What grammar form is "Es muss gemacht worden sein"?

Question

I thought the following sentence was *Perfekt Passive mit Modalverb (PPmMV)*: > Es muss gemacht worden sein. But I just found a book which says that "PPmMV" is: > Es hat gemacht werden müssen. So what grammar form is "Es muss gemacht worden sein" (if this is correct at all)?

Answer 1

They both are, but they make different statements.

Es hat gemacht werden müssen. ==> It needed to be done.(statement of necessity)

Es muss gemacht worden sein ==> It had to have been done. (statement of probability)

HTH

Armin