1. A system, comprising: a storage device; and a processor configured to operate a machine-implemented data extractor and correlator configured to: extract personal data from a first heterogeneous group of network sources, wherein at least one of the network sources of the first heterogeneous group corresponds to a different user account than another one of the network sources of the first heterogeneous group, the personal data including names, locations, and/or contact information associated persons and places; construct a semantically-indexed knowledge store in the storage device for future retrieval of the personal data associated with the persons and places; extract additional information from documents in a second group of network sources that is different than the first heterogeneous group of network sources, wherein the second group of network sources includes at least one network source and each one of said at least one network source is different than each network source of the first heterogeneous group of network sources, the additional information extracted from one(s) of the network sources of the second group that are associated with the persons and places; correlate the additional information with the semantically-indexed knowledge store to identify additional names, locations, and/or contact information associated with the persons and places; store the additional information as part of the personal data associated with the persons and places; receive a natural language user request from a user; determine a semantic interpretation of the natural language user request; query the semantically-indexed integrated knowledge store based on the semantic interpretation of the natural language user request; and display results including at least some of the names, locations, and/or contact information associated with the persons or places responsive to the natural language user request.