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Ask Wol

Your friendly owl for instant OWL ontology reviews: a visual class diagram, namespace and term checks, metadata and documentation review, and a clean-up report.

Or try a well-known ontology
Accepts Turtle, RDF/XML, JSON-LD, N-Triples, or N3.

What do you get?

One HTML report (or JSON via the API) with a section per check, each linked to the matching entry in the modeling guide:

  1. Ontology diagram - an interactive class diagram showing your classes, properties, and inheritance hierarchy. Zoom, pan, and explore.
  2. Ontology metadata - SHACL check on the ontology header: title, description, creator, license IRI, and version are required; created/modified dates and publisher are recommended.
  3. Imports - external vocabularies actually used in your ontology must be declared with owl:imports. Core W3C vocabularies (RDF, RDFS, OWL, XSD) are excluded.
  4. IRI strategy - your ontology’s own defined terms should consistently use either hash (#Term) or slash (/Term), not both.
  5. IRI scheme - each host should be referenced under a single URI scheme. http://example.org/X and https://example.org/X are different IRIs.
  6. Namespaces - fetches each declared namespace URI, checks HTTP status, and tries to parse as RDF (Turtle, RDF/XML, JSON-LD, N-Triples). Falls back to scanning HTML pages for RDF links.
  7. Terms - verifies that terms your ontology references from a remote vocabulary actually exist there. Only terms that appear as subjects are checked. Catches typos like owl:MadeUpClass.
  8. Definition documentation - SHACL check that every internally defined class and property carries both an rdfs:label and an rdfs:comment. Reused external terms are ignored.
  9. Language tag consistency - language-tagged properties like rdfs:label, rdfs:comment, skos:prefLabel, and skos:definition should use the same set of languages across subjects. Catches missing translations and bare strings.
  10. Reasoner checks - lightweight OWL RL reasoning on the current ontology (imports are not followed), reported as three facets: ontology consistency, inconsistent individuals, and unsatisfiable classes.
  11. Unused prefixes - flags @prefix declarations that are never used in any triple. Keeps your ontology tidy.
Owl by E.H. Shepard (1926)

Why “askwol”?

The W3C originally called their language WOL. Tim Finin proposed rearranging it to OWL because “owls are associated with wisdom.” Scrambling three letters is of course what Owl from Milne’s Winnie-the-Pooh is famous for - he spells his own name WOL.

Built by TDCC-NES Ontology Engineers

askwol is developed and maintained by the TDCC-NES Ontology Engineers: Kathrin Füllenbach and Dani Metilli. For questions, collaboration, or support, contact us at nes@tdcc.nl.

Our work is fully funded by Open Science NL. We support ontology selection and reuse, co-development, implementation, knowledge graph design, and training.

External links: TDCC-NES ontology engineers · W3C OWL · OWL 2 Primer