reserve I, G, H for set, i, x for object,
  A, B, M for ManySortedSet of I,
  sf, sg, sh for Subset-Family of I,
  v, w for Subset of I,
  F for ManySortedFunction of I;

theorem :: SETFAM_1:3
  sf <> {} implies Intersect sf c= union sf
proof
  assume sf <> {};
  then Intersect sf = meet sf by SETFAM_1:def 9;
  hence thesis by SETFAM_1:2;
end;
