Section 2.3. Use Case Overview Diagrams

2.3. Use Case Overview Diagrams

When you are trying to understand a system, it is sometimes useful to get a glimpse of the context within which it sits. For this purpose, UML provides the Use Case Overview diagram. Use Case Overview diagrams give you an opportunity to paint a broad picture of your system's context or domain (see Figure 2-16 for an example).

Figure 2-16. The CMS's context as shown on a Use Case Overview diagram

Unfortunately, Use Case Overviews are badly named as they don't usually contain any use cases. The use cases are not shown because the overview is designed to provide a context to your system; the system's internalscaptured by use casesare not normally visible.

Use Case Overviews are a useful place to show any extra snippets of information when understanding your system's place within the world. Those snippets often include relationships and communication lines between actors. These contextual pieces of information do not usually contain a great deal of detail, they are more a placeholder and starting point to for the rest of your model's detail.