Like learning to ride a bicycle

Learning this technique has a bit in common with learning to ride a bicycle. Until you "get it", robustness analysis can seem devilishly difficult, but once you do get it, it's really very simple.

To jump-start your understanding, we'll walk through plenty of examples in this chapter. Experience has shown us that you usually need to draw six or so robustness diagrams before the penny drops and you suddenly get it. Just remember, a robustness diagram is an object picture of a use case.

Once you get the hang of it, you should be able to rattle off a robustness diagram in about 10 minutes (or less) for each use case. Actually, as you'll see, the trick is in writing your use case correctly. If a robustness diagram takes more than 10 minutes to draw, you can bet you're spending most of that time rewriting your use case text.

Updating your domain (static) model

Our next diagram shows the updated static model for the internet bookstore we are building, following robustness analysis for the "Show Book Details" and "Write Customer Review" use cases. The added or updated classes are shown in red.

Static model for the internet bookstore, after robustness analysis for two use cases