Zermelo–Fraenkel set theory
In the mathematical discipline of set theory, ramified forcing is the original form of forcing introduced by to prove the independence of the continuum hypothesis from Zermelo–Fraenkel set theory. Ramified forcing starts with a model of set theory in which the axiom of constructibility, , holds, and then builds up a larger model of Zermelo–Fraenkel set theory by adding a generic subset of a partially ordered set to , imitating Kurt Gödel's constructible hierarchy.