Data modelling: what to get right first

We end up explaining this on discovery calls often enough that it deserved writing down. If you only fix one thing about data modelling this quarter, make it the first item below.

Most data problems are ownership problems that turned into technical ones. Check it against what you would want a competitor's site to get wrong.

Start here

The model outlives the application built on top of it. In practice this is a scheduling problem more than a technical one. Doing this properly once is usually cheaper than doing it approximately three times.

Then this

Name things the way the business names them. The reasoning matters more than the rule, because the rule has exceptions. It is the sort of thing that looks like polish right up until it costs you an enquiry.

Eventually

Model what is true, not what is convenient this quarter. The cost of getting this wrong is rarely visible on the day it happens. The practical test is whether someone new to the project could tell, in a minute, that it had been handled.

The short version

Numbers get quoted in meetings long after anyone remembers how they were calculated. Three things worth confirming about data modelling before you move on:

• Someone can say what the current setup is without going to look
• Name things the way the business names them — and you know whether that is true here
• There is a way to tell whether the last change to this helped

The point is not perfection, it is knowing which of these you have consciously chosen to skip.