A Semantic Data Base Model and Its Associated Structured User Interface.

摘要

The conventional approaches to the structuring of data bases provided in contemporary data base management systems are in many ways unsatisfactory for modelling data base application environments. The features they provide are too low-level, computer-oriented, are representational to allow the semantics of a data base to be directly expressed in its structure. The semantic data model (SDM) has been designed as a natural application modelling mechanism that can capture and express the structure of an application environment. The features of the SDM correspond to the principal intensional structures naturally occurring in contemporary data base applications. The SDM provides a rich but limited vocabulary of data structure types and primitive operations, striking a balance between semantic expressibility and the control of complexity. Furthermore, facilities for expressing derived (conceptually redundant) information are an essential part of the SDM; derived information is as prominent in the description of an SDM data base as is primitive data. The SDM is designed to enhance the effectiveness and usability of data base systems. There are many data base management systems in use today which represent a considerable investment on the parts of their developers and users; the SDM can be effectively used in conjunction with these existing data base systems to enhance their effectiveness and usability.