A diagram showing a Conceptual Data Model is available.

Requirement : To create a contact database for tracking, among other things, tenants for rental units.
Each contact could have several current addresses and several current phone numbers.

From time to time, a contact could change some piece of information, such as their name (get married),
an address, or a phone number.
A range of Enquiries must be supported.
A history must be maintained to look up old information, and track down old Tenants.
An audit trail should be provided to track when a change was made and by whom.