#semantic

The EMBL-EBI Ontology Lookup Service (OLS) as an API — a single access point to more than 280 biomedical and scientific ontologies and controlled vocabularies in one place: the Gene Ontology (GO), the Human Disease Ontology (DOID), the Human Phenotype Ontology (HP), ChEBI (chemical entities), Uberon (anatomy), the Experimental Factor Ontology (EFO), Mondo, NCIt and many more. /v1/search?q=diabetes searches terms across all ontologies (or restrict to one with ontology=doid), returning each match's label, OBO id (such as DOID:9351 or GO:0008150), ontology, IRI and a short definition. /v1/term?ontology=doid&id=DOID:9351 returns a single term's detail — its label, definition, IRI, synonyms and whether it is obsolete. /v1/ontologies browses the available ontologies with their id, title, description and number of terms. OBO ids look like DOID:9351, GO:0008150, HP:0000118 or CHEBI:15377. Ideal for biomedical natural-language processing, data annotation and harmonisation, autocomplete over scientific terminology, and semantic and knowledge-graph tooling. Data from EMBL-EBI OLS (open). This is a general ontology / controlled-vocabulary lookup spanning many domains — broader than a single medical thesaurus such as MeSH.

api.oanor.com/ols-api

The Wikidata structured knowledge graph as an API — the free, collaborative, multilingual knowledgebase that underpins Wikipedia and thousands of apps, powered by the official Wikidata action API. Search the knowledge graph by text to find entities and their Q-ids; read an entity for its label, description, aliases, a summary of its statements (each property with sample values), sitelink count and Wikipedia link; fetch the full claims for a property of an entity (values, ranks, qualifiers); resolve up to 50 Q/P ids to human-readable labels and descriptions in a single call; and look up any property's label, description and datatype. Covers tens of millions of items — people, places, organisations, works, species, events and concepts — in any language. Ideal for knowledge-graph and fact-lookup tools, entity linking and disambiguation, data enrichment, semantic search and research apps. Data is CC0.

api.oanor.com/wikidata-api