Classification and compilation of linear recursive queries indeductive databases

The authors present a graph model which is powerful in classifying and compiling linear recursive formulas in deductive databases. The graph model consists of two kinds of graphs: I-graph and resolution graph. Essential properties of a recursive formula can be extracted from its I-graph, and the compiled formula and the query evaluation plan of the recursive formulas can be determined from its resolution graph. It is demonstrated that based on the graph model all the linear recursive formulas can be classified into a taxonomy of classes and each class shares common characteristics in query compilation and query processing. The compiled formulas and the corresponding query evaluation plans can be derived based on the study of the compilation of each class