Most of what I would want to say has already been said above by tye.

However I have one point he missed.

You talk a lot about what you are going to do. You will store objects in a database. You will have these amazing general objects as soon as you figure out how to design them. And so on.

But you haven't said why you are doing it. What is your actual task? What do you need to do? Have you tried thinking how to design an actual application and then walked through on paper how it would function? A good exercise is to have a group of people stand around with a ball. Each person is an object, and they throw the ball around as they call methods on each other. Have you tried that?

My point is that in the abstract we tend to build castles in the sky and get into binds. A good antidote for this is to attempt to experience the practical details as directly as possible. Based on how vague and general your classes currently look, I suspect you may need some of this antidote...