Deductive Methods for Large Data Bases

The design and prototype implementation of a deduct ive processor f o r e f f i c i e n t ex t rac t ion of i m p l i c i t in format ion from e x p l i c i t data stored w i t h i n a r e l a t i o n a l data-base system is descr ibed. General statements (premises or inference ru les ) as wel l as queries are expressed in a canonical form as imp l i ca t i ons . From user quer ies , the system constructs ske le ta l de r i va t ions (proof plans) through the use of a predicate connection graph, a pre-computed net s t ruc tu re represent ing possible deductive i n te rac t i ons among the general statements. The system incorporates techniques f o r rap id se lec t ion of small sets of re levant premises (by proof p lann ing) ; development and e labora t ion of proof p lans; proof plan v e r i f i c a ­ t i o n ; use of proof plans as a basis f o r deter ­ mining data-base access s t r a t e g i e s ; and i n s t a n t i a ­ t i o n o f plans ( i . e . , tu rn ing proof plans in to proofs) w i th re t r i eved data-base values. Examples of the cur rent c a p a b i l i t y of the system are i l l u s t r a t e d .