[W3C BPWG] HTTP header fields X-* and normal ones / question

I am writing on behalf of the W3C Mobile Web Best Practice Working Group

1) Context.

The W3C BPWG is currently elaborating guidelines for content transformation
proxies, i.e. proxies that modify HTTP requests sent by terminals and
returned by application servers; the paramount case is transforming WWW
intended for desktops in a format suitable for mobile devices, notably

2) Issue.

Some content transformation proxies modify the HTTP request header, and
the original information in extra backup header fields. These header fields
concern the client capabilities. The backup fields are prefixed with
-- X-Device-User-Agent, X-Device-Accept, X-Device-Accept-Charset, 
X-Device-Accept-Language, X-Device-Accept-Encoding.

The W3C BPWG is looking into formalizing these backup fields and registering
them as proper HTTP header fields in the IANA registry according to RFC3864.
This implies that they be renamed in view of eliminating the X- prefix (for
instance, Device-Accept instead of X-Device-Accept), since it appears that
HTTP header fields of the pattern X-... are not allowed to be registered (a
probable consequence of RFC822).

Because deployed transformation proxies rely upon the backup fields with the
X-Device- prefix, and all deployed proxies cannot be updated to use new
names in a "big bang" switch-over, the W3C BPWG is potentially facing a
migration period where both the old, X-Device- fields, and the newer, e.g.
Device- fields, may have to coexist.

3) Questions to the IETF.

3.a: What is the IETF procedure, policy, standard, or best practice
the promotion of X- header fields to normal, registered (provisionally or 
permanently) header fields?

3.b: What is the policy, standard or best practice of the IETF regarding the
simultaneous deployment and utilization of two sets of header fields, which 
have the same semantics, one comprising fields of the pattern X- and the
fields of a normal pattern?

3.c: What is the procedure, policy, standard or best practice of the IETF
regarding the deprecation and discontinuance of HTTP header fields?

Many thanks in advance for your answers.

Eduardo Casais
areppim AG
Bern, Switzerland

Received on Wednesday, 21 January 2009 14:44:58 UTC