reserve x,y for object,X,Y for set;
reserve M for Pnet;

theorem
  for x holds the carrier of (Tsingle_f_net(x)) = {} &
  the carrier' of (Tsingle_f_net(x)) = {x} &
   Flow Tsingle_f_net x = {}
proof
  let x;
  {} misses {x} by XBOOLE_1:65;
  then Tsingle_f_net(x) = PT_net_Str (# {}, {x}, {}({},{x}), {}({x},{}) #)
     by Def1;
  hence thesis;
end;
