A Deductive Question-Answer for Natural Language Inference The question-answering aspects of the Protosynthex III pro totype language processing system are described and exemplified in detail. The system is written in LISP 1.5 and operates on the Q-32 time-sharing system. The system's data structures and their semantic organization, the deductive question-answering formalism of relational properties and complex-relation-forming operators, and the question-answering procedures which employ these features in their operation are all described and illustrated. Examples of the system's performance and of the limitations of its question-answering capability are presented and discussed. It is shown that the use of semantic information in deductive question answering greatly facilitates the process, and that a top-down procedure which works from question to answer enables effective use to be made of this information. It is concluded that the development of Protosynthex III into a practically useful system to work with large data bases is possible but will require changes in both the data structures and the algorithms used for question answering. CACM March, 1970 Schwarcz, R. M. Burger, J. F. Simmons, R. F. question answering, natural language, Protosynthex III, LISP, semantics, artificial intelligence, computational linguistics, language processing, fact retrieval 3.42 3.61 CA700306 JB February 13, 1978 4:30 PM 2092 4 2092 2127 4 2092 1527 5 2092 2092 5 2092 2092 5 2092 2092 5 2092 2396 5 2092 1487 6 2092 1856 6 2092 2092 6 2092 2127 6 2092