The Feature Registry is a centralised reference documenting every feature used in the model, its definition, its source, its proxy variable assessment, and its lineage to source data. It serves as a single point of reference for reviewers, auditors, and the internal team.

For each feature, the registry records the feature name and description, the source dataset and field, the transformation applied to derive the feature (referencing the lineage records), the proxy variable assessment (correlation with each protected characteristic, the justification review outcome from Article 74, and the retention or removal decision), the feature importance (SHAP-based or permutation importance) in the current model version, and any fairness-related observations (such as the feature contributing disproportionately to predictions for specific subgroups).

The registry is maintained as a living artefact, updated whenever features are added, removed, or modified. Feature store tools (Feast, Tecton, Hopsworks) can partially automate the registry by centralising feature definitions and metadata. For organisations without feature store infrastructure, a structured spreadsheet or database provides the minimum viable registry.

Key outputs

• Feature Registry (complete, covering all model features)
• Proxy variable assessment per feature
• Version tracking for registry updates