1. A computer-implemented method of supplementing structured information within a data system for entities based on unstructured data comprising: analyzing a document with unstructured data and extracting attribute values from the unstructured data for one or more entities of the data system associated with structured information; retrieving entity records with structured information from the data system based on the extracted attribute values; constructing entity references for corresponding one or more entities of the data system based on a comparison of the retrieved entity records and the extracted attribute values; and linking the entity references to the corresponding one or more entities within the data system, wherein the entity references include extracted attributes from the unstructured data for corresponding linked entities.