A study of order transformations of hierarchical structures in IMS data bases

Abstract

Hierarchical structures are widely used in information processing. An application program written to traverse a hierarchical structure will not work properly, if at all, when the order of the structure (in the sense of tree order) is altered. This paper presents a method in the context of IMS systems to intercept and interpret data base manipulation commands issued by the application program to eliminate the necessity of reprogramming when a hierarchical structure is subject to an order transformation. Algorithms involving command substitution rules for various situations have been derived to insure the correct execution of application programs irrespective of the order of the structure.