36. The system of claim 34 , where, when the one or more computer devices are to assign a rank score, the one or more computer devices are to: increase the rank score of the first document if the first document has hierarchical user-defined labels assigned to the first document by a plurality of different users.
34. A system comprising: one or more computer devices to: retrieve hierarchical user-defined labels assigned to a first document; represent a first relationship between the first document and a second document as a first link between the first document and the second document, where the first relationship includes at least one of: the first document and the second document sharing a same hierarchical user-defined label, the first document and the second document being associated with a same sub-directory, or the first document and the second document being associated with a same bookmark folder; represent a second relationship between the first document and a third document as a second link between the first document and the third document, where the second relationship includes at least one of: a hierarchical user-defined label, associated with the first document, and a hierarchical user-defined label, associated with the third document, being sibling labels, a sub-directory, associated with the first document, and a sub-directory, associated with the third document, being sibling sub-directories, or a bookmark folder, associated with the first document, and a bookmark folder, associated with the third document, being sibling bookmark folders; assign a rank score to the first document based on the first link and based on the second link, where the first link contributes more to the rank score than the second link; receive a search query; generate an information retrieval score for the first document based on the search query; generate a total rank score for the first document based on the assigned rank score and based on the generated information retrieval score; and present one or more documents selected from a collection of documents, where the one or more presented documents include the first document and where a position of the first document among the one or more presented documents is based on the generated total rank score.