End user logical database design: The structured entity model approach.

摘要

We live in the Information Age. The effective use of information to manage organizational resources is the key to an organization's competitive power. Thus, a database plays a major role in the Information Age. A well designed database contains relevant, nonredundant, and consistent data. However, a well designed database is rarely achieved in practice. One major reason for this problem is the lack of effective support for logical database design. Since the late 1980s, various methodologies for database design have been introduced, based on the relational model, the functional model, the semantic database model, and the entity structure model. They all have, however, a common drawback: the successful design of database systems requires the experience, skills, and competence of a database analyst/designer. Unfortunately, such database analyst/designers are a scarce resource in organizations. The Structured Entity Model (SEM) method, as an alternative diagrammatic method developed by this research, facilitates the logical design phases of database system development. Because of the hierarchical structure and decomposition constructs of SEM, it can help a novice designer in performing top-down structured analysis and design of databases. SEM also achieves high semantic expressiveness by using a frame representation for entities and three general association categories (aspect, specialization, and multiple decomposition) for relationships. This also enables SEM to have high potential as a knowledge representation scheme for an integrated heterogeneous database system. Unlike most methods, the SEM method does not require designers to have knowledge of normalization theory in order to design a logical database. Thus, an end-user will be able to complete logical database design successfully using this approach. In this research, existing data models used for a logical database design were first studied. Second, the framework of SEM and the design approach using SEM were described and then compared with other data models and their use. Third, the effectiveness of the SEM method was validated in two experiments using novice designers and by a case analysis. In the final chapter of this dissertation, future research directions, such as the design of a logical database design expert system based on the SEM method and applications of this approach to other problems, such as the problems in integration of multiple databases and in an intelligent mail system, are discussed.