Yet Another Great Ontology
Large semantic knowledge graph from Wikipedia, WordNet, Wikidata. 17M+ entities, 150M+ facts with high precision.
Visit WebsiteBrowse the tree, filter it, or click any class to see just its corner of it.
Where this one tends to earn its keep.
High-precision knowledge base for QA systems
Entity disambiguation in text
Fact verification and validation
Academic NLP research
I haven't checked this label against the actual licence text — it's the catalogue's original guess. Check the ontology's own site before you rely on it.
Others worth a look in Knowledge Graphs.