14. The system of claim 9 , wherein the recommender adapted to determine the set of mappings of query communities from the first set of query communities to query communities from the second set of query communities comprises, for each unique pair of query communities comprising a query community from the first set of query communities and a query community from the second set of query communities, the recommender adapted to: determine, from the set of queries, a first amount of users who provided a query from the query community from the first set of query communities followed by a query from the query community from the second set of query communities; determine, from the set of queries, a second amount of users who provided a query from the query community from the second set of query communities followed by a query from the query community from the first set of query communities; and if the first amount is greater than a threshold amount, and the first amount is greater than the second amount, add a mapping from the query community from the first set of query communities to the query community from the second set of query communities to the set of mappings.
9. A system comprising: at least one computing device; and a recommender adapted to: receive a set of queries, wherein each query is associated with a user who provided the query and each query has an associated time; divide the received set of queries into a set of queries that are commercial queries and a set of queries that are non-commercial queries; generate a first set of query communities from the set of queries that are non-commercial queries and a second set of query communities from the set of queries that are commercial queries, wherein each query community comprises a plurality of queries of the set of queries and each query in a query community is related to each other query in the query community, wherein a first query is related to a second query if the first query and the second query were provided by the same user with associated times that are within a time window more than a threshold number of times; determine a set of mappings of query communities from the first set of query communities to query communities from the second set of query communities according to the users and times associated with the queries in the query communities; receive a query from the first set of query communities; and recommend one or more queries from the second set of query communities using the received query and the set of mappings.