This identifier must be unique when the rule is part of a ruleset. The identifier can be any text [...]
To know if an identifier is unique (and to be able to use it in one rule to point to another), you need to know when two identifiers are the same. E.g., are capital letters (ABC) the same as lowercase letters (abc)? If a letter can be encoded in Unicode in two ways (e.g., ‘é’ as single character vs separate ‘e’ + acute accent) are those the same?
(This is part of the review by the Internationalization WG. Sorry for being late – it's entirely my fault.)
4.1. Rule Identifier https://www.w3.org/TR/2024/WD-act-rules-format-1.1-20240618/#rule-identifier
To know if an identifier is unique (and to be able to use it in one rule to point to another), you need to know when two identifiers are the same. E.g., are capital letters (ABC) the same as lowercase letters (abc)? If a letter can be encoded in Unicode in two ways (e.g., ‘é’ as single character vs separate ‘e’ + acute accent) are those the same?
‘Character Model for the World Wide Web: String Matching’ explains the issues with comparing two strings of text and has recommendations for choosing an algorithm, including for text strings used as identifiers.