“5 Links of separation” is a principle to follow when creating your PBOK.
The principle states that you should be able to navigate from any note to any other note using 5 links.
Any many cases the first link or the first note to navigate to is your overall note, what I call my practice note.
From there you should be able to find any note by navigating through 4 notes.
This principle should be kept in mind when you are creating the note. Each note should have the path to the note understood when it is created. This is not something that should be left until you are searching for the note.
The wisdom in a PBOK is related to how efficiently you can navigate between notes.