Open Ontologies

Open Ontologies is a Rust MCP (Model Context Protocol) server and desktop Studio for AI-native ontology engineering. It exposes 70+ tools that let an LLM client build, validate, query, diff, lint, version, reason over, align, plan, certify and govern RDF/OWL ontologies against an in-memory Oxigraph triple store. It ships as a single binary with no JVM and no Protege dependency, and covers OWL 2 profile checking, SHACL validation, SPARQL, OWL-RL reasoning, ontology diffing, a marketplace of 33 standard ontologies, IES (Information Exchange Standard) support for UK defence and government data, semantic embeddings, PDDL planning, and a full lineage audit trail. The design is deliberately MCP-native: the server provides validation, scaffolding and proof, while the connected model supplies the intelligence. There are no embedded LLM clients, no API keys and no provider lock-in, so the same engine runs offline and in air-gapped environments. Open Ontologies is the verification engine behind a public programme of register-integrity audits, where every published finding is re-checked by an independent path before release. Funding supports maintenance, cross-platform release engineering, the reasoning and planner layers, and continued free distribution.