scheme :: SCHEME1:sch 21
FuncExCD2{ F₁() -> non empty set , F₂() -> non empty set , F₃() -> non empty set , P₁[ set , set ], F₄( set , set ) -> Element of F₃(), F₅( set , set ) -> Element of F₃() } :

ex f being Function of [:F₁(),F₂():],F₃() st
for c being Element of F₁()
for d being Element of F₂() st [c,d] in dom f holds
( ( P₁[c,d] implies f . [c,d] = F₄(c,d) ) & ( P₁[c,d] implies f . [c,d] = F₅(c,d) ) )