Aggregation Interop¶

dag-ml and dag-ml-data intentionally own different parts of aggregation:

dag-ml-data describes data-side reducer vocabulary and validates reducer-shaped payloads.
dag-ml owns ML-phase safety, OOF/refit legality, prediction levels, custom-controller routing and leakage-sensitive aggregation execution.

This document is the 0.2.x RC mapping. It is documentation-only and does not change any public schema or ABI signature.

Mapping¶

dag-ml coordinator policy	dag-ml-data reducer	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_controller`	`custom`	Coordinator routes an aggregation task to a controller and validates result-vs-task identity.
not exposed	`robust_mean`	Not a final-release coordinator mode; use `custom_controller` until a shared reducer schema is added.
not exposed	`exclude_outliers`	Not a final-release coordinator mode; use `custom_controller` until a shared reducer schema is added.

Release Rule¶

No implicit mapping may be added during the 0.2.x RC 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.x documents signal-type replay enforcement as a provider/backlog item rather than silently accepting it as a supported coordinator invariant.