Metering

How delivery events are projected into the metered units that contracts are denominated in.

Metering is the projection from raw delivery events into the metered units a contract is denominated in: impressions, dwell seconds, surface-hours, attention seconds, message sends, render opportunities.

Why projection, not aggregation

A delivery event is the source of truth. The metered unit is a projection — derived from the event, not stored alongside it. Two properties follow:

1. Re-projectable. Given the same delivery events and the same projection rules, the metered units are bit-identical. This is how the auditor checks the platform’s numbers.
2. Versioned. When the projection rules change (e.g. a new IAB viewability standard), we version the rule set and reproject historical data. Old rules are kept reachable for compliance audit.

Substrate-specific projection rules

Each substrate has its own projection rules. The headline ones:

Substrate	Metered unit
DOOH	Impressions × surface attention factor
CTV	Impressions (qualified by IAB definition)
MOBILE	Render opportunities + dwell
GAMING	Viewability seconds per IAB Gaming SIG 2024
AUTOMOTIVE	Dwell, gated by vehicle speed
AUDIO	Listen-through seconds, gated by AudioAttentionConstraint
MESSAGING	Sends, gated by OptOutRegistryConstraint
DRONE / ROBOTICS	Surface-hours, with airspace / kinematic gating
SATELLITE	Beam-footprint-hours

The full rule set lives in packages/sdks/auditor-ts/src/metering/ and ships with every release of the auditor — so a regulator can reproject historic packs offline.

Settlement

Metered units feed settlement. Until the auditor confirms that the metering projection is bit-identical, the settlement number is not legally final.