The Scope of a Use Case

However, a use case usually requires a fair amount of additional elaboration, and more work lies ahead. One of these tasks is the decision about whether a set of user interactions is one or several use cases. Consider the use of a recycling machine. The customer inserts cans and bottles into the recycling machine, presses a button, and receives a printed receipt that can be exchanged for money.

Is it one use case to insert a deposit item, another use case to press the button, and yet another to acquire the receipt? Or is this all one use case? Three actions occur, but one without the others is of little value to the customer. The complete process is required to make sense to the customer. Thus, the complete dialogue ”from inserting the first deposit item to pressing the button to getting the receipt ”is a complete instance of use, a use case.

Additionally, you want to keep the three actions together, to be able to review them at the same time, modify them together, test them together, change them together when necessary, write user documentation that describes them, and in general manage them as a unit. This becomes particularly important in larger systems.