34.7. Well-posedness and honest failure🔗

• M20 — Existence and uniqueness on a declared domain. Where a model is inverted, existence and uniqueness are proved on a declared domain — a proof, and a domain the proof is about.

• M21 — Failure outside the domain. What happens outside it. This is the rubric that separates a retrieval that is right where it applies from one that is dangerous where it does not: failure outside the domain must be detected and reported, and ambiguity must be surfaced rather than silently resolved to whichever root the algorithm happened to reach.

• M22 — Conditioning in the contract. The conditioning and quality outputs a consumer needs in order to act on either are part of the declared contract, not a side channel a downstream stage may or may not read.