reserve R for non empty RelStr,
  N for net of R,
  i for Element of N;

theorem Th25:
  for S being non empty 1-sorted, e being Element of S,
  x being Element of Net-Str e holds x = e
proof
  let S be non empty 1-sorted, e be Element of S, x be Element of Net-Str e;
  the carrier of Net-Str e = {e} by Def11;
  hence thesis by TARSKI:def 1;
end;
