1. A method, comprising: for a set of encoded Resource Description Format entities, attributes, values and encoded categories, forming a category index of encoded categories, each encoded category in the category index comprising a list of corresponding encoded entities; determining for each encoded attribute, those encoded entities that have encoded values for the encoded attribute; responsive to the determination, forming an attribute index of encoded attributes and their corresponding encoded entities and encoded values; storing the category index and the attribute index to form a knowledge database; decomposing a structured query into a plurality of simple queries; processing each of the plurality of simple queries in parallel by accessing the category index or the attribute index in the knowledge database to determine a list of encoded entities for each of the plurality of simple queries; determining an intersection for the lists of encoded entities to determine the encoded entities responsive to the structured query; and translating the encoded entities responsive to the structure query into original entities.