>>One other thing I've been confused on: in a current project I'd like to model, >we have an order table, an order line table, a payment table, and a payment >line table. The payment line table refers to the invoice/order. That's four >classes as well, right? with Orders and Payments having collection Properties >containing line items?
>It may be four classes...it may not be. It depends on the entire context of teh application.

Thanks: the following discussion was just what I needed.