A System For Integrating Multiple Heterogeneous Databases

Information integration is very important for advanced database applications,Object Deputy Model can be used as common data model for information Integration.It can solve the problem of all kinds of heterogeneous database sources. The object deputy model is more flexible than the traditional object-oriented model. It can provide inheritance for specialization, generation and aggregation. In addition, the view mechanism is easy to be implemented by the object deputy model. The use of the object deputy model as the common data model can facilitate the creation of the federated schema.The major features of deputy objects are summarized as follows.1. A deputy object has its own persistent identifier, and may have additional attributes and methods that are not derived from its source objects.2. The attributes and methods of and object can be inherited by its deputy objects.The inheritance is realized through switching operations that can change the names and types of the inherited attributes and methods.3. There is a bilateral link between an object and one of its deputy objects, which allows not only inheritance but also update propagation between them.Because information integration is based on object deputy model, accessed data must be object-oriented data. If we can implement a interface between object-oriented data and non object-Oriented data, we can tranverse the data according to query data. Nowadays the most popular database is relational database, so we implement the oracle9i database system interface and the object-oriented interface of postgresql database that is a land of object-relaiton open-source database system, and then we can access the data from the database system, using the object-oriented methods.Through establishing the source objects and deputy objects, the corresponding relations about query handle can be implemented better. Accroding to object deputy model, application can translate the query disposal of the deputy object into the ones of the local database sources, it also return query results from local database sources, according to the application user's requirements. We have implemented object deputy model in Smalltalk. In this paper, we discuss how to realize integration of heterogeneous databases based on object deputy model in Smalltalk.