D059 - A third kind of record: measurements, which assert nothing

Status: decided, on the user's suggestion, correcting a limitation in the earlier design.

Every record until now carried a judgement, and a judgement needs an expectation. Where a document supplies one that is spec; where nobody does, this project supplies it and marks it assumed.

There is a third option and this program did not have it: record what happened and assert nothing. A duration is a fact. It needs no expectation and does not go stale when a guess turns out wrong.

The earlier objection - that timing a sleep means picking a threshold, and picking one is inventing a specification - was aimed at the wrong thing. It argues against asserting on a measurement, not against recording one. OBS|measure records carry a quantity, a value and a unit, and no verdict.

Assertions stay. A loose bound marked assumed is still worth having, because it is correctable and because "no expectation at all" is not a stronger position than "a stated guess". What changes is that the number sits beside the verdict, so correcting the guess from hardware is reading a figure and editing a constant rather than re-deriving what the expectation should have been.

The measurement is the calibration. Forty-seven checks are assumed and none is hardware. That is the ratio a console visit has to move, and a measurement makes each move cheap and unambiguous.