I recently browsed upon some advanced high level reasoning.
4nf & 5nf.
4th Normal Form and 5th Normal Form.
It basically has to do with relationships between data elements at a higher degree than most typically relationships.
Here's the link I referenced to get a brief understanding:
I don't pretend to be an expert on this subject, however, I'm surprised I never had much interaction with it prior.
If you can make sense of it in simple terms, please post a comment or link