Importance computation can be made very query specific, by first
retrieving the top k results (e.g. using a vector space ranking
method), and then retrieving links that the results forward points to
(authorities) and also the links that are backwardly linking to it
(hubs). In its entirety, this graph of links is called the "base
set". Additional value can be extracted by also considering the other
links (new authorities) that the hubs point to, and the other links
(new hubs) that point to the authorities.