{HEAD ~ A bounding web site} is characterized by {TAIL ~ the best data values} from among all field web sites 
is characterized by
{ HEAD ~ A bounding web site } is characterized by { TAIL ~ the best data values } from among all field web sites
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH