• Which information is meant to be stored, modified, or deleted in the IT system? If information should be changed, a mutation event is sent to the IT system. 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