Language-tag vs. language-range

[mnot@…]

​http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-22#section-3.1.3.1 says:

HTTP uses language tags within the Accept-Language and Content-Language fields.

language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>

Section 3.1.3.1 defines a language tag by reference to RFC5646 section 2.1.

Per ​http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-22#section-5.3.5 the Accept-Language header, however, uses a language-range not a language-tag:

Accept-Language = 1#( language-range [ weight ] ) language-range =

<language-range, defined in [RFC4647], Section 2.1>

Note the different reference, and following that reference we find the explicit statement that:

A basic language range differs from the language tags defined in [RFC4646] only in that there is no requirement that it be "well- formed" or be validated against the IANA Language Subtag Registry.

And of course RFC5646 obsoletes RFC4646 but doesn't change the relevant ABNF.

So the Accept-Language tag does not use the language-tag production, it uses the looser language-range definition).

The text in section 3.1.3.1 is confusing because it can be misread to imply that Accept-Language uses the language-tag production.

Suggest:

HTTP uses language tags within the Accept-Language and Content-Language fields. The Accept-Language field uses the looser language-range production defined in Section 5.2.5, whereas the Content-Language field uses the stricter language-tag production defined below.

language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>

[julian.reschke@…]

From [2293]:

tune language introducing Accept-Language (see #456)

[fielding@…]

From [2323]:

improve the description of language tags to be closer to what is defined by RFC5646; updates [2293] which addresses #456