Simplification of the Computation of D+ We can simplify the computation of the closure of D by using the following rules(proved using rules 1-8). Multivalued union rule.If aB holds and ay holds,then o>>βy holds. Intersection rule.If a B holds and ay holds,then aBr holds. Difference rule.IfIf aB holds and ay holds,then aB-Y holds and ay-B holds. Database System Concepts,5th Ed. C.4 ©Silberschat乜，Korth and SudarshanDatabase System Concepts, 5 C.4 ©Silberschatz, Korth and Sudarshan th Ed. Simplification of the Computation of D+ We can simplify the computation of the closure of D by using the following rules (proved using rules 1-8). Multivalued union rule. If   holds and   holds, then   holds. Intersection rule. If   holds and   holds, then     holds. Difference rule. If If   holds and   holds, then   –  holds and   –  holds