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 identifying from the unstructured data one or more relationships between entities of the structured information; extracting attribute values from the unstructured data for one or more entities of the 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; 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; and linking entities of the structured information to each other within the structured information based on the one or more relationships between those entities identified within the unstructured data.