For the purposes of tagging language resources By language, when a language code for a sign language is used is the default assumption that the language resource is in the visual/video modality, rather than the textual format? Or is BCP-47 agnostic to these assumptions of modality? For the purposes of ANIA repository of tags, is there a specified suffix for the written modality of sign languages?

What is the case for Brail? Is there a script tag for brail? (Yes there is). But the orthographic representation in brail is still ambiguous.