Algebraic database migration to object technology

Abstract

Relational database systems represent the current standard technology for implementing database applications. Now that the object-oriented paradigm becomes more and more mature in all phases of the software engineering process, object-oriented DBMS are seriously considered for the seamless integration of object-oriented applications and data persistence. However, when reengineering existing applications or constructing new ones on top of relational databases, a large semantic gap between the new object model and the legacy database’s model must be bridged. We propose database migration to resolve this mismatch: the relational schema is transformed into an object-oriented one and the relational data is migrated to an object-oriented database. Existing approaches for migration do not exploit the full potential of the object-oriented paradigm so that the resulting object-oriented schema still “looks rather relational” and retains the drawbacks and weaknesses of the relational schema. We propose a redesign environment which allows to transform relational schemas into adequate object-oriented ones. Schemas and transformation rules are expressed in terms of a new data model, called semi object types (SOT). We also propose a formal foundation for SOT and transformation rules. This formalization makes it possible to automatically generate the data migration process.