Key Preserving P2P Data Transformation in XML

Transformation of data with any data model is an important activity to the database community. Specially in peer to peer(P2P) system, data transformation between two peers is a necessary task when data management is an issue. With the advent of XML as an widely used and adopted data representation and exchange format over the web, transformation of data in XML P2P systems is getting much interest. In XML P2P data transformation, a source schema with its conforming document needs to be transformed to a target schema with its conforming document. In addition, a source schema can have integrity constraints for better semantics. Then the constraints needs to be transformed and may not be preserved after the transformation. In this research, we study how XML keys are transformed, and whether the transformed keys are valid and preserved to the target schema in XML P2P data transformation. Towards this problem, we firstly define XML keys over Document Type Definition (DTD) and their satisfactions. We then show how the XML keys are transformed using transformation operations. Finally, we study the key preservation property of important XML transformation operators. We show that the important XML transformation operations are key preserving with necessary and sufficient conditions.