Automatic Migration and Wrapping of Database Applications - A Schema Transformation Approach

Integration of heterogeneous databases requires that semantic differences between schemas are resolved by a process of schema transformation. Previously, we have developed a general framework to support the schema transformation process, consisting of a hypergraph-based common data model and a set of primitive schema transformations defined for this model. Higher-level common data models and primitive schema transformations for them can be defined in terms of this lower-level model. In this paper, we show that a key feature of our framework is that both primitive and composite schema transformations are automatically reversible. We show how these transformations can be used to automatically migrate or wrap data, queries and updates between semantically equivalent schemas.We also show how to handle transformations between non-equivalent but overlapping schemas.We describe a prototype schema integration tool that supports this functionality. Finally, we briefly discuss how our approach can be extended to more sophisticated application logic such as constraints, deductive rules, and active rules.