• What steps are involved in working with the IT system? To answer this question we have to observe the actor's work with the IT system. What does the actor do with the IT system? What does he or she enter? What does the IT system display? What does the interaction look like? Here, it is important to find the appropriate level of detail. Not every key pressed makes up a work step. The next two questions will help you find the appropriate level of detail. The information from the use case diagram is not sufficient to understand use cases. The flow of interaction that stands behind a use case has to be described. In addition to purely verbal description, description in a use case sequence diagram has proven to be especially valuable. We can ask the following questions when developing a use case sequence diagram for the use case