What is fourth normal form?

Question

SQL

On Habré I read one thing, on another site - another.
I will give an example:
There are tables: employees, employees_positions and employees_and_positions.
The first keeps employees.
The second stores positions.
And the third one brings it all together. Many-to-many.
An employee can have multiple positions. A position can have multiple employees. To whom the logic is now broken - this is normal. This is a rough example. But this moment is not important now. I'm talking about something else.
So. Is it 4nf?

Answer 1

fourth normal form

Answer 2

There is a tuple A, B, C where there is a dependency between A and B and between A and C, but there is no dependency between B and C. In this case, 4NF talks about the need to decompose the base