for x, y being object
for M being Pnet holds
( ( [x,y] in Flow M & x in the carrier' of M implies ( not x in the carrier of M & not y in the carrier' of M & y in the carrier of M ) ) & ( [x,y] in Flow M & y in the carrier' of M implies ( not y in the carrier of M & not x in the carrier' of M & x in the carrier of M ) ) & ( [x,y] in Flow M & x in the carrier of M implies ( not y in the carrier of M & not x in the carrier' of M & y in the carrier' of M ) ) & ( [x,y] in Flow M & y in the carrier of M implies ( not x in the carrier of M & not y in the carrier' of M & x in the carrier' of M ) ) )