Our first revision of CRM will start off with a bare bones implementation. It is about as simple as the books application and its data model is illustrated in the next diagram:

The web application will serve a single company and the users are typically the sales representatives and back office employees. In this basic form, an Account is the company we are interested in with a couple of attributes like name and the type of business. We also keep records of Contacts; these are people that may be associated with an Account. These Contacts have attributes like name, gender, and so on. Both Accounts and Contacts may have any number of addresses.