Bidirectional conversion between XML documents and relational data bases

Abstract

Relational databases have been used as support to the information storage since a long time ago. Maintenance and the natural growing of information systems imply the reuse of existing databases but, many times, information is not stored on the most convenient structure or in the desired platform; then it becomes necessary to export it into another system or to transform its structure. These tasks should be executed in a fast and safe way, and as much automatized as possible. In the last years, XML was accepted as the neutral format for information representation. This is due, mainly, to two factors. On one hand, XML documents are purely textual files, structured and independent of any hardware or software platforms. On the other hand, more and more public domain tools are available, to help users transforming XML documents. The paper focus on the use XML as an interchange format between database management systems and presents an XML language, DBML, that allows the definition of the structure and the content of a relational database. It also introduces a methodology to convert a database into a DBML document and two tools that allow transforming DBML documents, into SQL and back. DBML and the two conversion functions (dbsql2dbml and dbml2dbsql) provided the basis to support the idea of designing a language to specify database transformations and developing a generator to automatically produce the transference processors; we finish the paper with the proposal of such a system.