Adding Conflict Resolution Features to a Query Language for Database Federations

A main problem of data integration is the treatment of conflicts caused by different modeling of real-world entities, different data models or simply by different representations of one and the same object. During the integration phase these conflicts have to be identified and resolved as part of the mapping between local and global schemata. Therefore, conflict resolution affects the definition of the integrated view as well as query transformation and evaluation. In this paper we present a SQL extension for defining and querying database federations. This language addresses in particular the resolution of integration conflicts by providing mechanisms for mapping attributes, restructuring relations as well as extended integration operations. Finally, the application of these resolution strategies is briefly explained by presenting a simple conflict resolution method.