6. The article of manufacture of claim 1 , wherein the strength value of the directed relationship from the first document to the first session of queries in the first pair of entities is based on how many documents are viewed during the first session and whether the first document is viewed during the first session, and wherein the strength value of the directed relationship from the second session of queries to the second document in the second pair of entities is based on how many sessions the second document was viewed in and whether the second document is viewed during the second session.
1. An article of manufacture, comprising: a computer readable medium; and instructions stored in the computer readable medium which, when executed by one or more computers, cause the one or more computers to perform operations comprising: obtaining data representing entities, each entity being a query, a document, a session of queries, a time, or a domain of a document; identifying a plurality of pairs of entities from a subset of the entities from search history data, where each pair is either: (1) (i) a query paired with (ii) another query, a document, a session of queries, or a time, or (2) (i) a document paired with (ii) a session of queries, or (3) two documents paired with each other, and where the plurality of pairs of entities comprise a first pair of entities that is a first document paired with a first session of queries and a second pair of entities that is a second session of queries paired with a second document; generating, for each pair of entities, using the search history data, a respective directed relationship having a respective strength value and connecting a first entity of the pair to a second entity of the pair; and determining, for any two entities that are directly or indirectly connected through directed relationships, a relevance score from strength values of the directed relationships connecting the two entities.