I will start by trying to identify some possible fortresses. Because customers will be using browsers, I know that I will have at least one presentation fortress. Vendors will be coming into my system programmatically, so I know I will need a Web service fortress. I also know that I will have at least one business application fortress to process the requests. So far, I am up to three fortresses. But how many business application fortresses should I have? And what about treaty management and service fortresses?
Let me start by identifying the functionality that I think needs to be in the system someplace:
Customer gateway: sending catalog information, accepting browser requests, and preparing the order information