Theorem Provers as Question Answerers

T h i s paper d e s c r i b e s a d e d u c t i v e q u e s t i o n a n s w e r i n g comp u t e r program t h a t uses the Robinson r e s o l u t i o n p rocedu re t o p e r f o r m l o g i c a l i n f e r e n c e s and r e t r i e v e f a c t s o n the b a s i s o f a f a i r l y l a r g e body o f s t o r e d d a t a . I r r e l e v a n t searches and i n f e r e n c e s a r e k e p t to a minimum by means of some r e c e n t l y deve loped t h e o r e m p r o v i n g t e c h n i q u e s , most n o t a b l y M e l t z e r ' s P l d e d u c t i o n w i t h s e t o f s u p p o r t 1 and the ' f i r s t l i t e r a l r e s o l u t i o n ' method o f Hayes and K o w a l s k i , t o g e t h e r w i t h a d i c t i o n a r y l i s t i n g o f t he p remises i n t h e da ta base i n te rms o f t he p r e d i c a t e s and o t h e r key c o n s t a n t s o f t h e i r f i r s t l i t e r a l s . Us ing the s p e c i a l p r e d i c a t e Var o f Green and R a p h a e l , t h e program can hand le q u e s t i o n s r e q u i r i n g a l i s t o f answers , such as ' w h i c h (o r how many) i n d i v i d u a l s s a t i s f y a c o n d i t i o n 0 ? f , as well as simpler questions requiring a single answer, such as ' is individual a_ a 0?' In a series of tests using a data base containing the names and party a f f i l i ations of the senators, congressmen and governors of the f i f t y American states, the program has shown the abi l i ty to perform fair ly complex deductions eff iciently in the presence of a large number of irrelevant premises.