Should have looked at the diagram to get those neurons firing again.
The generalization is "more like" inheritance. The parent captures the commonality of the children - the parent could be abstract. Each child is a full description of a use case.
An extend is more like a "plugin" or "module" that plugs into the extension points of the base use case. So to get the full extended use case you have to look at "base + extend". The base case can specify multiple extension point names - the extension can then insert segments into these extension point to modify the behavior of the base case.
Then there is also the "include" which typically is a fragment can be shared between multiple use cases.
Agile Modeling: Use Case Reuse Frankly, use case diagrams are of limited usefulness � they just serve as an overall map of your use cases.
UML for Java� Programmers (
amazon US) p.66:
Of all the diagrams in UML, use case diagrams are the most confusing, and the least useful. With the exception of the system boundary diagram, which I�ll describe in a minute, I recommend that you avoid the them entirely.
If you have to expend any effort on use cases (instead of
User Stories)
you should focus on the text-based use cases:
Alistair Cockburn: Use case fundamentals Alistair Cockburn: Structuring use cases with goals Writing Effective Use Cases (
amazon US).
Unfortunately text-based use cases aren�t as pretty as use case diagrams
[ September 25, 2007: Message edited by: Peer Reynders ]