BS PD ISO/TR 20694:2018 gives the general principles for language registers in both descriptive and prescriptive environments. It defines key concepts and describes examples of different language registers that can be applied across all or many languages and those that are language-specific. It lays down guidelines for the use of appropriate language registers needed in a wide range of environments. These include:

terminology work, where it contributes to the development of a wide range of standards;
translation, so that appropriate language levels can be chosen in target languages, to match that of the source language;
lexicography, to improve descriptors of non-geographic language variants;
second language teaching and learning, so that students can avoid pitfalls associated with inappropriate language use;
software, to improve tagging of language variants in computer applications.

Cross References:ISO 639-4ISO 1087-1ISO 24620-1ISO 26162ISO 29383 ISO/TS 11669