| Abstract: | Recursive rules are important to deductive databases. A recursive rule may be compiled into expansions. In this article, the variable-predicate graph (V-P graph) based on the α-graph by loannidis is developed to represent linear recursive function-free rules and their expansions. A naming convention is used for variables and predicates in the V-P graph so that all equivalent recursive rules may map into a unique V-P graph. We propose a graphic construction method (g.c.m.) which derives V-P graphs of expansions directly from the V-P graph of the original rule. This graphic representation reveals some expansion properties not easy to obtain otherwise. We also propose a rule rewriting method in the context of deductive database so that constants, repeated distinguished variables, and/or repeated recursive variables may be removed from recursive rules. |
