Aggregation Interop¶

dag-ml-data owns data-side reducer vocabulary. dag-ml owns coordinator aggregation policy, ML-phase legality, OOF/refit safety and host-controller routing. This page records the 0.2.0 mapping from the data side; it does not change any public schema or ABI signature.

Mapping¶

dag-ml-data reducer	dag-ml coordinator policy	Release behavior
`mean`	`mean`	Directly compatible.
`weighted_mean`	`weighted_mean`	Compatible when a weight column or fit-influence contract is present.
`median`	`median`	Directly compatible.
`vote`	`vote`	Classification-only; both layers reject regression vote tasks.
none	`none`	Coordinator-only mode; no data-side reducer is expected.
`custom`	`custom_controller`	Coordinator routes an aggregation task to a controller and validates result-vs-task identity.
`robust_mean`	not exposed	Data-side only for this release; use `custom_controller` in `dag-ml` until a shared reducer schema is added.
`exclude_outliers`	not exposed	Data-side only for this release; use `custom_controller` in `dag-ml` until a shared reducer schema is added.

Release Rule¶

No implicit mapping may be added during the 0.2.0 release window. If robust_mean or exclude_outliers becomes a first-class dag-ml coordinator method, the change must include:

a shared schema or explicit migration note;
JSON Schema fixture updates in both repositories;
C ABI/Python/WASM contract manifest updates if any public symbol or exported helper changes;
downstream rebuild of chains consuming public signatures.

Signal-Type Replay¶

dag-ml-data exposes signal-type validation helpers. dag-ml does not yet carry an expected signal type through bundle replay. Until that paired contract exists, 0.2.0 documents signal-type replay enforcement as a provider/backlog item rather than a coordinator-enforced invariant.