Statechart diagrams Collaboration diagrams. Defining Use Cases and Use Case Diagrams A use case scenario is a description, typically written in structured English or point form, of a potential business situation that an application may or may not be able to handle. An Example of a Use Case Diagram To put your use cases into context, you can draw a use case diagram, as shown in Figure 1. Use case diagrams are straightforward, showing the actors, the use cases with which they're involved, and the boundary of the application. An actor is any person, organization, or system that interacts with the application but is external to it.
Actors are shown as stick figures, use cases are ovals, and the system is a box.
In this example, students are enrolling in courses via the help of registrars. Note how for some use cases, more than one actor is involved, and that sometimes the flow of information is in only one direction. The combination of use cases and their corresponding use case diagram is referred to as a use case model. Use case models are often accompanied by a glossary describing the terminology used within them. The glossary and use case model are important inputs for the development of class diagrams.