Schema Evolution for New Database Applications: A Frame Model Approach

摘要

In this paper, we present a frame model approach to integrate existing databases and evolve them to support new database applications. The approach employed the joint top-down and bottom-up methodology. The bottom-up schema integration technique is taken to integrate existing database schemata to produce the global schema (B-Schema). Schemata from various systems are transformed to one common data model to capture as many data semantics from each input schema as possible. A Frame Model, an object-relational extension to the EER model is proposed as the common data model. The constraint enforcement mechanism of this model provides a tighter bound in capturing the data semantics and the integrity constraint from the original schemata. It possesses a dynamic data structure that adds the automation features to the process of schema integration. Details of the integration procedures and the advantages of using the frame model in schema integration are presented. The top-down approach uses the joint data- and functional-analysis. The B-Schema is evolved by comparing it with the generated T-Schema. This facilitates an evolutionary approach to integrate existing databases to support new applications. A case study is presented to illustrate the methodology.