for C1, C2 being Coherence_Space
for X being Subset of [:(union C1),(union C2):] st ( for a, b being set st {a,b} in C1 holds
for y1, y2 being object st [a,y1] in X & [b,y2] in X holds
{y1,y2} in C2 ) & ( for a, b being set st {a,b} in C1 holds
for y being object st [a,y] in X & [b,y] in X holds
a = b ) holds
ex f being U-linear Function of C1,C2 st X = LinTrace f