owlcompare

Modern semantic ontology diff. See what actually changed.

owlcompare compares two OWL/RDF ontologies and produces an interactive HTML report (plus JSON, Markdown, and CI-friendly outputs) that surfaces meaningful changes — not just raw axiom additions.

Status

Pre-alpha. Under active development. See docs/ROADMAP.md for progress.

Why

Existing ontology diff tools (ROBOT, owl-diff, Protégé compare) operate at the axiom level. A simple refactor produces hundreds of axiom-level changes that don't tell you whether the semantics actually changed. owlcompare diffs at four semantic layers — syntactic, structural, inferential, and impact — and presents the result in a UX built for humans reviewing pull requests.

Quick start (planned)

uv tool install owlcompare
owlcompare diff old.ttl new.ttl --out report.html

Use with GitHub Actions

Diff your ontology on every pull request in three lines:

- uses: actions/checkout@v4
- uses: phelz/owlcompare@v1
  with:
    ontology-path: ontology/my-ontology.ttl

You get a PR comment with the diff, the HTML and JUnit reports uploaded as artifacts, and a check that fails on breaking changes. See docs/github-action.md for the full reference — inputs, outputs, baseline detection, and more examples.

Documentation

• Project brief — vision, audience, success criteria
• Architecture — components, data flow, public surfaces
• Roadmap — phased delivery plan
• Design decisions — why we chose what we chose
• Conventions — code style and project standards
• Glossary — terminology used consistently

License

MIT — see LICENSE.