ontology-engineering

name	ontology-engineering
description	Build, validate, and govern RDF/OWL ontologies using the Open Ontologies MCP server. Use when the user asks to create, modify, query, or manage ontologies, knowledge graphs, or RDF data. Use when this capability is needed.
metadata	{"author":"fabio-rovai"}

Ontology Engineering Workflow

You have access to the Open Ontologies MCP server, which provides 50+ tools for AI-native ontology engineering backed by an in-memory Oxigraph triple store.

Core Workflow

When building or modifying ontologies, follow this workflow. Decide which tools to call and in what order based on results -- this is not a fixed pipeline.

1. Generate

• Understand the domain requirements (natural language, competency questions, methodology constraints)
• Generate Turtle/OWL directly -- you know OWL, RDF, BORO, 4D modeling natively

2. Validate and Load

• Call onto_validate on the generated Turtle -- if it fails, fix syntax errors and re-validate
• Call onto_load to load into the Oxigraph triple store. For repos that mount a folder of .ttl files via [general] ontology_dirs, prefer onto_repo_load so the same compile-cache / TTL-eviction path is exercised. Use onto_repo_list to discover candidate files.
• Call onto_stats to verify class count, property count, triple count match expectations

3. Verify

• Call onto_lint to check for missing labels, comments, domains, ranges -- fix any issues found
• Call onto_query with SPARQL to verify structure (expected classes, subclass hierarchies, competency questions)
• If a reference ontology exists, call onto_diff to compare

4. Iterate

• If any step reveals problems, fix the Turtle and restart from step 2
• Continue until validation passes, stats match, lint is clean, and SPARQL queries return expected results

5. Persist

• Call onto_save to write the final ontology to a .ttl file
• Call onto_version to save a named snapshot for rollback

Cache and Multi-Ontology Loading

The server keeps a single active ontology in memory plus an on-disk N-Triples compile cache for everything it has parsed. Switch between several ontologies without paying re-parse costs:

• onto_repo_list — enumerate .ttl / .owl / .nt / .rdf / .nq / .trig / .jsonld files configured under [general] ontology_dirs. Container-friendly: mount a host folder of TTL files and discover them at runtime without hardcoded paths.
• onto_repo_load — load by bare file stem, relative path, or absolute path inside a configured repo dir. Reuses the same compile-cache / TTL-eviction path as onto_load.
• onto_cache_status / onto_cache_list — inspect what is cached, what is currently active, and the effective [cache] configuration (TTL, auto_refresh, dir).
• onto_cache_remove — drop a cached entry by name (pass delete_file=false to keep the on-disk N-Triples for a later reload).
• onto_unload — drop the active ontology (or a specific cached entry by name) from memory; the on-disk cache is preserved unless delete_cache=true.
• onto_recompile — force a re-parse from source, ignoring the cache. Without name, recompiles the active ontology and reloads it; with name, rebuilds a non-active entry without disturbing the active in-memory store.

Ontology Lifecycle (Terraform-style)

For evolving ontologies in production:

1. Plan — onto_plan shows added/removed classes, blast radius, risk score. Check onto_lock for protected IRIs.
2. Enforce — onto_enforce with a rule pack (generic, boro, value_partition, hierarchy) checks design pattern compliance.
3. Apply — onto_apply with mode safe (clear + reload) or migrate (add equivalentClass bridges).
4. Monitor — onto_monitor runs SPARQL watchers with threshold alerts. Use onto_monitor_clear if blocked.
5. Drift — onto_drift compares versions with rename detection and self-calibrating confidence.
6. Lineage — onto_lineage shows the full plan → enforce → apply → monitor → drift trail for the current session.

Data Extension Workflow

When applying an ontology to external data:

1. onto_map — generate mapping config from data schema + loaded ontology
2. onto_ingest — parse a structured file (CSV, JSON, NDJSON, XML, YAML, XLSX, Parquet) into RDF
3. onto_sql_ingest — run a SQL query against PostgreSQL or DuckDB (via postgres://, duckdb:///path.duckdb, :memory:, or a *.duckdb file path) and ingest result rows. Use this when the source data lives in a database, or when you want to use DuckDB as a federation layer over remote Parquet/CSV/JSON via the httpfs, postgres_scanner, iceberg, etc. extensions.
4. onto_import_schema — introspect a PostgreSQL or DuckDB schema and generate OWL classes/properties/cardinality from tables/columns/PKs/FKs.
5. onto_shacl — validate against SHACL shapes
6. onto_reason — run RDFS or OWL-RL inference
7. Or use onto_extend to run the full file-based pipeline (ingest + SHACL + reason) in one call

Reasoning and DL Explanation

• onto_reason — RDFS / OWL-RL forward-chaining materialisation
• onto_dl_check — check subClass ⊑ superClass using DL tableaux
• onto_dl_explain — return the clash trace explaining why a class is unsatisfiable

Semantic Search and Embeddings

After loading, generate embeddings to enable natural-language search:

• onto_embed — generate text + Poincaré structural embeddings for every class. Honours [embeddings] provider = "local" | "openai" and the OPEN_ONTOLOGIES_EMBEDDINGS_* env vars.
• onto_search — natural-language query → most-similar classes (mode: "text" | "structure" | "product").
• onto_similarity — compute cosine + Poincaré distance between two specific IRIs.

When embeddings exist, onto_align automatically uses them as a 7th alignment signal, catching semantically equivalent classes whose labels differ.

Tool Reference

Tool	When to use
onto_status	Check that the server is running and how many triples are loaded
onto_validate	After generating or modifying Turtle -- always validate first
onto_load	Load Turtle/N-Triples/RDF-XML into the triple store
onto_stats	Sanity-check class / property / triple counts
onto_lint	Catch missing labels, comments, domains, ranges
onto_query	Verify structure, answer competency questions
onto_diff	Compare against a reference or previous version
onto_save	Persist the active ontology to a file
onto_convert	Convert between Turtle, N-Triples, RDF/XML, N-Quads, TriG
onto_clear	Reset the in-memory store
onto_pull	Fetch ontology from a remote URL or SPARQL endpoint
onto_push	Push triples to a SPARQL endpoint
onto_import	Resolve and load owl:imports chains
onto_marketplace	Browse / install standard ontologies from the curated catalogue
onto_version	Save a named snapshot before making changes
onto_history	List saved snapshots
onto_rollback	Restore a previous snapshot
onto_unload	Drop the active (or named) ontology from memory
onto_recompile	Re-parse the source, ignoring the on-disk compile cache
onto_cache_status	Inspect compile cache: active slot, all entries, [cache] config
onto_cache_list

Key Principle

Dynamically decide the next tool call based on what the previous tool returned. If onto_validate fails, fix and retry. If onto_stats shows wrong counts, regenerate. If onto_lint finds missing labels, add them. The MCP tools are individual operations -- you are the orchestrator.

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Source: fabio-rovai/open-ontologies — distributed by TomeVault.