 reserve R for 1-sorted;
 reserve X,Y for Subset of R;
 reserve R for finite 1-sorted;
 reserve X,Y for Subset of R;
 reserve R for finite Approximation_Space;
 reserve X,Y,Z,W for Subset of R;

theorem Kappa2RIF4:
  kappa_2 (X,Y) = 0 implies X misses Y
  proof
    assume kappa_2 (X,Y) = 0; then
    X = [#]R & Y = {} by Prop4b;
    hence thesis;
  end;
