For the weighting of query's keyphrase graph, a strategy
was chosen so that the sum of all the keyphrase's weight
equal to 1. First, we apply the two principles above to
every pairs of keyphrase in the query to decide which one
is more important. Then a graph can be plotted based on
this “more important” relation. If keyphrase a is more
important than keyphrase b, we assume there is a “link”
from b to a, that is to say “b link to a” or “a is linked to by
b”. The famous PageRank algorithm will then be used to
weight keyphrase.