concepts of a data independent accessing model
The Data Independent Accessing Model (DIAM) represents a constructive combination of the formal mathematical and the evolutionary pragmatic approaches to a Generalized Data Base Management System. It aims at a complete separation between the user's (application programmer's) model of real-world objects, events, and the relationships among them, and the internal representation of those objects, events, and relationships. At the same time, it aims at complete flexibility of internal representation in terms of simple specifications, the effects of which are easy to understand. The DIAM encompasses four levels of descriptive models (Figure 1), each providing for flexible augmentation of the descriptions of the preceding level. Specifications at each level are retained in a catalog.
concept data model combinational formalism pragmatics general data base management systems completeness user applications programmer object event relationships intern representation timing flexibility effect