Federated database systems for managing distributed, heterogeneous, and autonomous databases
ACM Computing Surveys (CSUR) - Special issue on heterogeneous databases
Query optimization in the presence of limited access patterns
SIGMOD '99 Proceedings of the 1999 ACM SIGMOD international conference on Management of data
The state of the art in distributed query processing
ACM Computing Surveys (CSUR)
Access path selection in a relational database management system
SIGMOD '79 Proceedings of the 1979 ACM SIGMOD international conference on Management of data
Optimizing Queries Across Diverse Data Sources
VLDB '97 Proceedings of the 23rd International Conference on Very Large Data Bases
SchemaSQL - A Language for Interoperability in Relational Multi-Database Systems
VLDB '96 Proceedings of the 22th International Conference on Very Large Data Bases
Index structures and algorithms for querying distributed RDF repositories
Proceedings of the 13th international conference on World Wide Web
Optimized Index Structures for Querying RDF from the Web
LA-WEB '05 Proceedings of the Third Latin American Web Congress
Semantics and complexity of SPARQL
ISWC'06 Proceedings of the 5th international conference on The Semantic Web
ISWC'06 Proceedings of the 5th international conference on The Semantic Web
A Framework for the Partial Evaluation of SPARQL Queries
SUM '08 Proceedings of the 2nd international conference on Scalable Uncertainty Management
Proceedings of the 10th International Conference on Information Integration and Web-based Applications & Services
Semantically-Aided Data-Aware Service Workflow Composition
SOFSEM '09 Proceedings of the 35th Conference on Current Trends in Theory and Practice of Computer Science
Rapid prototyping of semantic mash-ups through semantic web pipes
Proceedings of the 18th international conference on World wide web
Hermes: Data Web search on a pay-as-you-go integration infrastructure
Web Semantics: Science, Services and Agents on the World Wide Web
Web Semantics: Science, Services and Agents on the World Wide Web
Marvin: Distributed reasoning over large-scale Semantic Web data
Web Semantics: Science, Services and Agents on the World Wide Web
Towards a Mediator Based on OWL and SPARQL
WSKS '09 Proceedings of the 2nd World Summit on the Knowledge Society: Visioning and Engineering the Knowledge Society. A Web Science Perspective
Executing SPARQL Queries over the Web of Linked Data
ISWC '09 Proceedings of the 8th International Semantic Web Conference
SHARE: A Semantic Web Query Engine for Bioinformatics
ASWC '09 Proceedings of the 4th Asian Conference on The Semantic Web
SPARQL query rewriting for implementing data integration over linked data
Proceedings of the 2010 EDBT/ICDT Workshops
Data summaries for on-demand queries over linked data
Proceedings of the 19th international conference on World wide web
RDFProv: A relational RDF store for querying and managing scientific workflow provenance
Data & Knowledge Engineering
An evaluation of approaches to federated query processing over linked data
Proceedings of the 6th International Conference on Semantic Systems
Ontology-based semantic data processing in semantic programming language
CAR'10 Proceedings of the 2nd international Asia conference on Informatics in control, automation and robotics - Volume 1
Customisable query resolution in biology and medicine
HIKM '10 Proceedings of the Fourth Australasian Workshop on Health Informatics and Knowledge Management - Volume 108
Towards large-scale scientific dataspaces for e-science applications
DASFAA'10 Proceedings of the 15th international conference on Database systems for advanced applications
A flexible rule-based method for interlinking, integrating, and enriching user data
ICWE'10 Proceedings of the 10th international conference on Web engineering
Directing status messages to their audience in online communities
COIN'09 Proceedings of the 5th international conference on Coordination, organizations, institutions, and norms in agent systems
Model and prototype for querying multiple linked scientific datasets
Future Generation Computer Systems
SPARQL query optimization on top of DHTs
ISWC'10 Proceedings of the 9th international semantic web conference on The semantic web - Volume Part I
Query processing in a three-level ontology-based data integration system
Proceedings of the 12th International Conference on Information Integration and Web-based Applications & Services
Linked provenance data: A semantic Web-based approach to interoperable workflow traces
Future Generation Computer Systems
WS-Aggregation: distributed aggregation of web services data
Proceedings of the 2011 ACM Symposium on Applied Computing
Creating knowledge out of interlinked data: making the web a data washing machine
Proceedings of the International Conference on Web Intelligence, Mining and Semantics
Semantics and optimization of the SPARQL 1.1 federation extension
ESWC'11 Proceedings of the 8th extended semantic web conference on The semanic web: research and applications - Volume Part II
FedX: a federation layer for distributed query processing on linked open data
ESWC'11 Proceedings of the 8th extended semantic web conference on The semanic web: research and applications - Volume Part II
SDKB'10 Proceedings of the 4th international conference on Semantics in data and knowledge bases
Database foundations for scalable RDF processing
RW'11 Proceedings of the 7th international conference on Reasoning web: semantic technologies for the web of data
Transparent mobile querying of online RDF sources using semantic indexing and caching
WISE'11 Proceedings of the 12th international conference on Web information system engineering
ANAPSID: an adaptive query processing engine for SPARQL endpoints
ISWC'11 Proceedings of the 10th international conference on The semantic web - Volume Part I
FedX: optimization techniques for federated query processing on linked data
ISWC'11 Proceedings of the 10th international conference on The semantic web - Volume Part I
Lightweighting the web of data through compact RDF/HDT
