Towards the Preservation of Keys in XML Data Transformation for Integration

Transformation of a source schema with its conforming data to a target schema with its conforming data is an important activity in XML as two schemas in XML can represent same real world information. Specifically in XML data integration, transformation of a source to a target is regarded as an important task. An XML source schema can often be defined with XML key which is an important integrity constraint. Thus when a source schema with keys is transformed, keys need to be transformed as they are defined on the schema. Moreover there is a need to investigate whether the transformed keys are valid and preserved. In this paper, we study how XML keys are transformed, and whether the transformed keys are valid and preserved to the target schema. Towards this problem, we firstly define XML keys 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.