scheme :: FACIRC_1:sch 6
3AryBooleDef{ F₁( set , set , set ) -> Element of BOOLEAN } :

( ex f being Function of (3 -tuples_on BOOLEAN),BOOLEAN st
for x, y, z being Element of BOOLEAN holds f . <*x,y,z*> = F₁(x,y,z) & ( for f1, f2 being Function of (3 -tuples_on BOOLEAN),BOOLEAN st ( for x, y, z being Element of BOOLEAN holds f1 . <*x,y,z*> = F₁(x,y,z) ) & ( for x, y, z being Element of BOOLEAN holds f2 . <*x,y,z*> = F₁(x,y,z) ) holds
f1 = f2 ) )