QLever
| Original author(s) | Hannah Bast, Björn Buchhold, Johannes Kalmbach, et al.[1][2] |
|---|---|
| Initial release | 2017 |
| Repository | github |
| Written in | C++ |
| Standard(s) | SPARQL |
| Available in | English |
| Type | Graph database |
| License | Apache License |
| Website | qlever |
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]
Characteristics
[edit]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
[edit]The official QLever instance provides API endpoints for querying the following datasets:[5]
- Wikidata
- Wikimedia Commons
- Freebase
- OpenStreetMap
- OpenHistoricalMap
- UniProt
- PubChem
- DBLP
- OpenCitations
- IMDb
- Integrated Authority File
- YAGO
- DBpedia
- Wallscope Olympics database
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
[edit]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]
See also
[edit]
References
[edit]- ^ a b Bast & Buchhold 2017.
- ^ a b Bast et al. 2021.
- ^ a b Lam, An Ngoc; Elvesæter, Brian; Martin-Recuerda, Francisco (2023). Evaluation of a Representative Selection of SPARQL Query Engines Using Wikidata (PDF). Extended Semantic Web Conference. Lecture Notes in Computer Science. Vol. 13870. Springer, Cham. doi:10.1007/978-3-031-33455-9_40.
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.
- ^ Kalmbach, Johannes (4 November 2021). "Final PR to integrate the SPARQL expressions into QLever". ad-freiburg/qlever. GitHub. 742213f. Retrieved 22 March 2025.
- ^ "QLever". Freiburg im Breisgau: University of Freiburg Chair for Algorithms and Data Structures. Retrieved 13 July 2024.
- ^ Bast et al. 2021.
- ^ "dblp SPARQL query service". Schloss Dagstuhl. Retrieved 2024-11-09.
Further reading
[edit]- Bast, Hannah; Brosi, Patrick; Kalmbach, Johannes; Lehmann, Axel (November 2–5, 2021). An Efficient RDF Converter and SPARQL Endpoint for the Complete OpenStreetMap Data (PDF). SIGSPATIAL. Beijing: Association for Computing Machinery. doi:10.1145/3474717.3484256. ISBN 978-1-4503-8664-7.
- Bast, Hannah; Buchhold, Björn (November 6–10, 2017). QLever: A Query Engine for Efficient SPARQL+Text Search (PDF). Conference on Information and Knowledge Management. Singapore: Association for Computing Machinery. doi:10.1145/3132847.3132921. ISBN 978-1-4503-4918-5.
- Bast, Hannah; Kalmbach, Johannes; Klumpp, Theresa; Kramer, Florian; Schnelle, Niklas (29 April 2021). "Efficient SPARQL Autocompletion via SPARQL". arXiv:2104.14595v1 [cs.DB].