> 4NF was explained confusingly because it's quite complex theory. The fact the author says 'to be best of his understanding' it is 4nf is kind of telling.
> My 'colleagues' (I am external) claim to know all this stuff, but in reality there is no proof they do; I have never seen them do things correctly with respect to dbs or software in general.
Wait I don't get it. Are you saying that "(instructor_id, skill_id); PK (instructor_id, skill_id)" (and the same for languages) is NOT in 4NF; and I am not right? What is in 4NF, then?