NOT.1:10 - Architectural Rationale

A notation provides ways to form and use expressions. What to support depends on what the user needs to obtain or change. Starting with that operation connects the subject matter, reader preparation and representation without making any one of them a substitute for the others.

Contrasting cases make an omitted distinction consequential. If two cases with the same available representation require different answers, a reader using only that representation cannot be guaranteed the right answer in both. The design must recover the difference, obtain additional information or accept the resulting limitation. This argument identifies a requirement; trying the supported operation is still needed to learn whether the candidate is usable at the available effort.

The pattern chooses requirements through small constructive trials. NOT.2-.4 develop formation, interpretation and transformation rules. A.6.3.RT.OE addresses a different starting condition: the scheme is available and an operative expression must be built under it. C.2.8 characterizes what a prepared observer can extract; the present method uses that question to construct or choose a scheme. These contributions can be combined without making notation design a compulsory step in every reading task.