A maturity model for open data, proposed by Tim Berners-Lee, ranging from one star (any format with an open licence) to five stars (linked data with URIs).
The five star model provides a practical roadmap for improving open data quality:
- ★ Available on the web with an open licence (any format, including PDF)
- ★★ Available as structured, machine-readable data (e.g., Excel)
- ★★★ Available in a non-proprietary open format (e.g., CSV)
- ★★★★ Uses URIs to identify things, so others can link to it
- ★★★★★ Links to other data to provide context (Linked Data)
Example: A city publishes its park locations as a PDF map (one star). Upgrading to a CSV file (three stars) makes the data machine-readable and reusable. Publishing as GeoJSON with stable URIs for each park (four stars) allows other datasets to reference individual parks directly.
Most open data programs aim for three stars as a practical minimum. Four and five stars require additional infrastructure but significantly increase the data's value for integration and discovery.