The present invention provides methods and apparatus, including computer
program products, implementing techniques for searching and ranking
linked information sources. The techniques include receiving multiple
content items from a corpus of content items; receiving digital
signatures each made by one of multiple agents, each digital signature
associating one of the agents with one or more of the content items; and
assigning a score to a first agent of the multiple agents, wherein the
score is based upon the content items associated with the first agent by
the digital signatures.