l10n.lang.value.rfc.compliant — Make value of lang attribute RFC compliant?
If non-zero, ensure that the values for all
lang attributes in HTML output are RFC
by taking any underscore characters in any
lang values found in source documents, and
replacing them with hyphen characters in output HTML files. For
zh_CN in a source document becomes
zh-CN in the HTML output form that source.
This parameter does not cause any case change in
lang values, because RFC 1766
explicitly states that all "language tags" (as it calls them) "are
to be treated as case insensitive".
[RFC1766] defines and explains the language codes that must be used in HTML documents.
Briefly, language codes consist of a primary code and a possibly empty series of subcodes:language-code = primary-code ( "-" subcode )*
And in RFC 1766, Tags for the Identification of Languages, the EBNF for "language tag" is given as:Language-Tag = Primary-tag *( "-" Subtag ) Primary-tag = 1*8ALPHA Subtag = 1*8ALPHA