a searching unit to search the route information of the respective links connected via {HEAD ~ the respective node} corresponding to {TAIL ~ the starting position}; and 
corresponding to
a searching unit to search the route information of the respective links connected via { HEAD ~ the respective node } corresponding to { TAIL ~ the starting position } ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH