Object Discovery on the BIll Payment System

I'm developing a bill payment system based on the principles of "Object Thinking" by David West.

I drew up a semantic net based on the domain and covered almost an entire page. I then started writing out CRC cards for the classes in the system and found that many of the classes I had drawn on the semantic net weren't classes at all. Some became part of an object's description (payment schedule, payment rule, website, user name, password). Several were outside of the system (e.g. website to pay bills on, check to mail the creditor).

Since I'm practicing anthropomorphization, I listed each class' motivation on the CRC card. For example a bill wants to pay itself. A creditor wants to be paid the full amount on time. A fund (that keeps track of how much money I have allocated for bill paying) wants to stay in the black.

I was surprised by how my complex semantic net shrunk down to four objects.