A distribution graph including {HEAD ~ the nodes} involved in {TAIL ~ the distribution} spanned out by logical links assigned cost values is constructed 
A distribution graph including { HEAD ~ the nodes } involved in { TAIL ~ the distribution } spanned out by logical links assigned cost values is constructed
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH