Thus the basic meaning (which should be completed by some existential presuppositions) of (7) is given in (8):(8) (NO TWO LANGUAGES) (SOME AND NOT EVERY STUDENT) nom KNOW What (7) basically means is that there are no (two) languages which are known by some but not by all students and not that for every student there are two languages such that he/she knows them.
in this representation the use of the nominative case extension is essential.