MATH.10:6 - Bias-Annotation
A convenient coordinate can make some changes easy to express and hide others. State what the chosen family reaches before treating its result as a property of all candidates.
A modeler can also import minimization from an allocation problem into a physical action principle. Recover whether the subject requires improvement, an extremum or stationarity; the same variation calculation supports different conclusions under those premises.
For a search procedure, separate a failure to find a better local move from a proof about the full feasible set. This matters when discrete choices or disconnected regions prevent the chosen family from reaching other candidates.