CAEPIA'11 Proceedings of the 14th international conference on Advances in artificial intelligence: spanish association for artificial intelligence
ADERIS: an adaptive query processor for joining federated SPARQL endpoints
OTM'11 Proceedings of the 2011th Confederated international conference on On the move to meaningful internet systems - Volume Part II
Linked data indexing methods: a survey
OTM'11 Proceedings of the 2011th Confederated international conference on On the move to meaningful internet systems
Searching and browsing Linked Data with SWSE: The Semantic Web Search Engine
Web Semantics: Science, Services and Agents on the World Wide Web
ADERIS: adaptively integrating RDF data from SPARQL endpoints
DASFAA'10 Proceedings of the 15th international conference on Database Systems for Advanced Applications - Volume Part II
Scalable distributed indexing and query processing over Linked Data
Web Semantics: Science, Services and Agents on the World Wide Web
Adaptive integration of distributed semantic web data
DNIS'10 Proceedings of the 6th international conference on Databases in Networked Information Systems
Semantic navigation on the web of data: specification of routes, web fragments and actions
Proceedings of the 21st international conference on World Wide Web
Database techniques for linked data management
SIGMOD '12 Proceedings of the 2012 ACM SIGMOD International Conference on Management of Data
Towards benefit-based RDF source selection for SPARQL queries
SWIM '12 Proceedings of the 4th International Workshop on Semantic Web Information Management
Pay-as-you-go data integration for linked data: opportunities, challenges and architectures
SWIM '12 Proceedings of the 4th International Workshop on Semantic Web Information Management
Efficient distributed query processing for autonomous RDF databases
Proceedings of the 15th International Conference on Extending Database Technology
SPARQL-RW: transparent query access over mapped RDF data sources
Proceedings of the 15th International Conference on Extending Database Technology
Graph pattern matching revised for social network analysis
Proceedings of the 15th International Conference on Database Theory
Performance guarantees for distributed reachability queries
Proceedings of the VLDB Endowment
LodLive, exploring the web of data
Proceedings of the 8th International Conference on Semantic Systems
Evaluating graph traversal algorithms for distributed SPARQL query optimization
JIST'11 Proceedings of the 2011 joint international conference on The Semantic Web
Freshening up while staying fast: towards hybrid SPARQL queries
EKAW'12 Proceedings of the 18th international conference on Knowledge Engineering and Knowledge Management
Improving the recall of live linked data querying through reasoning
RR'12 Proceedings of the 6th international conference on Web Reasoning and Rule Systems
SPLODGE: systematic generation of SPARQL benchmark queries for linked open data
ISWC'12 Proceedings of the 11th international conference on The Semantic Web - Volume Part I
Hybrid SPARQL queries: fresh vs. fast results
ISWC'12 Proceedings of the 11th international conference on The Semantic Web - Volume Part I
Benchmarking federated SPARQL query engines: are existing testbeds enough?
ISWC'12 Proceedings of the 11th international conference on The Semantic Web - Volume Part II
ER'12 Proceedings of the 2012 international conference on Advances in Conceptual Modeling
Federating queries in SPARQL 1.1: Syntax, semantics and evaluation
Web Semantics: Science, Services and Agents on the World Wide Web
Mediating accesses to multiple information sources in a multi-lingual application
ICCCI'12 Proceedings of the 4th international conference on Computational Collective Intelligence: technologies and applications - Volume Part I
Structure inference for linked data sources using clustering
Proceedings of the Joint EDBT/ICDT 2013 Workshops
KGRAM Versatile Inference and Query Engine for the Web of Linked Data
WI-IAT '12 Proceedings of the The 2012 IEEE/WIC/ACM International Joint Conferences on Web Intelligence and Intelligent Agent Technology - Volume 01
Construction and applicability of military ontology for semantic data processing
Proceedings of the 3rd International Conference on Web Intelligence, Mining and Semantics
Colledge: a vision of collaborative knowledge networks
Proceedings of the 2nd International Workshop on Semantic Search over the Web
srCE: a collaborative editing of scalable semantic stores on P2P networks
International Journal of Computer Applications in Technology
SPARQL Endpoint Metrics for Quality-Aware Linked Data Consumption
Proceedings of International Conference on Information Integration and Web-based Applications & Services
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Integrated access to multiple distributed and autonomous RDF data sources is a key challenge for many semantic web applications. As a reaction to this challenge, SPARQL, the W3C Recommendation for an RDF query language, supports querying of multiple RDF graphs. However, the current standard does not provide transparent query federation, which makes query formulation hard and lengthy. Furthermore, current implementations of SPARQL load all RDF graphs mentioned in a query to the local machine. This usually incurs a large overhead in network traffic, and sometimes is simply impossible for technical or legal reasons. To overcome these problems we present DARQ, an engine for federated SPARQL queries. DARQ provides transparent query access to multiple SPARQL services, i.e., it gives the user the impression to query one single RDF graph despite the real data being distributed on the web. A service description language enables the query engine to decompose a query into sub-queries, each of which can be answered by an individual service. DARQ also uses query rewriting and cost-based query optimization to speed-up query execution. Experiments show that these optimizations significantly improve query performance even when only a very limited amount of statistical information is available. DARQ is available under GPL License at http://darq.sf.net/.