Every layer declares what it is.

The board

One measure, many contexts

Ten measures compete for a single slot, because two price surfaces drawn on top of each other is a picture nobody can read. Seven context layers may all be on at once, because context is what a measure is read against.

Thirty-two subjects — twenty-four Australian, eight New Zealand — each with six metrics over twenty-four monthly periods from July 2024 to June 2026. Every one of those values is generated. The bands are not evenly covered, and the coverage page states each edge as a quantity rather than leaving it to be inferred.

Absence, declared

Five layers that draw nothing, and say why

A layer with no source behind it is listed on the board with its reason attached, rather than left out of the list. A reader who cannot see that a thing was considered has no way to tell it apart from a thing nobody thought of.

• Building sales history (real)Needs a real sales-history source; none is authorised. The synthetic history above it shows the shape this would take.No source
• AgricultureNeeds a land-use source.No source
• RainfallNeeds a meteorological feed; likely a paid one.No source
• Soil fertilityNeeds a soil-survey source.No source
• PopulationNeeds census data; ABS is CC BY 4.0 and tractable when subjects justify it.No source

Those reasons are the layer's own text, carried from the registry rather than rewritten for this page. Two of them name the obstacle as licensing or cost rather than difficulty, which is the more useful thing to know.

Enforced, not promised

The discipline is in the code

Any project can put a provenance policy in a document. The difference worth paying attention to is whether the policy can be broken by someone who simply forgets it. Three examples, all in the layer registry.

• A layer without provenance cannot registerThe registration function throws rather than warning. A layer that silently rendered without provenance is the exact failure the rule exists to prevent, and a warning is a message nobody reads.Throws
• “Remote” must name the hostA boolean was written first and rejected: it answers whether a layer costs a request and stops there. The field holds the host, so a guard can compare it against the network policy.Throws
• The default layer set is derived, not typedLayers that contact another party are filtered out to produce the defaults, so a future remote layer inherits the exclusion without anyone remembering to add it.Derived

A reader who is told a layer is remote and not told to whom has been told nothing.

The error message the registry raises, verbatim

Traceability

Four links, each citing the last

A number is only as good as the path back to where it came from. Each link is an immutable record that the next one names.

1. ContractA frozen schema. Once published it is never edited, only superseded.
2. SnapshotObservations captured against that contract, at a pinned commit.
3. ChangeThe exact deterministic delta between two snapshots.
4. PreviewA watch read in a browser, computed from files that shipped with it.

The chain is real and the thing flowing through it is not. It carries synthetic observations end to end today, which demonstrates that the mechanism works and demonstrates nothing whatsoever about any property market.

On screen

Panels that cannot be switched off

The board opens with a banner naming everything on it as synthetic, and carries two panels marked REQUIRED — coverage limits, and attribution. They are pinned: there is no toggle that removes them.

The coverage counter states how many layers are measured against how many are invented and how many have no source at all. It is a count rather than a badge, and it moves when the data does. A board that hides its own edges invites a false read, and the edges are the part a buyer most needs.

Layer counts measured by executing the registry at dwelldelta-app v0.10.1, commit 3ecdbf902f0d98e70bc44f1a73e7669fa9ad2112