Reengineering relational databases to object-oriented: constructing the class hierarchy and migrating the data

The object-oriented data model is predicted to be the heart of the next generation of database systems. Users want to move from old legacy databases into applying this new technology that provides extensibility and flexibility in maintenance. However, a major limitation on the wide acceptance of object-oriented databases is the amount of time and money invested on existing database applications, which are based on conventional legacy systems. Users do not want to loose the huge amounts of data present in conventional databases. This paper presents a novel approach to transform a given conventional database into an object-oriented database. It is assumed that the necessary characteristics of the conventional database to be re-engineered are known and available. The source of these characteristics might be the data dictionary and/or an expert in the given conventional database. We implemented a system that builds an understanding of a given conventional database by taking these characteristics as input and produces the corresponding object-oriented database as output. The system derives a graph that summarizes the conceptual model. Links in the graph are classified into inheritance links and aggregation links. This classification leads to the class hierarchy. Finally, we handle the migration of data from the conventional database to the constructed object-oriented database.