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

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