The most important motivation for the research work that resulted in the relational model was the objective of providing a sharp and clear boundary b… - Edgar F. Codd

It is no surprise that attempts such as those of CODASYL and ANSI to develop data structure language (DDL) and data manipulation language (DML) in separate communities have yielded many misunderstandings and incompatibilities.

Relational processing entails treating whole relationships as operands. Its primary purpose is loop-avoidance, an absolute requirement for end users to be productive at all, and a clear productivity booster for application programmers.

The adverse impact on development productivity of requiring programmers to navigate along access paths to reach target data [...] was enormous. In addition, it was not possible to make slight changes in the layout in storage without simultaneously having to revise all programs that relied on the previous structure. [...] As a result, far too much manpower was being invested in continual (and avoidable) maintenance of application programs.