QLever

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.{{cite conference|title=Evaluation of a Representative Selection of SPARQL Query Engines Using Wikidata|first1=An Ngoc|last1=Lam|first2=Brian|last2=Elvesæter|first3=Francisco|last3=Martin-Recuerda|work=Extended Semantic Web Conference|series=Lecture Notes in Computer Science|publisher=Springer, Cham|volume=13870|date=2023|url=https://2023.eswc-conferences.org/wp-content/uploads/2023/05/paper_Lam_2023_Evaluation.pdf|doi=10.1007/978-3-031-33455-9_40|quote=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.}}{{cite web|title=Final PR to integrate the SPARQL expressions into QLever|first=Johannes|last=Kalmbach|work=ad-freiburg/qlever|publisher=GitHub|date=4 November 2021|accessdate=22 March 2025|id=742213f|url=https://github.com/ad-freiburg/qlever/commit/742213facfcc80af11dade9a971fa6b09770f9ca}}

The official QLever instance provides API endpoints for querying the following datasets:{{cite web|title=QLever|publisher=University of Freiburg Chair for Algorithms and Data Structures|location=Freiburg im Breisgau|accessdate=13 July 2024|url=https://qlever.cs.uni-freiburg.de/}}

• 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.{{sfn|Bast|Brosi|Kalmbach|Lehmann|2021}}

Besides the official instance, the QLever engine also powers the official SPARQL endpoint of DBLP.{{cite web|title=dblp SPARQL query service|publisher=Schloss Dagstuhl |accessdate=2024-11-09 |url=https://blog.dblp.org/2024/09/09/introducing-our-public-sparql-query-service/}} QLever is one of the candidates to replace Blazegraph as the triplestore for the Wikidata Query Service.

{{Commons category|QLever}}

• List of SPARQL implementations

{{reflist}}

• {{cite conference|title=An Efficient RDF Converter and SPARQL Endpoint for the Complete OpenStreetMap Data|first1=Hannah|last1=Bast|author1-link=Hannah Bast|first2=Patrick|last2=Brosi|first3=Johannes|last3=Kalmbach|first4=Axel|last4=Lehmann|conference=SIGSPATIAL|date=November 2–5, 2021|publisher=Association for Computing Machinery|location=Beijing|isbn=978-1-4503-8664-7|doi=10.1145/3474717.3484256|url=https://ad-publications.cs.uni-freiburg.de/SIGSPATIAL_osm2rdf_BBKL_2021.pdf}}
• {{cite conference|title=QLever: A Query Engine for Efficient SPARQL+Text Search|first1=Hannah|last1=Bast|first2=Björn|last2=Buchhold|work=Conference on Information and Knowledge Management|date=November 6–10, 2017|location=Singapore|publisher=Association for Computing Machinery|isbn=978-1-4503-4918-5|doi=10.1145/3132847.3132921|url=https://ad-publications.cs.uni-freiburg.de/CIKM_qlever_BB_2017.pdf}}
• {{cite arXiv|title=Efficient SPARQL Autocompletion via SPARQL|first1=Hannah|last1=Bast|first2=Johannes|last2=Kalmbach|first3=Theresa|last3=Klumpp|first4=Florian|last4=Kramer|first5=Niklas|last5=Schnelle|date=29 April 2021|eprint=2104.14595v1|class=cs.DB}}

• {{Official website|https://qlever.cs.uni-freiburg.de/}}
• {{GitHub|ad-freiburg/qlever}}
• {{GitHub|ad-freiburg/qlever-ui}}

Category:Triplestores

Category:Graph databases

Category:University of Freiburg