Methodology papers, identifier standards, and public trackers published by VDG. Each is citable, version-stable, and free to reference. Underlying data history and API access are licensed separately.
VDG publishes its methodology openly so institutional readers can verify and cite. Every score AirIndex publishes ties to source documents through AIX-IDs; the methodology paper describes how the identifiers are minted, how succession is handled, and how the reference resolver works.
The pattern follows the precedent set by financial-data peers. Bloomberg publishes its Open Symbology (FIGI); Moody's and S&P publish rating criteria and methodology papers. The moat isn't secrecy — it's the accumulated historical record + operational discipline + the citation surface itself.
New standards graduate to this page as they're published. Methodology refinements arrive as versioned successors of prior papers (e.g. v1.3 → v1.5), with the succession chain visible to readers.