D478 - A differential result is its own knowledge tier

Status: assumed Date: 2026-09-02

A fact confirmed by running the same call against a published implementation of the same interface, rather than against the target itself, is recorded under its own tier, distinct from measured, published, guest-observed and assumed, and it names which implementation it ran against.

Why: a differential result establishes agreement with another implementation, not that the target behaves the same way. Conflating it with a hardware measurement would inflate the count this project uses to know how much of itself is unverified against real hardware.

Rejected:

• Recording it as measured: it was not observed on the target and would misstate what the measured count means.
• Recording it as published or assumed: too coarse, and discards that something was actually executed and agreed.