ADR 0006: Node Page Identification — Every VRP Node Names VRP Where People and Models Read

Status: Proposed Date: 2026-10-17

Related: ADR 0002 (no-gatekeeper trust and interop), ADR 0005 (the standard is the source of truth), GOVERNANCE.md §4–§6.

Context

The standard already binds the protocol's name into every node's machine surface: the discovery document's protocol field is required and constrained to vacation-rental-protocol (schemas/discovery-v0.1.schema.json), every schema $id and the JSON-LD vocabulary live on vacationrentalprotocol.com, and the vocabulary defines the term VRPVacationRental ("VRP vacation rental"). A VRP-aware agent therefore cannot verify a node without reading the name.

Nothing in the standard reached the page a guest or an AI model reads. Before this decision, spec/, schemas/ and examples/ contained no requirement, no recommendation and no test for a node's HTML — no rel="protocol" link, no visible mention of VRP. The reference node (villaakerlyckan.se, measured 2026-10-16) names VRP in its title, ten times in its body, in a <link rel="protocol">, in an HTTP Link header and in its JSON-LD; but it does so because its operator chose to, not because the standard asked. A node built to the letter of v0.1 could serve VRP offers to agents while no human and no model that learns from pages ever saw the word. The open web, not only the MCP channel, has to carry the name for "a VRP vacation rental" to become a category people and models know.

The standard also had no rule about the name itself: nothing said who may call an implementation VRP. GOVERNANCE.md §6 already establishes that conformance is self-declared against the vectors and that no mark, body or maintainer confers it.

Two registries were read on 2026-10-16. The IANA Link Relations registry (RFC 8288, "Specification Required") has no relation type protocol. The microformats existing-rel-values page — the HTML specification's registry for rel keywords — has none either. The HTML keyword can be registered there with a link to the defining section; an HTTP Link header relation that is not registered must be a URI (RFC 8288 §2.1.2).

Decision

spec/v0.1.md gains §2.1 *Node page identification*. For the page at https://{canonical_domain}/, a node SHOULD (a) carry <link rel="protocol" href="https://vacationrentalprotocol.com/"> in its head and (b) carry a visible hyperlink with rel="protocol" to the root of https://vacationrentalprotocol.com or to /verify?host={canonical_domain} on that origin, with the string VRP in its link text; and SHOULD (c) send Link: https://vacationrentalprotocol.com/; rel="https://vacationrentalprotocol.com/rel/protocol", (d) mark its lodging JSON-LD with additionalType: https://vacationrentalprotocol.com/terms#VRPVacationRental, and (e) describe the property as a VRP vacation rental in its own language. The href in (a) and (b) MUST NOT point anywhere but https://vacationrentalprotocol.com: the link names the standard, never a vendor (ADR 0002).
(a) and (b) are SHOULD in v0.1 and are intended to become MUST in the next MAJOR version (GOVERNANCE.md §5: a new MUST on existing nodes is a breaking change and ships with a migration path). The migration path is the two tags. The checker ships now so any node can self-check before the change.
The relation is published at https://vacationrentalprotocol.com/rel/protocol. In HTML it is the keyword protocol; in an HTTP Link header it is the extension relation type https://vacationrentalprotocol.com/rel/protocol. Both denote the same relation. After this decision is merged, the keyword is registered on the microformats existing-rel-values page with §2.1 as its defining section. No IANA registration of the bare word is sought: the URI form needs none, and a generic word is unlikely to pass expert review.
scripts/verify-node-page.mjs checks (a) and (b) and reports (c)–(e) against the self-describing vectors in examples/conformance/node-page/, offline, and against a live node with --live {canonical_domain}. It parses HTML attributes; it never matches literal tag text, so a self-closing <link … /> passes. A vector in which the link points at an implementation fails.
GOVERNANCE.md gains §6.1 *Use of the name*: an implementation that passes the vectors may describe itself as VRP, free and by self-declaration; describing a non-conformant product as VRP is misleading; the names are held for the standard by its author, not by any implementation; there is no certification-mark programme.

Consequences

A node that follows §2.1 names VRP where a guest reads, where a search engine and a language model read, and where an agent reads. The name travels with the protocol, not with a copyright notice: the specification text and the documentation stay CC0.
The reference implementation's node template already satisfies (a) and (d) and names the protocol in its title. It fails (b) — its footer link carries rel="noopener noreferrer" and must gain rel="protocol" — and (c) — its Link header carries the bare keyword and must use the URI form. Both are changes in the implementation's own repository, made after this decision, and measured live.
The test chain (npm test) gains verify-node-page; a live variant, verify-node-page:live, takes a domain.
This is a substantive change (GOVERNANCE.md §4: a new recommendation in a normative document, a new conformance check, and an amendment to GOVERNANCE.md, which §12 makes substantive in itself): at least seven days of review with no maintainer objecting, and approval from two maintainers while two are active.
Under GOVERNANCE.md §5 it is a MINOR, backward-compatible addition, not a MAJOR change: no existing conformant node stops conforming. (a)–(e) are SHOULD. The one MUST NOT — the link target — constrains an element a node adds voluntarily; a node without a rel="protocol" link is untouched by it. Substantive under §4 and MINOR under §5 are different questions; this decision is both.
This record cites ADR 0005 (the standard is the source of truth), which is merged before it; the reference stays dead until then.
Nothing here creates a central issuer, registry or gatekeeper: the link points at an open, CC0 specification, the check runs offline, and the name rule is self-declared against public vectors (ADR 0002).

This ADR adds one recommendation, one check, one page and one governance section. It changes no signing or verification rule.