A method and system for using social bookmarks wherein a social bookmark is a triplet of the entities of user, document, and tag. The method including: collecting multiple bookmarks; representing the bookmarks as a three-dimensional space or matrix of the number of times a user u, used tag t to bookmark document d; measuring the similarity of two entities of the same type; and using the similarity to weight bookmarks or entities. The weightings may be used to provide a measure of a usefulness of a bookmark for describing a document for retrieval purposes. Two-dimensions of the bookmark space may also be used to predict the third-dimension.