A requirement arrives in words and leaves as criteria. The same record arriving twice is collapsed, and which copy won is recorded. What arrives is a file whose every column has a written definition.
Null discipline
Keeping empty and unknown distinct, so a filter can tell the difference.
Known-gap register
A written list of what the file does not contain, kept with the file.
Domain attribution
Establishing which web presence belongs to an organisation rather than to its host or its agency.
Write with the criteria you have, however rough, and we will work from there.