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The Odyssey Approach for Optimizing Federated SPARQL Queries [chapter]

Gabriela Montoya, Hala Skaf-Molli, Katja Hose
2017 Lecture Notes in Computer Science  
Answering queries over a federation of SPARQL endpoints requires combining data from more than one data source.  ...  To overcome these challenges, most federated query engines rely on heuristics to reduce the space of possible query execution plans or on dynamic programming strategies to produce optimal plans.  ...  Introduction Federated SPARQL query engines [1, 4, 7, 14, 17] answer SPARQL queries over a federation of SPARQL endpoints.  ... 
doi:10.1007/978-3-319-68288-4_28 fatcat:u7mr2ig2g5dvpmnpjmwen3cx6u

Semantic Web Technologies And Big Data Infrastructures: Sparql Federated Querying Of Heterogeneous Big Data Stores

Stasinos Konstantopoulos, Angelos Charalambidis, Giannis Mouchakis, Antonis Troumpoukis, Jürgen Jakobitsch, Vangelis Karkaletsis
2016 Zenodo  
The paper presents an extension of the Semagrow federated SPARQL query processor that is able to seamlessly federated SPARQL endpoints, Cassandra databases, and Solr databases, and discusses future directions  ...  federations of such heterogeneous systems.  ...  Semagrow is such a federated query processing system 3 that provides a single SPARQL endpoint that federates multiple remote SPARQL endpoints, transparently optimizing queries and dynamically integrating  ... 
doi:10.5281/zenodo.160170 fatcat:ie53rcd23bgbda4umsmzyiundm

Discovering, Indexing and Interlinking Information Resources

Fabrizio Celli, Johannes Keizer, Yves Jaques, Stasinos Konstantopoulos, Dušan Vudragović
2015 F1000Research  
We also discuss the SemaGrow Stack, a query federation and data integration infrastructure used to estimate the semantic distance between crawled web resources and AGRIS.  ...  The SemaGrow Stack implements a SPARQL endpoint that federates SPARQL endpoints, transparently optimizing federated queries and dynamically integrating heterogeneous There are several key features of  ...  Using the SemaGrow Stack and the single query "federated" mode, the SPARQL query to implement the algorithm is: This SPARQL query sorts resources from the Crawler Database by the number of AGROVOC URIs  ... 
doi:10.12688/f1000research.6848.1 pmid:26834982 pmcid:PMC4722689 fatcat:wlsbfr2r2fffdgkgbgp3juo7ba

Discovering, Indexing and Interlinking Information Resources

Fabrizio Celli, Johannes Keizer, Yves Jaques, Stasinos Konstantopoulos, Dušan Vudragović
2015 F1000Research  
We also discuss the SemaGrow Stack, a query federation and data integration infrastructure used to estimate the semantic distance between crawled web resources and AGRIS.  ...  Performance experiments were performed again using a bigger test set and we compared execution time in the "individual" mode with the execution time in the "federated" mode.  ...  The SemaGrow Stack implements a SPARQL endpoint that federates SPARQL endpoints, transparently optimizing federated queries and dynamically integrating heterogeneous data models by applying the appropriate  ... 
doi:10.12688/f1000research.6848.2 pmid:26834982 pmcid:PMC4722689 fatcat:3pethxje5bahrpqislz5rgwavy

Dataset Descriptions for Optimizing Federated Querying

Angelos Charalambidis, Stasinos Konstantopoulos, Vangelis Karkaletsis
2015 Proceedings of the 24th International Conference on World Wide Web - WWW '15 Companion  
In this poster we describe an extension of VoID that provides the expressivity needed in order to support the query planning methods typically used in federated querying.  ...  VoID is a notable exception, providing some expressivity for describing subsets and their contents and can, to some extent, be used for discovering relevant resources and for optimizing querying.  ...  CONCLUSIONS Sevod is used in the Semagrow Stack, 1 an infrastructure for deploying a SPARQL federation endpoint that automatically breaks up queries into fragments, each comprising one or more query patterns  ... 
doi:10.1145/2740908.2742779 dblp:conf/www/CharalambidisKK15 fatcat:wwwnonwamrf7pfmijzcl5lguvy

Developing A Benchmark Suite For Semantic Web Data From Existing Workflows

Antonis Troumpoukis, Angelos Charalambidis, Giannis Mouchakis, Stasinos Konstantopoulos, Ronald Siebes, Victor de Boer, Stian Soiland-Reyes, Daniela Digles
2016 Zenodo  
This paper presents work in progress towards developing a new benchmark for federated query processing systems.  ...  The value of this queryset is that it is realistic but at the same time it comprises complex queries that test all features of modern query processing systems.  ...  that support the Sesame API, such as SemaGrow [2] , FedX [13] and SPLENDID [4] federators.  ... 
doi:10.5281/zenodo.159568 fatcat:4hxjyzyiirhcdlckrpyhujk6y4

The Sevod Vocabulary For Dataset Descriptions For Federated Querying

Stasinos Konstantopoulos, Angelos Charalambidis, Antonis Troumpoukis, Giannis Mouchakis, Vangelis Karkaletsis
2017 Zenodo  
In this paper we describe the Sevod vocabulary, an extension of VoID that provides the expressivity needed in order to support the query planning methods typically used in federated querying.  ...  VoID is a notable exception, providing some expressivity for describing subsets and their contents and can, to some extent, be used for discovering relevant resources and for optimizing querying.  ...  The extension is designed to address federated SPARQL requirements extracted by analysing the information needs of current federated SPARQL query processors.  ... 
doi:10.5281/zenodo.997602 fatcat:eil4yse4dfehhoneip3ennjiza

