel the need to mention a few definitions. First of all, a Use Case can be text or graphical, as in a state diagram. The basic attributes involve identifying the user intention and the system responsibility. More complexity is added as you consider the relationships between objects, the preconditions, the post-conditions, and the business rules. Therefore, a Use Case can come in different flavors. I have a graphical one below, roughly based on a decision-reaction flavor. Depending on your point of view, they may also be confused with taskflows, scenarios, etc. The information represented in each of these does involve a certain amount of overlap, but depending on the project they may not all be necessarily included.