The existing web of linked data inherently has distributed data sources. A federated SPARQL query system, which queries RDF data via multiple SPARQL endpoints, is expected to process queries on the basis of these distributed data sources. During a federated query, each data source may consist of a search space of nontrivial size. Therefore, finding the optimal join order to minimize the size of...

We provide an evaluation of query execution plans (QEP) in the case of queries with one or two spatial joins. The QEPs assume R -tree indexed relations and use a common set of spatial joins algorithms, among which one is a novel extension of a strategy based on an on-the-fly index creation prior to the join with another indexed relation. A common platform is used on which a set of spatial acces...

Similarity Joins are recognized among the most useful data processing and analysis operations. They retrieve all data pairs whose distances are smaller than a predefined threshold ε. While several standalone implementations have been proposed, very little work has addressed the implementation of Similarity Join as a physical database operator. In this paper, we focus on the study, design and im...

Among structured Peer-to-Peer systems, Chord has a general popularity due to its salient features like simplicity, high scalability, small path length with respect to network size, and flexibility on node join and departure. However, Chord doesn’t take into account the topology of underlying physical network when a new node is being added to the system, thus resulting in high routing late...

Many modern applications rely on high-performance processing of spatial data. Examples include location-based services, games, virtual worlds, and scientific simulations such as molecular dynamics and behavioral simulations. These applications deal with large numbers of moving objects that continuously sense their environment, and their data access can often be abstracted as a repeated spatial ...

The similarity join is an important database primitive which has been successfully applied to speed up data mining algorithms. In the similarity join, two point sets of a multidimensional vector space are combined such that the result contains all point pairs where the distance does not exceed a parameter ε. Due to its high practical relevance, many similarity join algorithms have been devised....

This paper extends earlier research on hash-join algorithms to a multiprocessor architecture. Implementations of a number of centralized join algorithms are described and measured. Evaluation of these algorithms served to verify earlier analytical results. In addition, they demonstrate that bit vector filtering provides dramatic improvement in the performance of all algorithms including the sor...