The first goal of data modeling is to achieve completeness in covering the requirements of an application. However, this doesn't mean that we need all of the requirements of an application upfront when we start the data modeling, which adopts more of a waterfall way. The data models we design should be able to support the implementing of the features specified in the requirements that are currently available.

And, it also means that during data modeling, we should include those business rules that need to be applied to the database level so that we can be confident with the stored data.