NOT.1:4.2 - Find cases whose difference changes the work

Construct or recover a pair of cases that require different answers, permitted changes or actions. Explain the difference in the practice before deciding how to write it. Two arrangements of the same components can have different outputs; two performances with the same starting times can have different sustained intervals.

Attempt to express both cases with the candidate notation and its allowed context. If they become indistinguishable while the required answers differ, something needed by that operation has been omitted. Recover it through an expression rule, an accessible annotation, a query to another representation or a narrower declared use. The choice depends on how the expression will be used.

Conversely, two visibly different cases may be interchangeable for the present operation. Keep their shared representation if that simplification preserves the needed result. The question determines which differences matter.

A deliberately unfinished choice can itself matter. If the work permits an unspecified order or duration, retain a way to leave it unspecified and a way to recognize when the next operation needs it settled. A convention that silently chooses a value would change the work being described.