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🦉 Ask Wol Beta

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.

What do you get?

An interactive class diagram of your ontology, plus one HTML report (or JSON via the API) with a section per check. The checks are grouped into five areas, and each links to the matching entry in the publishing guide:

1. Ontology basics

• 1.1 Ontology metadata: a SHACL check on the ontology header: title, description, creator, and version are required; created and modified dates and publisher are recommended.
• 1.2 Imports: every owl:imports target declared in the ontology header is fetched over HTTP and parsed as RDF, the same way a reasoner would follow it.
• 1.3 IRI strategy: the ontology's own defined terms should consistently use either hash (#Term) or slash (/Term), not both.
• 1.4 IRI scheme: each host should be referenced under a single URI scheme. http://example.org/X and https://example.org/X are different IRIs.
• 1.5 Open license: the declared dcterms:license (or schema:license) must be an open license per the Open Definition; CC0 and CC BY are recommended, other open licenses (e.g. CC BY-SA, ODC-By, ODbL) pass with a warning, and a missing or non-open license fails.

2. Namespaces & reuse

• 2.1 Namespaces: fetches each declared namespace URI, checks HTTP status, and tries to parse it as RDF (Turtle, RDF/XML, JSON-LD, N-Triples). Falls back to scanning HTML pages for RDF links.
• 2.2 Unused prefixes: flags @prefix declarations that are never used in any triple.
• 2.3 External term definitions: verifies that terms reused from an external vocabulary actually exist there. Catches both typos (foaf:nme) and made-up terms (owl:MadeUpClass). A term that exists but is marked deprecated upstream is flagged as a warning.

3. Term structure

• 3.1 Internal term definitions: flags terms in the ontology's own namespace that are referenced but never defined. Usually a typo or a forgotten declaration.
• 3.2 Term inventory & naming: categorizes every internal term (class, object property, datatype property, datatype, individual) and checks capitalization: classes start uppercase, properties lowercase. Coded identifiers are exempt.
• 3.3 Domains & ranges: every internally defined object and datatype property should declare a domain and a range. Object properties range over classes; datatype properties over datatypes.
• 3.4 Datatypes: datatypes used as property ranges and literal datatypes should be recognized XSD built-ins, rdfs:Literal, rdf:langString, or a locally declared rdfs:Datatype. Catches typos like xsd:stirng.
• 3.5 Non-ontology terms: an OWL ontology defines schema (classes, properties, datatypes). A skos:Concept scheme is subject-matter data, not schema, and belongs in a separate resource. Named individuals are not flagged.

4. Term documentation

• 4.1 Labels: a SHACL check that every internally defined class and property carries an rdfs:label.
• 4.2 Comments: a SHACL check that every internally defined class and property carries an rdfs:comment.
• 4.3 Language tag consistency: labels and definitions (rdfs:label, rdfs:comment, skos:prefLabel, skos:definition, ...) on internally defined terms should use language tags consistently.

5. Logic

• 5.1 Reasoner checks: lightweight OWL RL reasoning on the current ontology only (owl:imports are not followed), with three facets: ontology consistency, inconsistent individuals, and unsatisfiable classes.

What you don’t get: askwol checks syntax and structure, but not content or meaning, which is what ontologies are all about.

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, as Dave de Roure first pointed out to the working group.

About

askwol is developed and maintained by the TDCC-NES Ontology Engineers (Kathrin Füllenbach and Dani Metilli), funded by Open Science NL. We help with ontology selection and reuse, co-development, knowledge graph design, and training.

askwol is free and open source under the MIT licence. It is currently in beta: some checks may be incomplete or produce false positives. Found a bug or have an idea? Open an issue on GitHub or reach us at nes@tdcc.nl.

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