QLever

QLever (pronounced, 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. A specialized user interface for QLever predictively autocompletes SPARQL queries.

QLever is one of the candidates to replace Blazegraph as the triplestore for the Wikidata Query Service. A 2023 study found that, compared to other triplestores, QLever achieved fast execution of successful queries but offered limited support for complex SPARQL constructs.

Contents
The official QLever server provides access to the following datasets:


 * Wikidata
 * Wikimedia Commons
 * Freebase
 * OpenStreetMap
 * OpenHistoricalMap
 * UniProt
 * PubChem
 * DBLP
 * OpenCitations
 * IMDb
 * Integrated Authority File
 * YAGO
 * DBpedia
 * Wallscope Olympics database

Although the QLever engine lacks support for GeoSPARQL functions per se, the official server precomputes a subset of GeoSPARQL relationships into dedicated triples for OpenStreetMap and OpenHistoricalMap data.