Software:QLever

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QLever
Original author(s)Hannah Bast, Björn Buchhold, Johannes Kalmbach, et al.[1][2]
Initial release2017; 9 years ago (2017)
Repositorygithub.com/ad-freiburg/qlever
Written inC++
Standard(s)SPARQL
Available inEnglish
TypeGraph database
LicenseApache License
Websiteqlever.dev

QLever (pronounced /ˈklɛvər/ KLEH-ver, as in "clever") is an open-source triplestore and graph database developed by a team at the University of Freiburg led by Hannah Bast. QLever performs high-performance queries of semantic Web knowledge bases, including full-text search within text corpuses.[1] A specialized user interface for QLever predictively autocompletes SPARQL queries.[2]

History

A 2023 study compared QLever with Virtuoso, Blazegraph, GraphDB, Stardog, Apache Jena, and Oxigraph. The study investigated a QLever version from 2021, concluding that it achieved fast execution of successful queries but offered limited support for complex SPARQL constructs.[3][4]

Contents

The official QLever instance provides API endpoints for querying the following datasets:[5]

For OpenStreetMap and OpenHistoricalMap data, the QLever engine supports a limited subset of GeoSPARQL functions, supplemented by a precomputed subset of GeoSPARQL relationships stored as dedicated triples.[6]

Adoption

Besides the official instance, the QLever engine also powers the official SPARQL endpoint of DBLP.[7] QLever is one of the candidates to replace Blazegraph as the triplestore for the Wikidata Query Service.[3][8]

See also

References

  1. ↑ 1.0 1.1 Bast & Buchhold 2017.
  2. ↑ 2.0 2.1 Bast et al. 2021.
  3. ↑ 3.0 3.1 Lam, An Ngoc; Elvesæter, Brian; Martin-Recuerda, Francisco (2023). "Evaluation of a Representative Selection of SPARQL Query Engines Using Wikidata". 13870. Springer, Cham. pp. 679–696. doi:10.1007/978-3-031-33455-9_40. ISBN 978-3-031-33454-2. https://2023.eswc-conferences.org/wp-content/uploads/2023/05/paper_Lam_2023_Evaluation.pdf. "To ensure that our limited selection of triple stores is representative and diverse, the following triplestores were evaluated: … QLever (commit version 742213facfcc80af11dade9a971fa6b09770f9c)…. QLever was very fast on success queries, but it offered limited support for queries with complex SPARQL constructs." 
  4. ↑ Kalmbach, Johannes (4 November 2021). "Final PR to integrate the SPARQL expressions into QLever". ad-freiburg/qlever. GitHub. https://github.com/ad-freiburg/qlever/commit/742213facfcc80af11dade9a971fa6b09770f9ca. Retrieved 22 March 2025. 
  5. ↑ "QLever". Freiburg im Breisgau: University of Freiburg Chair for Algorithms and Data Structures. https://qlever.cs.uni-freiburg.de/. Retrieved 13 July 2024. 
  6. ↑ Bast et al. 2021.
  7. ↑ "dblp SPARQL query service". Schloss Dagstuhl. https://blog.dblp.org/2024/09/09/introducing-our-public-sparql-query-service/. Retrieved 2024-11-09. 
  8. ↑ Woodie, Alex (10 July 2025). "Scaling the Knowledge Graph Behind Wikipedia". BigDATAwire (San Diego: Tabor Communications). https://www.bigdatawire.com/2025/07/10/scaling-the-knowledge-graph-behind-wikipedia/. Retrieved 1 August 2025. 

Further reading

  • Bast, Hannah; Brosi, Patrick; Kalmbach, Johannes; Lehmann, Axel (November 2–5, 2021). "An Efficient RDF Converter and SPARQL Endpoint for the Complete OpenStreetMap Data". SIGSPATIAL. Beijing: Association for Computing Machinery. doi:10.1145/3474717.3484256. ISBN 978-1-4503-8664-7. https://ad-publications.cs.uni-freiburg.de/SIGSPATIAL_osm2rdf_BBKL_2021.pdf. 
  • Bast, Hannah; Buchhold, Björn (November 6–10, 2017). "QLever: A Query Engine for Efficient SPARQL+Text Search". Singapore: Association for Computing Machinery. doi:10.1145/3132847.3132921. ISBN 978-1-4503-4918-5. https://ad-publications.cs.uni-freiburg.de/CIKM_qlever_BB_2017.pdf. 
  • Bast, Hannah; Kalmbach, Johannes; Klumpp, Theresa; Kramer, Florian; Schnelle, Niklas (29 April 2021). "Efficient SPARQL Autocompletion via SPARQL". arXiv:2104.14595v1 [cs.DB].



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