Mapping XML DTDs to Relational Schema

Abstract

As Extensible Markup Language(XML)[W3COla, ABS99] is emerging as the data format of the web era. This is creating a new set of data management requirements involving XML, such as the need to store and query XML doc­ uments. One way to satisfy these requirements is using a relational database by transforming XML data into relations. However, given the wide variety of XML applications and the mismatch between XML's nested-tree structure and the flat tuples of the relational model, storing XML documents in rela­ tional databases presents interesting challenges. The problem of transforming XML data from XML files into the tabular data that can be managed by relational database management system is a very interesting problem. The existing transformation techniques that transform XML documents to rela­ tions are not complete in the sense that they focus only on structural aspects, while ignoring semantic aspects. In this thesis, we propose a new mapping technique that describes how the various definitions in a given XML DTD. such as elements, attributes, parent-child relationships, and ID-IDREF(s) at­ tributes can be mapped to entities and relationships, describes how to handle the Union types that are i10t present in relational model, and shows that XML's ordered data model can be efficiently supported by the unordered relational data model. Our approach is different from the existing approaches in that. we consider semantic constraints in the XML model, and they are captured in our resulting relational schema. Also we present a mapping-aware technique that