Compiling rules and queries in knowledge base systems: a substitution-based approach

The use of negative information and the unrestricted use of quantifiers in the body of a rule enhances the expressive power of deductive database systems. The authors introduce a more relaxed version of conventional (Skolem) function-free databases, called acceptable databases which generalize the class of allowed databases by accepting occurrences of universal quantifiers for variables occurring in positive literals and existential quantifiers for variables occurring in negative literals in the body of an IDB rule. The compilation technique suitable for compiling acceptable IDB rules based on the substitution rule is addressed. They show the correctness of the substitution-based compilation by proving completeness and soundness of the substitution rule