QLever (pronounced , as in "clever") is an

open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...

triplestore A triplestore or RDF store is a purpose-built database for the storage and retrieval of triples through semantic queries. A triple is a data entity composed of subject– predicate– object, like "Bob is 35" (i.e., Bob's age measured in years i ...

and

graph database A graph database (GDB) is a database that uses graph structures for semantic queries with nodes, edges, and properties to represent and store data. A key concept of the system is the graph (or edge or relationship). The graph relates the dat ...

developed by a team at the

University of Freiburg The University of Freiburg (colloquially ), officially the Albert Ludwig University of Freiburg (), is a public university, public research university located in Freiburg im Breisgau, Baden-Württemberg, Germany. The university was founded in 1 ...

led by

Hannah Bast Hannah Bast is a German computer scientist known for her work on routing in transportation networks and search engines. She works as a professor at the University of Freiburg, where she holds the chair in algorithms and data structures and is d ...

. QLever performs high-performance queries of

semantic Web The Semantic Web, sometimes known as Web 3.0, is an extension of the World Wide Web through standards set by the World Wide Web Consortium (W3C). The goal of the Semantic Web is to make Internet data machine-readable. To enable the encoding o ...

knowledge base In computer science, a knowledge base (KB) is a set of sentences, each sentence given in a knowledge representation language, with interfaces to tell new sentences and to ask questions about what is known, where either of these interfaces migh ...

s, including

full-text search In Document retrieval, text retrieval, full-text search refers to techniques for searching a single computer-stored document or a collection in a full-text database. Full-text search is distinguished from searches based on metadata or on parts of ...

within text corpuses. A specialized user interface for QLever predictively

autocomplete Autocomplete, or word completion, is a feature in which an application software, application predicts the rest of a word a user is typing. In Android (operating system), Android and iOS smartphones, this is called predictive text. In graphical us ...

SPARQL SPARQL (pronounced ":wikt:sparkle, sparkle", a recursive acronym for SPARQL Protocol and RDF Query Language) is an RDF query language—that is, a Semantic Query, semantic query language for databases—able to retrieve and manipulate data sto ...

queries.

Characteristics

A 2023 study compared QLever with

Virtuoso A virtuoso (from Italian ''virtuoso'', or ; Late Latin ''virtuosus''; Latin ''virtus''; 'virtue', 'excellence' or 'skill') is an individual who possesses outstanding talent and technical ability in a particular art or field such as fine arts, ...

, Blazegraph, GraphDB, Stardog,

Apache Jena Apache Jena is an open source Semantic Web framework for Java. It provides an API to extract data from and write to RDF graphs. The graphs are represented as an abstract "model". A model can be sourced with data from files, databases, URLs or a ...

, 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.

The official QLever instance provides API endpoints for querying the following datasets: *

Wikidata Wikidata is a collaboratively edited multilingual knowledge graph hosted by the Wikimedia Foundation. It is a common source of open data that Wikimedia projects such as Wikipedia, and anyone else, are able to use under the CC0 public domain ...

Wikimedia Commons Wikimedia Commons, or simply Commons, is a wiki-based Digital library, media repository of Open content, free-to-use images, sounds, videos and other media. It is a project of the Wikimedia Foundation. Files from Wikimedia Commons can be used ...

* Freebase *

OpenStreetMap OpenStreetMap (abbreviated OSM) is a free, Open Database License, open geographic database, map database updated and maintained by a community of volunteers via open collaboration. Contributors collect data from surveying, surveys, trace from Ae ...

OpenHistoricalMap OpenHistoricalMap (also spelled Open Historical Map and abbreviated OHM) is an online collaborative mapping project developing a Historical atlas, historical map of the world using OpenStreetMap technology and processes. Whereas OpenStreetMap on ...

UniProt UniProt is a freely accessible database of protein sequence and functional information, many entries being derived from genome sequencing projects. It contains a large amount of information about the biological function of proteins derived fro ...

PubChem PubChem is a database of Chemistry, chemical molecules and their activities against biological assays. The system is maintained by the National Center for Biotechnology Information (NCBI), a component of the National Library of Medicine, which ...

DBLP DBLP is a computer science bibliography website. Starting in 1993 at Universität Trier in Germany, it grew from a small collection of HTML files and became an organization hosting a database and logic programming bibliography site. Since Novem ...

OpenCitations OpenCitations (established in 2010) is a project aiming to publish open bibliographic citation information in RDF. It produces the "OpenCitations Corpus" citation database in the process. Datasets OpenCitations publishes the following datas ...

IMDb IMDb, historically known as the Internet Movie Database, is an online database of information related to films, television series, podcasts, home videos, video games, and streaming content online – including cast, production crew and biograp ...

Integrated Authority File The (translated as ''Integrated Authority File'') or GND is an international authority file for the organisation of personal names, subject headings and corporate bodies from catalogues. It is used mainly for documentation in libraries and ...

YAGO Yago or YAGO may refer to: *Yagō, a term applied in traditional Japanese culture to names passed down within a guild, studio, or other circumstance other than blood relations *YAGO (database), a semantic knowledge base * Yago (name), includes lis ...

DBpedia DBpedia (from "DB" for "database") is a project aiming to extract structured content from the information created in the Wikipedia project. This structured information is made available on the World Wide Web using OpenLink Virtuoso. DBpedia a ...

* Wallscope Olympics database For OpenStreetMap and OpenHistoricalMap data, the QLever engine supports a limited subset of

GeoSPARQL GeoSPARQL is a model for representing and querying geospatial linked data for the Semantic Web. It is standardized by the Open Geospatial Consortium as OGC GeoSPARQL. The definition of a small ontology based on well-understood OGC standards is inte ...

functions, supplemented by a precomputed subset of GeoSPARQL relationships stored as dedicated triples.

Adoption

Besides the official instance, the QLever engine also powers the official SPARQL endpoint of

. QLever is one of the candidates to replace Blazegraph as the triplestore for the Wikidata Query Service.

References

External links

* * * {{GitHub, ad-freiburg/qlever-ui Triplestores Graph databases University of Freiburg

Characteristics

Contents

Adoption

See also

References

Further reading

External links