UBC Theses and Dissertations
View integration in database design Wagner, Christian
The purpose of this research is the formalization of a method of bottom up database design known as view integration. View integration is one of the main steps of an acknowledged database design procedure, the New Orleans Database Design Workshop procedure. This procedure develops a global database (global schema) for an organization from small partial databases (user views). Individual user views are representations of the data relevant to the users' organizational tasks. Views will overlap since users will share data to some extent. View integration has to merge views without duplicating the information presented in multiple views. The task of merging views without duplication is complicated by the fact that users have different perceptions of the world which lead them to represent the same data differently, the most simple form of different perceptions being naming conflicts such as the occurrence of synonyms. Within the last 13 years a variety of approaches to solve the integration task has been reported. Many of the approaches have neglected the problem of conflicting views altogether, leaving its solution to the database designer. Integration methods that performed conflict resolution did it in an unsystematic and incomplete fashion. Often these methods dealt with conflict situations only if information for their resolution was conveniently available. This research fills that gap. A conflict analysis procedure is outlined which considers all possible conflict conditions and transforms them into conditions that can be merged by means of previously developed techniques. The research proceeds in two steps. First, a conflict analysis procedure is developed that ignores the information requirements problem by assuming complete information. This simplification allows the concentration on completeness of the procedure, since one does not have to be concerned with the difficulties involved in gathering the required information. The second step relaxes the assumption of complete information. Difficult information requirements are identified and replaced by more easily satisfied ones. Main contributions to knowledge are (1) a complete understanding of the factors causing conflicts between views, (2) detection of substitutes for difficult information requirements. Other contributions are (3) suggestions for the development of a semantic data dictionary, (4) an alternative method for the design of knowledge based systems, and (5) suggestions for efficient bottom up systems design strategies.
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