An English Language Question Answering System for a Large Relational Database By typing requests in English, casual users will be able to obtain explicit answers from a large relational database of aircraft flight and maintenance data using a system called PLANES. The design and implementation of this system is described and illustrated with detailed examples of the operation of system components and examples of overall system operation. The language processing portion of the system uses a number of augmented transition networks, each of which matches phrases with a specific meaning, along with context registers (his tory keepers) and concept case frames; these are used for judging meaningfulness of questions, generating dialogue for clarifying partially understood questions, and resolving ellipsis and pronoun reference problems. Other system components construct a formal query for the relational database, and optimize the order of searching relations. Methods are discussed for handling vague or complex questions and for providing browsing ability. Also included are discussions of important issues in programming natural language systems for limited domains, and the relationship of this system to others. CACM July, 1978 Waltz, D. Question answering, relational database, natural language, database front end, artificial intelligence, dialogue, query generation, information retrieval, natural language programming 3.42 3.60 3.69 3.74 3.79 CA780701 DH February 8, 1979 4:26 PM 2155 4 3087 2406 4 3087 2581 4 3087 2710 4 3087 2715 4 3087 2716 4 3087 2717 4 3087 2718 4 3087 2739 4 3087 2765 4 3087 2795 4 3087 2817 4 3087 2888 4 3087 2901 4 3087 2921 4 3087 2957 4 3087 2959 4 3087 2965 4 3087 3087 4 3087 3087 4 3087 3154 4 3087 1989 5 3087 2046 5 3087 3087 5 3087 3087 5 3087 3087 5 3087