This article offers basic principles for use in determining how "relational" a DBMS product is — a challenge which faces many buyers today, because almost every vendor is claiming that his DBMS product is "relational". The material is likely to be of interest to vendors also. Some of them may not realize how far from the mark they are.

During the last three or four years several investigators have been exploring 'semantic models' for formatted data bases. The intent is to capture (in a more or less formal way) more of the meaning of the data, so that data base design can become more systematic and the data base system itself can behave more intelligently. Two major thrusts are clear:1) the search for meaningful units that are as small as possible --- atomic semantics2) the search for meaningful units that are larger than the usual n-ary relation --- molecular semantics.In this paper we propose extensions to the relational model to support certain atomic and molecular semantics. These extensions represent a synthesis of many ideas from the published work in semantic modeling.

During the last three or four years several investigators have been exploring “semantic models” for formatted databases. The intent is to capture (in a more or less formal way) more of the meaning of the data so that database design can become more systematic and the database system itself can behave more intelligently. Two major thrusts are clear. In this paper we propose extensions to the relational model to support certain atomic and molecular semantics. These extensions represent a synthesis of many ideas from the published work in semantic modeling plus the introduction of new rules for insertion, update, and deletion, as well as new algebraic operators.