# Task 14 — Export: RDF (Metadata & Provenance Graph)

## Goal
RDF surface for the metadata/provenance layer only — never the numeric series (per ADR).

## Input
- `canonical/` snapshot headers + hierarchy, `schema/`, lineage.

## Actions
1. Mint stable IRIs for every data note, batch, coupon, sample, measurement (pattern `https://tribology.ufl.example/id/<entity>/<key>`; base IRI in config).
2. Write `scripts/export_rdf.py` → `exports/rdf/metadata.ttl` (Turtle): hierarchy, measurement headers, atmosphere, instrument, source-file provenance. Vocabularies: PROV-O (provenance), QUDT (units), Dublin Core (citation), DCAT (dataset catalog), local `lab:` terms.
3. Emit `exports/rdf/mappings.r2rml.ttl` — R2RML mappings from the PostgreSQL schema, ready for Ontop virtual deployment.
4. Numeric series: reference-only — each measurement IRI carries a `lab:dataService` pointer, no point triples.

## Intermediate Result (done when)
- `metadata.ttl` parses (validate with `rdflib`); triple counts reported per class.
- R2RML mappings cover all metadata tables. `EXPORT_MANIFEST.json` written.
