reserve i, j, k for Element of NAT,
  I for Element of Segm 8,
  i1, i2 for Element of NAT,
  d1, d2, d3, d4 for Element of SCM-Data-Loc,
  S for non empty 1-sorted;
reserve G for non empty 1-sorted;

theorem
  for s being SCM-State of G, t being Element of SCM-Data-Loc, u being
  Element of G holds SCM-Chg(s,t,u).NAT = s.NAT
proof
  let s be SCM-State of G, t be Element of SCM-Data-Loc, u be Element of G;
   NAT in SCM-Memory by AMI_2:22;
   then SCM-OK.NAT = 0 & SCM-OK.t = 1 by AMI_2:def 4;
   then not NAT in dom(t .--> u) by TARSKI:def 1;
  hence thesis by FUNCT_4:11;
end;
