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    • Big spatial and spatio-temporal data analytics systems 

      Velentzas P., Corral A., Vassilakopoulos M. (2021)
      We are living in the era of Big Data, and Spatial and Spatio-temporal Data are not an exception. Mobile apps, cars, GPS devices, ships, airplanes, medical devices, IoT devices, etc. are generating explosive amounts of data ...

    • Database design of a geo-environmental information system 

      Roumelis, G.; Loukopoulos, T.; Vassilakopoulos, M. (2014)
      Environmental protection from productive investments becomes a major task for enterprises and constitutes a critical competitiveness factor. The region of Central Greece presents many serious and particular environmental ...

    • Double chain-star: An RDF indexing scheme for fast processing of SPARQL joins 

      Meimaris M., Papastefanatos G. (2016)
      State of the art RDF stores often rely on exhaustive indexing and sequential (self-)joins for SPARQL query processing. However, query execution is dependent on, and often limited by the underlying storage and indexing ...

    • Extended characteristic sets: Graph indexing for SPARQL Query Optimization 

      Meimaris M., Papastefanatos G., Mamoulis N., Anagnostopoulos I. (2017)
      SPARQL query execution in state of the art RDF engines depends on, and is often limited by the underlying storage and indexing schemes. Typically, these systems exhaustively store permutations of the standard three-column ...

    • Improving Distance-Join Query processing with Voronoi-Diagram based partitioning in SpatialHadoop 

      García-García F., Corral A., Iribarne L., Vassilakopoulos M. (2020)
      SpatialHadoop is an extended MapReduce framework supporting global indexing techniques that partition spatial datasets across several machines and improve spatial query processing performance compared to traditional Hadoop ...

    • Join-queries between two spatial datasets indexed by a single R*-tree 

      Vassilakopoulos, M.; Corral, A.; Karanikolas, N. N. (2011)
      A spatial join, a common query in Spatial Databases and Geographical Information Systems (GIS), consists in testing every possible pair of data elements belonging to two spatial datasets against a spatial predicate. This ...

    • Nearest Neighbor Algorithms using xBR-Trees 

      Roumelis, G.; Vassilakopoulos, M.; Corral, A. (2011)
      One of the common queries in spatial databases is the (K) Nearest Neighbor Query that discovers the (K) closest objects to a query object. Processing of spatial queries, in most cases, is accomplished by indexing spatial ...

    • Predictive join processing between regions and moving objects 

      Corral, A.; Torres, M.; Vassilakopoulos, M.; Manolopoulos, Y. (2008)
      The family of R-trees is suitable for indexing various kinds of multidimensional objects. TPR*-trees are R-tree based structures that have been proposed for indexing a moving object database, e.g. a data-base of moving ...

    • Voronoi-diagram based partitioning for distance join query processing in spatialhadoop 

      García-García F., Corral A., Iribarne L., Vassilakopoulos M. (2018)
      SpatialHadoop is an extended MapReduce framework supporting global indexing techniques that partition spatial data across several machines and improve query processing performance compared to traditional Hadoop systems. ...