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As object-oriented model becomes the trend of database technology, there is a need to convert relational to object-oriented database system to improve productivity and flexibility. The changeover includes schema translation, data conversion and program conversion. This paper describes a methodology for integrating schema translation and data conversion. Schema translation involves semantic reconstruction and the mapping of relational schema into object-oriented schema. Data conversion involves unloading tuples of relations into sequential files and reloading them into object-oriented classes files. The methodology preserves the constraints of the relational database by mapping the equivalent data dependencies.

With XML adopted as the technology trend on the Internet, and with investment in the current relational database systems, companies must convert their relational data into XML documents for data transmission on the Internet. In the process, to preserve the users' relational data requirements of data constraints into the converted XML documents, we must define a meaningful root element for each XML document. The construction of an XML document is based on the root element and its relevant elements. The root element can be selected from a relational entity table in the existing relational database, which depends on the requirements to present the business behind. The relevant elements are mapped from the related entities, based on the navigability of the chosen entity. The derived root and relevant elements can form a Data Type Definition Graph (DTD-graph) of an XML conceptual schema diagram which can be mapped into a Data Type Definition (DTD) of an XML schema. The result is a translated XML schema with semantic constraints transferred from a relational conceptual schema of an Extended Entity Relationship (EER) model. The data conversion from relational data to the XML documents can be done after the schema translation. The relational data are loaded into XML documents according to the translated DTD.

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