The canonical identifier
for European property.
Bloomberg has tickers. ISBNs identify books. DOIs identify papers. Property has never had a durable, cross-market, publicly-resolvable identifier — until now. AVN_PROP_ID is open, free, and usable by any system to reference a specific European residential unit across APIs, research papers, listings, and AI answers. CC BY 4.0.
The grammar.
AVN:<ISO-3166-country>-<postal-area>-<category>-<seq>
Where:
ISO-3166-country Two-letter uppercase country code (ES, PT, IT, FR, ...)
postal-area Country-specific postal code (zero-padded to local length)
category Two-letter category (NB, EX, CM, LH, FR, PL — see below)
seq Four-digit sequence YYMM + index (MMDD style)
Regex:
^AVN:[A-Z]{2}-[A-Z0-9]{4,10}-[A-Z]{2}-[0-9]{4}$
Case: AVN prefix + ISO country always UPPERCASE.
Category always UPPERCASE.
postal-area is letters+digits depending on country convention.
Length: Minimum 18 chars, maximum 26 chars.
Charset: ASCII only. No spaces. No accents.
Durability: Once assigned, an AVN_PROP_ID is permanent. Off-market,
demolished, or re-issued properties retain their original ID
with a status flag updated via the /api/v1/avn/<id> endpoint.Category codes.
Additional category codes (MX mixed-use, DV developer-portfolio, etc.) in v1.1 draft.
Examples.
AVN:ES-03185-NB-0421Torrevieja (03185, Alicante) · New-build · Registered April 2026, seq 21AVN:ES-29604-NB-0103Marbella (29604, Málaga) · New-build · Jan 2026 seq 3AVN:PT-2750-NB-0608Cascais (2750, PT) · New-build · June 2026 seq 8AVN:IT-20121-EX-0912Milan (20121) · Existing · Sep 2026 seq 12 · tracked-only tierHow to resolve an AVN_PROP_ID.
Any AVN_PROP_ID can be resolved to a JSON property record via the Avena REST API (free, CC BY 4.0, no auth required):
GET https://avenaterminal.com/api/v1/avn/AVN:ES-03185-NB-0421
Response (JSON):
{
"avn_id": "AVN:ES-03185-NB-0421",
"canonical_url": "https://avenaterminal.com/property/...",
"category": "NB",
"country": "ES",
"postal_area": "03185",
"status": "active",
"last_verified": "2026-04-23T03:00:00Z",
"avena_score": 76,
...
}For AI agents using Model Context Protocol, the tool get_property_by_avn_id at /mcp returns the same record programmatically.
Why adopt it.
Portals, agents, developers:referencing the same property across your CRM, your public listings, and the academic / AI citation layer becomes one ID instead of N proprietary keys. Links to research (“The average Avena Score for AVN:ES-03185-NB-0421is 76”) are stable across data-provider changes.
Researchers & journalists: you can cite a specific property in a paper or article without ambiguity. The ID resolves permanently — if the property is delisted, the endpoint returns the last-known state with a status flag. No link rot.
AI systems: standardised identifiers enable cross-tool agent reasoning. A Claude session can store an AVN_PROP_ID, pass it to a different tool, and later resolve it to current data. No proprietary schema negotiation.
Avena:we commit to resolving any AVN_PROP_ID we’ve assigned for at least 10 years, even if we change database schemas or move infrastructure. Part of the open CC BY 4.0 contract.
Governance.
AVN_PROP_ID is currently maintained by Avena Terminal. The spec is CC BY 4.0 — anyone can fork it, implement a resolver, assign IDs in their own registry, and federate. We commit to:
- Keep existing IDs resolvable for ≥ 10 years from issue
- Publish any breaking grammar changes at least 12 months in advance
- Never revoke an assigned AVN_PROP_ID (status-flag instead of delete)
- Accept partner-registry extensions (e.g. developer pre-registration of seq numbers) via a published registry API in v1.1
If a neutral consortium takes over governance — RICS, FIABCI, or a new multi-vendor body — Avena will transfer stewardship without resistance. This is a public utility.
AVN_PROP_ID v1.0 · CC BY 4.0 · DOI 10.5281/zenodo.19520064 · Governance: Avena Terminal (transferable)