Preserving key in XML data transformation

Transformation of XML data is an important task in data exchange, data publishing and data integration. Specifically in data integration, data in XML sources is transformed to match the target schema. Some of these sources have XML keys defined. When the data is transformed, the keys also need to be transformed for constraint comparisons, consistency checking and unification in the target schema. Thus, how the keys are transformed, and whether the transformed keys are valid and preserved to the target schema are important problems in XML data transformation and integration. Towards this problem, we firstly define XML keys and their satisfactions. We then study how keys are transformed and whether transformed keys are valid when a source schema is transformed to a target schema. Finally we show whether the transformed keys are satisfied by the transformed document.