Stuart Yeates <[log in to unmask]> wrote:
My biggest issue (that's not covered in the doc, but which I've already fed to the doc's authors) is that BIBFRAME mandates three-letter language codes, where available, while core RDA mandates two-letter language codes, where available.

To my knowledge, RDA has no such instruction.  There is RDA 7.13.2 (Script), where we're told to "expression the language content of the resource using one or more of the terms from ISO 15924..." (mentioned also under 0.12).

There's also LC-PCC PS, which points to the MARC language code list for terms rather than codes:

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