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Efficient query routing in distributed spatial databases

Spatial databases are prominently used in Geographic Information System (GIS) applications. However, many of the current architectures rely on a centralized data repository. The next evolution will be GIS applications that utilize and integrate a multitude of remotely accessible data sets, for example via Web services. Our involvement in a project where geotechnical borehole information is retrieved from a large number of repositories that are under different administrative control has motivated us to design an efficient distributed access structure and routing middleware for spatial queries. In this study we present our middleware design based on distributed R-tree and Quadtree index structures. Importantly, the framework supports both spatial range and <i>k</i> nearest neighbor queries. We have performed a theoretical analysis and simulations with synthetic and real data sets. The results show a large reduction in message traffic to a level only slightly above what is minimally necessary.