Reasoning and Merging in XML Data Integration

In this paper, we study the problem of making use of target constraints to integrate XML data from different sources under a target schema. We recognize that target constraints are necessary in data integration, as the constraints are essential part of data semantics, and should be satisfied by integrated data. When integrating data from multiple data sources with overlapping data, constraints can express data merging rules at the target as well. We give a general constraint model for XML to express target constraints, which extends the relational equality-generating and tuple- generating dependencies. We provide a chase method to reason about data in the integrated XML document based on target constraints, by inferring data values not given explicitly, and inserting new subtrees as necessary. Singleton and key constraints are used to uniquely specify a certain entity, as a rule for data merging in the integration.