13. A computer-implemented method of retrieving/identifying a document comprising text stored in a document repository comprising: storing, at a memory, a graphical structure comprising a first plurality of nodes each representing a person, and a second plurality of nodes each representing a document in the document repository, the nodes being connected by edges according to automatically observed interactions between the represented people and documents, at least some of the nodes having one or more annotations each denoting a topic, an interaction of the interactions at least partially based on at least one of: a consumption activity by a person represented by a first node of the first plurality of nodes of a document represented by a first node of the second plurality of nodes, or a relationship between a first person represented by the first node of the first plurality of nodes, and a second person represented by a second node of the first plurality of nodes; computing, at a processor, distances between nodes of the graphical structure using the topic annotations; receiving, at an input/output controller, an identifier of a user who is represented by one of the first plurality of nodes; and automatically identifying one or more documents from the document repository by using the identifier and using the computed distances between nodes.
13. A computer-implemented method of retrieving/identifying a document comprising text stored in a document repository comprising: storing, at a memory, a graphical structure comprising a first plurality of nodes each representing a person, and a second plurality of nodes each representing a document in the document repository, the nodes being connected by edges according to automatically observed interactions between the represented people and documents, at least some of the nodes having one or more annotations each denoting a topic, an interaction of the interactions at least partially based on at least one of: a consumption activity by a person represented by a first node of the first plurality of nodes of a document represented by a first node of the second plurality of nodes, or a relationship between a first person represented by the first node of the first plurality of nodes, and a second person represented by a second node of the first plurality of nodes; computing, at a processor, distances between nodes of the graphical structure using the topic annotations; receiving, at an input/output controller, an identifier of a user who is represented by one of the first plurality of nodes; and automatically identifying one or more documents from the document repository by using the identifier and using the computed distances between nodes. 15. The method of claim 13 comprising automatically detecting at least one topic of a document of the document repository using an index of words, where words in the index have a plurality of associated topics weighted using frequency of observed co-occurrence of the word and associated topics in a corpus of documents which is the same or different from the document repository.