Virtual Knowledge Graphs: An Overview of Systems and Use Cases

Guohui Xiao, Linfang Ding, Benjamin Cogrel, Diego Calvanese
2019 Data Intelligence  
On the other end, few SPARQL federators, such as SemaGrow  22 [49] do not have this restriction, and automatically generate a query plan for retrieving all the relevant content from the SPARQL endpoints  ...  Federation can be done at two different levels: at the data source level (SQL federation) or at the SPARQL endpoint level (SPARQL federation). SQL federation.  ... 
doi:10.1162/dint_a_00011 fatcat:dogtoffhbncx7lxxagytwlxz2u

Heuristics-based Query Reordering for Federated Queries in SPARQL 1.1 and SPARQL-LD [article]

Thanos Yannakis, Pavlos Fafalios, Yannis Tzitzikas
2018 arXiv   pre-print
The federated query extension of SPARQL 1.1 allows executing queries distributed over different SPARQL endpoints.  ...  Such a query optimization approach is widely applicable since it can be exploited on top of existing SPARQL 1.1 and SPARQL-LD implementations.  ...  Regarding more recent works, SemaGrow [6] is a federated SPARQL querying system that uses metadata about the federated data sources to optimize query execution.  ... 
arXiv:1810.09780v1 fatcat:4g4yabj5k5fhxmmunbymikqrou

FedQPL: A Language for Logical Query Plans over Heterogeneous Federations of RDF Data Sources (Extended Version) [article]

Sijin Cheng, Olaf Hartig
2020 arXiv   pre-print
A challenge for planning the execution of queries over such a federation is that the federation may be heterogeneous in terms of the types of data access interfaces provided by the federation members.  ...  Moreover, we show that the source selection problem is NP-hard and in Σ_2^P, and we provide a comprehensive set of rewriting rules that can be used as a basis for query optimization.  ...  Concrete examples of such algorithms can be found in the SPARQL endpoint federation engines FedX [25] , SemaGrow [7] , and CostFed [22] , as well as in the brTPF client [14] .  ... 
arXiv:2010.01190v1 fatcat:36qkdhlgjvauzdsy52jvfgjapu

Chapter 5 Federated Query Processing [chapter]

Kemele M. Endris, Maria-Esther Vidal, Damien Graux
2020 Lecture Notes in Computer Science  
Federated query processing techniques provide a solution to scale up to large volumes of data distributed across multiple data sources.  ...  Federated query processing techniques resort to source descriptions to identify relevant data sources for a query, as well as to find efficient execution plans that minimize the total execution time of  ...  As a result, diverse federated SPARQL query engines have been defined that enable users to execute queries over a federation of SPARQL endpoints.  ... 
doi:10.1007/978-3-030-53199-7_5 fatcat:o5wzimjwbzantbnbmvmjujoine

Towards the Integration of Agricultural Data from Heterogeneous Sources: Perspectives for the French Agricultural Context Using Semantic Technologies [chapter]

Shufan Jiang, Rafael Angarita, Raja Chiky, Stéphane Cormier, Francis Rousseaux
2020 Lecture Notes in Business Information Processing  
[9] , which is an open-source infrastructure for linked open data (LOD) integration that federates SPARQL endpoints from different providers.  ...  queries to validate the ontology design.  ... 
doi:10.1007/978-3-030-49165-9_8 fatcat:ejtamsf54rcmxoygrbwd5b6x7q

Analysis of Big Data technologies for use in agro-environmental science

Rob Lokers, Rob Knapen, Sander Janssen, Yke van Randen, Jacques Jansen
2016 Environmental Modelling & Software  
(LIAISE), 318497 (SemaGrow) and 284181 (Trees4Future) and the Ministry of Economic Affairs of the Netherlands.  ...  The SemaGrow Stack (https://github.com/semagrow/semagrow) is a 'federated SPARQL query processor' that can efficiently query a set of distributed heterogeneous data nodes.  ...  It includes a query planner that uses metadata about the nodes of the federation to optimize the query execution.  ... 
doi:10.1016/j.envsoft.2016.07.017 fatcat:e3yabrkudbctbjzug77nej643u

Where is My URI? [chapter]

Andre Valdestilhas, Tommaso Soru, Markus Nentwig, Edgard Marx, Muhammad Saleem, Axel-Cyrille Ngonga Ngomo
2018 Lecture Notes in Computer Science  
In the next step, the federated query processing engine makes use of the source selection information to generate an optimized query execution plan.  ...  In particular, our service can be helpful during the source selection and query planning in cost-based SPARQL federation engines such SPLENDID [6] , SemaGrow [3] , HiBISCuS [13] , CostFed [10] , etc  ... 
doi:10.1007/978-3-319-93417-4_43 fatcat:gdvzp2zvtnesrbsq6pjjdk2axe

ExtremeEarth Meets Satellite Data From Space

Desta Haileselassie Hagos, Theofilos Kakantousis, Vladimir Vlassov, Sina Sheikholeslami, Tianze Wang, Jim Dowling, Claudia Paris, Daniele Marinelli, Giulio Weikmann, Lorenzo Bruzzone, Salman Khaleghian, Thomas Krmer (+14 others)
2021 IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing  
endpoint using SPARQL SERVICE 12 for federation.  ...  We are currently working on efficient federated query processing techniques and integrate them in SemaGrow.  ... 
doi:10.1109/jstars.2021.3107982 fatcat:fxmpayska5bvlj7ibw3peqhuzu
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