Best Practices in Data Modeling

Two engineers design the same library system. Both models work on the first day.

A year later one of them is easy to change and the other is not. New reports take an afternoon on the first and a week on the second. Nobody can say exactly when the difference appeared.

It appeared in a set of small decisions, made early, that nobody argued about at the time. This lesson lists those decisions and gives the rule for each one.

Understand the requirements before drawing anything

Ask what questions the system must answer, and write them down as a list.