13. One or more non-transitory computer-readable media storing instructions that, when executed by one or more computing devices, cause: maintaining relationship data describing relationships between data objects in a collection of data objects; identifying search results for a set of query terms, each result of the search results being a subset of related data objects within the collection, the subset comprising, for each particular term of the query terms, at least one data object that matches the particular term; wherein identifying the search results comprises: identifying groups of initial data objects to investigate for the search results, the groups including at least a first group matching a first query term, a second group matching a second query term, and a third group matching a third query term; based on how often certain initial data objects appear both in the first group and the second group, removing, from the groups, initial data objects that are not found within both the first group and the second group; identifying particular subsets of related data objects within the collection by, based on the relationships, expanding networks of related data objects from the remaining initial data objects; determining which of the particular subsets qualify as the search results.
13. One or more non-transitory computer-readable media storing instructions that, when executed by one or more computing devices, cause: maintaining relationship data describing relationships between data objects in a collection of data objects; identifying search results for a set of query terms, each result of the search results being a subset of related data objects within the collection, the subset comprising, for each particular term of the query terms, at least one data object that matches the particular term; wherein identifying the search results comprises: identifying groups of initial data objects to investigate for the search results, the groups including at least a first group matching a first query term, a second group matching a second query term, and a third group matching a third query term; based on how often certain initial data objects appear both in the first group and the second group, removing, from the groups, initial data objects that are not found within both the first group and the second group; identifying particular subsets of related data objects within the collection by, based on the relationships, expanding networks of related data objects from the remaining initial data objects; determining which of the particular subsets qualify as the search results. 17. The one or more non-transitory computer-readable media of claim 13 , wherein the instructions, when executed by the one or more computing devices, further cause expanding networks of related data objects in an order that is based on one or more scores assigned to each of at least the remaining initial data objects, the one or more scores for a particular data objects comprising one or more of: a relationship score calculated from a link analysis of the collection; a metadata score for a particular metadata item to which the particular data object conforms, the metadata score calculated from a link analysis of different metadata items to which the data items in the collection conforms.