In this paper we present the data manipulation facility for a structured English query language (SEQUEL) which can be used for accessing data in an integrated relational data base. Without resorting to the concepts of bound variables and quantifiers SEQUEL identifies a set of simple operations on tabular structures, which can be shown to be of equivalent power to the first order predicate calculus. A SEQUEL user is presented with a consistent set of keyword English templates which reflect how people use tables to obtain information. Moreover, the SEQUEL user is able to compose these basic templates in a structured manner in order to form more complex queries. SEQUEL is intended as a data base sublanguage for both the professional programmer and the more infrequent data base user.
As computer systems become more advanced we see a gradual evolution from procedural to declarative problem specification. There are two major reasons for this evolution. First, a means must be found to lower software costs among professional programmers. The costs of program creation, maintenance, and modification have been rising very rapidly. The concepts of structured programming have been introduced in order to sinplify programming and reduce the cost of software. Secondly, there is an increasing need to bring the non-professional user into effective communication with a formatted data base. Much of the success of the computer industry dedepends on developing a class of users other than trained computer specialists.
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These rules are intended to simplify programming for the professional and to make data base interaction available to a new class of users. [ … ] A brief discussion of this new class of users is in order here. There are some users whose interaction with a computer is so infrequent or unstructured that the user is unwilling to learn a query language. For these users, natural language or menu selection seem to be the most viable alternatives. However, there is also a large class of users who, while they are not computer specialists, would be willing to learn to interact with a computer in a reasonably high-level, non-procedural query language. Examples of such users are accountants, engineers, architects, and urban planners. It is for this class of users that SEQUEL is intended. For this reason, SEQUEL emphasizes simple data structures and operations.
This simple block-structured English keyword syntax and simple operations on tables enable users to interact with the SEQUEL system with less training and sophistication than would be required in either a calculus-oriented system or a traditional procedural programming language.
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The resulting queries tend to be concise, clearly expressed, and easy to write, maintain, and modify.
EMP, SALES, SUPPLY, LOC and CLASS. It seems that Oracle's sample tables were inspired by this paper.