You should buy Cade's book as it has a good case study. A lot of people have passed by basing their diagrams on Cade's. There's also a good case study in Sun's blueprints ('Pet Store').
Compare Cade's BDOM diagram on page 160 and his Class diagram on page 169. The Class diagram is an extension of the BDOM. In Cade's example class 'Manufacture' in the BDOM is dropped from the Class diagram and becomes an attibute of Product. This is because as you learn more about a project, you make changes. Generally, most classes in the BDOM will end up as entities in an Implementation class diagram, but maybe not all of them. You'll also notice more classes are added to the Class diagram that are not in the BDOM. This could be because they wasn't thought of originally, or they add workflow, or business logic rules (see the session beans Cade added).
In short, you'll get a lot out of Cades case study.
Ray