reserve i,j,e,u for object;
reserve I for set; 
reserve x,X,Y,Z,V for ManySortedSet of I;

theorem Th111:
  X misses Y implies X (/\) Y = EmptyMS I
proof
  assume
A1: X misses Y;
  now
    let i be object;
    assume
A2: i in I;
    then
A3: X.i misses Y.i by A1;
    thus (X (/\) Y).i = X.i /\ Y.i by A2,Def5
      .= {} by A3;
  end;
  hence thesis by Th6;
end;
