# T-02: Provenance & Quality Layer
## T-02: Provenance & Quality Layer
**W3C PROV-O**
The W3C Provenance Ontology. Every data submission, validation event, and agent action is recorded as a PROV-O graph: `prov:Entity` (the data), `prov:Activity` (what happened), `prov:Agent` (who did it), `prov:wasGeneratedBy`, `prov:wasAttributedTo`.
**ISO 8000-220:2025 — Data Quality**
International standard for data quality management. Used for metadata quality dimensions: completeness, accuracy, consistency, timeliness. CTH maps these to field-specific thresholds in the SHACL profile.
**cth:FieldDataQuality SHACL Profile (CTH-original)**
SHACL shapes that enforce EUDR-specific and Andean-specific quality rules at ingestion. Key shapes:
| Shape | Rule | Rationale |
|---|
| cth:GpsPrecision | Polygon vertices must have ≥6 decimal place precision | EUDR Article 9 requires parcel identification; 5dp = ~1m accuracy; 6dp = ~10cm |
| cth:DeforestationDataVintage | IDEAM reference raster must be ≤24 months old | EUDR requires current deforestation status; stale data invalidates DDS |
| cth:IotCalibration | IoT soil/weather sensors must have calibration certificate ≤180 days old | Sensor drift; CSRD ESRS E4 requires traceable measurement |
| cth:AndeanGpsLock | GPS receiver must record ≥90 second lock wait per polygon vertex | Mountain terrain + tree canopy causes GPS multipath error; 90s reduces error below EUDR threshold |
### Ledger Integrity
The governance ledger is an append-only Postgres table with rolling SHA-256 hashes. Each entry hashes the previous entry's hash (blockchain-like chain). KERI (Key Event Receipt Infrastructure) anchoring is used for cross-organisational verifiability — validators can independently verify ledger integrity without trusting CTH's infrastructure.