I am just in the first phase of preparation. I have just read Mark Cade's book and I am quite delighted. I have a little doubt about correctness of class diagram on page 169. There is a relationship between order and lineitem. It is clear and logical. An order has many line items. But what about relationship between product and lineitem. I think there should be * close to lineitem in relationship with product. Product can be present in more than on line item. I can be wrong. I have not yet revised my UML knowledge. Thank you very much for any answer.