An Effective Encoding Scheme for Spatial RDF Data∗

The RDF data model has recently been extended to support rep-resentation and querying of spatial information (i.e., locations and geometries), which is associated with RDF entities. Still, there are limited efforts towards extending RDF stores to efficiently support spatial queries, such as range selections (e.g., find entities within a given range) and spatial joins (e.g., find pairs of entities whose locations are close to each other). In this paper, we propose an ex-tension for RDF stores that supports efficient spatial data manage-ment. Our contributions include an effective encoding scheme for entities having spatial locations, the introduction of on-the-fly spa-tial filters and spatial join algorithms, and several optimizations that minimize the overhead of geometry and dictionary accesses. We implemented the proposed techniques as an extension to the open-source RDF-3X engine and we experimentally evaluated them us-ing real RDF knowledge bases. The results show that our system offers robust performance for spatial queries, while introducing lit-tle overhead to the original query engine. 1