Channel

Meaning

A Channel answers which independently usable part of a Provider is being selected. A Provider may expose one channel or several channels with distinct endpoints, variables, forecast levels, or delivery modes.

Owns

default is 0, including legacy saved snapshots, meaning no expiry. Observations use the newest available frame at or before now; forecasts use the closest valid time, retaining the final available frame after forecast coverage ends. Positive values require a frame within that many seconds of now. Explicit historical cursor selection keeps the Channel's temporal coverage policy. Acquisition does not overwrite this column. It does not change object-event filters (such as recent fires) or refresh schedules. The channel editor shows hours; the database validates nonnegative whole seconds.

nominal sensor pixel. Unknown values stay absent, and approximate values are explicitly marked instead of inferred from delivery zoom or tile size.

diagnostic is stored separately from that machine state.

• A provider-local immutable export_key used by portable map recipes.
• Endpoint and delivery semantics.
• Poll or refresh cadence when applicable.
• latest_max_offset_seconds: a separate display window for Now/Latest. The
• Rendering contract and supported presentation capabilities.
• Validated static technical facts such as declared data-grid resolution or a
• Channel-specific attribution overrides.
• A typed snapshot outcome (ok, error, or no result yet); the bounded safe

Map binding

One selected Channel normally creates one Layer. Compatible vector snapshot channels can be intentionally composed, but the selected subset remains explicit and stable for the existing map.

Composition is source-local: channels that share a Provider may declare a stable provider identity key and deterministic priority. The delivery path then emits one feature, merges their properties, and takes geometry from the highest-priority matching channel. This supports bounded presentation Providers such as canonical volcano positions enriched with an aviation advisory. It does not reconcile arbitrary records across independent Providers; raw channel rows and their source attribution remain preserved.

Boundaries

Runtime status, active versions, counters, errors, and heartbeat timestamps are live database state. They must not be manually mirrored in this bundle.

Large snapshot acquisition may stage bounded batches incrementally, but a Channel exposes only the previous committed version until one final atomic publication. Failed partial imports are never part of map read paths.

For numeric raster Channels, rendering metadata follows the numeric raster encoding rule: the Channel owns codec, range, validity, quantity, and unit, but never the color palette. Inspectable raster fields follow the shared raster pixel inspection rule: Fields, hover, and details derive from the same pixel_delivery capability.

An on-demand raster Channel may also declare queryable raster periods. Availability, exact-period support, cumulative support, and the default belong to Channel. A Map Connection may select a bounded subset; the viewer's current cursor belongs to neither.