1. A database system, comprising: a memory device having instructions stored thereon that, in response to execution by a processing device, cause the processing device to perform operations comprising: extracting information from unstructured personal textual data and structured data of a plurality of heterogeneous network sources of data of a personal data cloud of a user, wherein said extraction includes processing at least a portion of the unstructured personal textual data based on an analysis of at least a portion of the structured data; constructing, using automated semantic analysis that includes one or both of automatic clustering and tagging operations, a semantically indexed, integrated knowledge store for storage and future retrieval of the extracted information, the semantically indexed, integrated knowledge store including information derived algorithmically from the unstructured personal textual data and the structured data; identifying a natural language user request from the user; determining a semantic interpretation of the natural language user request, wherein determining the semantic interpretation includes referencing a stored ontology that defines a semantic relationship among a set of personal data terminology; querying the semantically-indexed, integrated knowledge store based at least in part on the semantic interpretation; and responding to the natural language user request by displaying one or more results of the querying, wherein the one or more results correspond to at least one item within the personal data cloud.