1. A knowledge representation and retrieval system, comprising: one or more data stores having a knowledge base stored therein comprising structured data representing first knowledge; and one or more computing devices configured to: convert a natural language question to an internal query that represents an interpretation of the natural language question and has an internal format compatible with the structured data; compute one or more responses to the natural language question by processing the internal query with reference to the structured data, wherein the one or more responses include second knowledge derived from the first knowledge, the second knowledge not being stored in the knowledge base prior to receipt of the natural language question; and generate a definitive natural language answer corresponding to at least one of the one or more responses.