DB4GL - An Intelligent Database System

Abstract

Current research within the Department of Computer Studies at Sheffield City Polytechnic indicates that it is possible to define a generalised database architecture which results in a worthwhile simplification of the traditional applications programming task. The approach adopted stems from the derivation, from normalisation procedures, of all the association relationships which exist between a set of entities, and then selecting the relevant subset of entities and association relationships for a specific application program. This subset is used to generate a data access schema, which has the important property that multiple data realisations can be performed on linked entities in anticipation of eventual demand. This reduces considerably the need for the programmer to specify explicit file handling operations within an application program. The data access schema is in fact one of four major structural software components in an application program which may be specified and generated. The other components are:-

• 1. an information description schema, one per entity, which specifies record actions, data item transfers and global integrity rules,

• 2. a process schema, which contains details of local integrity rules, that is, local to a specific application, and processing requests,

• 3. a presentation object, which contains details of user presentation in terms of screens, reports and graphical output, as well as error handling and the overall sequencing of the applications task.

In DB4GL it is possible to specify the architectural features of these four software components through the use of special software tools, for example, a normalisation engine, or, a screen painter and also to define integrity rules and simple processing requirements. These specifications are used in the application generation process.