when we model normal application, there are inheritance relationship, for example, in <<Apply UML and pattern>>, there is Payment<-CreditCardPayment Payment<-CashPayment Payment<-CheckPayment how should we model this in our class diagram, should we model in the same way? but actually in J2ee, you won't have CreditCardPaymentEJB， CashPaymentEJB，CheckPaymentEJB， but you only have one EJB that is PaymentEJB because it's correspondent to only one table. In this context, should we show only the payment in the class diagram, if so, how should we show there are different kinds of payment?(just an attribute?) thanks!