scheme :: MULTOP_1:sch 1
FuncEx3D{ F₁() -> non empty set , F₂() -> non empty set , F₃() -> non empty set , F₄() -> non empty set , P₁[ object , object , object , object ] } :

ex f being Function of [:F₁(),F₂(),F₃():],F₄() st
for x being Element of F₁()
for y being Element of F₂()
for z being Element of F₃() holds P₁[x,y,z,f . [x,y,z]]

provided

A1: for x being Element of F₁()
for y being Element of F₂()
for z being Element of F₃() ex t being Element of F₄() st P₁[x,y,z,t]