Comment on “Segment Synthesis in Logical Data Base Design” [Letter to the Editor]

The examples shown in Figs. 2 and 3 of [1] illustrate the existence of simple cycles in the data model between the department and the manager of each case. Such relations, which are cyclic on a one-to-one basis, are frequent, both in the conceptual construction of data models by users and in the implementation of a data base for multi-file systems. To indicate this simple equivalency, the relation (D, M) can be replaced by an equivalent single domain, say X . Because of the frequency of occurrence of binary one-to-one relations, I have termed such relations a lexicon [2]. On applying this simplification, the result of the analysis for minimum cover given in [1] is a single set of relations as follows: R1(E, X, JC) R2 (X, CT) X(D, M).