This proposal is part of the 2.03 upgrade process, please comment by replying below.
Activity and Organisation
All uses of @xml:lang attribute
Type of Change
Xml:lang references the generic XML spec which allows for a range of languages, locales, regions and scripts. It is used in our schema with a more limiting definition - specifying sole use of ISO 639-1. This is not enforceable. Moreover, there are users who need to specify languages that aren’t on the ISO 639-1 list, but can be specified with BCP 47.
Change all definitions of xml:lang
ISO 639-1 code specifying the language of text in this element.
A code specifying the language of text in this element.It is recommended that wherever possible only codes from ISO 639-1 are used.