I noticed just now the publication of XML 1.0 4th Edition. In it I
notice a few issues with the handling of language tags (a topic in which
I take some interest).
In particular, I note:
1. Section 1.1 contains this paragraph:
This specification, together with associated standards (Unicode
[Unicode] and ISO/IEC 10646 [ISO/IEC 10646] for characters, Internet RFC
3066 [IETF RFC 3066] for language identification tags, ISO 639 [ISO 639]
for language name codes, and ISO 3166 [ISO 3166] for country name
codes), provides all the information necessary to understand XML Version
1.0 and construct computer programs to process it.
I think the references to ISO 639 and ISO 3166 should be replaced with a
reference to the IANA Language Subtag Registry. I note that this is the
only place that these references appear.
2. I recognize that there is difficulty in replacing the reference to
RFC 3066 currently, even though that document is now obsolete, since
3066bis has not be published by the RFC Editor.
3. Section A2 contains a reference [IANA-LANGCODES] which is not
referenced anywhere. Furthermore, this reference is to the now obsolete
and closed Language Tag registry. Changing it to the Language Subtag
registry would be more appropriate.