This is the classic use case as described by someone who talks about Software Engineering. All of the training classes (other than Agile classes) that I’ve been to teach formal use case development as a component in a system of requirements management.
The informal use case is the tool of the Agile Requirements Manager. It is a paragraph describing the user’s goals and steps. Also referred to as a basic use case.
We all make mistakes. When we mess up use cases, it is most likely one of these five things.