SPARQL
Query language for RDF (Resource Description Framework). W3C standard 2008. Drives the semantic web + knowledge graphs. SELECT ?x WHERE { ?x rdf:type :Person }.
Triple format: subject-predicate-object. Wikidata, DBpedia, UniProt have large SPARQL endpoints. Tim Berners-Lee's Semantic Web vision (early 2000s) didn't become what he hoped — outside life sciences + Wikipedia, RDF is marginal. Knowledge graphs live on in newer form (Neo4j-style graph DBs, OpenAI ChatGPT knowledge graph in the background). The Wikidata Query Service is the most practical SPARQL use today.