In calculating {HEAD ~ a route} through {TAIL ~ a network} of nodes and links, a standard constrained shortest path first method builds a network graph, accumulating a set of path data 
through
In calculating { HEAD ~ a route } through { TAIL ~ a network } of nodes and links , a standard constrained shortest path first method builds a network graph , accumulating a set of path data
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH