'Required' terminology

In the OMOP CDM documentation for each of the columns it is stated if the column is required or not. Required meaning if it can be left missing or it must be populated.

At the beginning of the documentation it is stated: Similarly, fields that are not required should exist in the CDM table but do not need to be populated.

Although I acknowledge it is stated in the documentation, maybe the word is not the best wording as I've found at least 3 OMOP CDM instances of independent groups that seemed to have misunderstood "required" as if the column must exist. And then they didn't create the columns that have required = No.

Do you think we could find a better word or add a disclaimer in every table (e.g required* and then in the foot note: the column must always exists but if not required it can be left as NULL)? Just to prevent other users to do the same mistake.

Start with the OMOP CDM documentation's introductory definition of “Required” and review the column descriptions and tables that use this terminology. Identify how the wording or a disclaimer can consistently state that every column should exist while non-required columns may be NULL; done means the distinction is clear throughout the affected documentation.