scheme :: DOMAIN_1:sch 9
SubsetFD2{ F₁() -> non empty set , F₂() -> non empty set , F₃() -> non empty set , F₄( object , object ) -> Element of F₃(), P₁[ object , object ] } :

{ F₄(x,y) where x is Element of F₁(), y is Element of F₂() : P₁[x,y] } is Subset of F₃()