Extended Disjunctive Normal Form for Efficient Processing of Re- Cursive Logic Queries
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Described in this article is the Extended Disjunctive Normal Form (EDNF) for efficiently processing a large class of logic queries. This class encompasses all the logic queries in function-free Horn-clause logic having recursions involving the Query goal. EDNF minimizes the need to create temporary tables that contain the intermediate results. It also eliminates the arbitrary processing structure imposed by the user-written rules. This makes it possible for the optimizer to search through alternative query processing strategies and choose the best one. Since the EDNF is in a form most amenable to database query optimization, this technique is especially useful in a loosely-coupled environment in which the existing database system takes care of data retrieval.