use case diagram for online telephone directory

The context diagram shows only the entities that will interact with the system in some way (either by passing information to it or by receiving information from it). Incidentally, the external entities on the context diagram are also the first draft of the system's actors (identifying each actor is the next step in the use case modeling processes).Įqually important are the entities that do not appear on the diagram. Instead, will use an external payment gateway. In the example above, we can see that building a credit card processing function is out of scope. The context diagram answers the first and most essential question about your requirements: Who needs to use this system? By calling out the things that are external to the system, we define its boundary and scope. Their simplicity helps spread two important pieces of information early in the project. But because they are so easy to create, I prefer to draw them anyhow. This website allows photography enthusiasts to rent expensive camera lenses by the week.Ī context diagram looks so simple that you might be tempted to just skip it. Specifically, note what information is passed and who it is passing it (the system or the entity).īelow is a context diagram example for a fictitious website named.

If it's not obvious why an entity belongs on the diagram, make a note about the interaction between the system and the entity. If it doesn't have a name yet, just label the circle as 'System.' Then list each of the external entities around your system and draw a line between the entity and the system. If your system has a name, use it to label the circle.

a brief note about the interaction between each thing and the system (#3 is optional).īecause it's an overview and lacks much detail, this diagram is an easy way to start building momentum in your requirements gathering process.Ĭreate a context diagram by drawing a circle in the center of the page.the things that need to interact with the system (use case experts call these things external entities), and.the system you're going to be gathering requirements for,.A context diagram is a high-level, informal view of three things: People new to use cases are often unsure of where to start gathering requirements.

Use case diagram for online telephone directory