And given the fact they are systematic, norms apply to the text globally. Nevertheless, the global norm does not saturate necessarily all aspects and dimensions of the text, it only saturates the whole set of occurrences of one particular type of textual unit at least. This is what I call specific saturation of norms. The choice between the singular or the plural form, for instance, normally does not concern all the letters of a word, only the final ones. If every textual norm is per se a systematic textual device, every systematic textual procedure is not per se a norm.
Constraints are pseudo-norms.
Indeed, since a constraint is not less systematic than a norm, it applies to the text following the same logic of specific saturation, i.e., it adds or abolishes or changes one particular type of textual unit at least. When the constraint is anagrammatic, for instance, its application only concerns the letters of the text, but does so in a way that concerns every single letter. Given the difference between constraints and norms, the former can never be a priori tools of written verbal communication. When using constraints, one decides to write this way and this way only. The former designates the text as an accomplished structure, a fixed and invariable object.