 reserve f,g for Function;
 reserve R for non empty reflexive RelStr;
 reserve R for non empty RelStr;
 reserve f for Function of the carrier of R, bool the carrier of R;

theorem :: j) version
  for x,y being Subset of R holds
    (f_0 R).(x \/ y) = (f_0 R).x \/ (f_0 R).y by Propj;
