Re: [Ietf-message-headers] Provisional registration of 5 X-Device-* HTTP Header fields for use in content transformation guidelines

Francois Daoust <> Fri, 10 July 2009 15:34 UTC

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Date: Fri, 10 Jul 2009 17:34:36 +0200
From: Francois Daoust <>
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Subject: Re: [Ietf-message-headers] Provisional registration of 5 X-Device-* HTTP Header fields for use in content transformation guidelines
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Hi Graham,

The situation the Mobile Web Best Practices working group is trying to 
address is one where different vendors used different HTTP header field 
conventions (all starting with 'X-') for the same use in their proxies, 
requiring content providers to support the different names when they 
wanted to do things properly. What the working group would like to do is 
to shrink the list of existing conventions to one and only one 
convention, but would prefer not to introduce any new convention (be it 
the last one) for that to happen. The 'X-Device-foo' format is the most 
commonly used format in the list based on the group's experience, and 
thus the chosen one.

That said, I have nothing against provisional registration of both 
forms. I add the topic to the working group's agenda for discussion. I 
suppose that, in any case, if we register the 'X-Device-User-Agent' 
header field, the 'Device-User-Agent' header field de facto would become 
"unavailable", not to trigger any confusion.


Graham Klyne wrote:
> Concerning the use of X- headers.
> A similar situation existed with the X-Archived-At header field [1].  
> When that proposal went to standard/recommendation, the 'X-' was dropped 
> for the permanent registration [2], but the 'X-' version was retained in 
> the provisional registry [3], marked as 'Deprecated'.
> Assuming that you intend your specification to proceed to REC, I would 
> suggest a similar approach here.  In which case, you may wish to 
> consider provisional registration of both forms.
> (The provisional header registry was intended, in part, to address 
> unsatisfactory aspects of the 'X-' naming convention illustrated by 
> cases like this.)
> [1]
> [2]
> [3]
> #g
> -- 
> Francois Daoust wrote:
>> Hi,
>> Please find below the registration template for 5 HTTP header fields 
>> the W3C Mobile Web Best Practices Working Group would like to 
>> provisionally register for use in the "Guidelines for Web Content 
>> Transformation Proxies" specification it is currently working on.
>> Note on the presence of the "X-" prefix: names were chosen on the 
>> basis that there are a already existing and deployed convention. Since 
>> there is no easy way to transition out of a situation where an "X-" 
>> prefix has been used for other purpose than a purely experimental one, 
>> the W3C Mobile Web Best Practices Working Group acknowledges that 
>> these HTTP header field names are already in use and requests that the 
>> "X-" prefix be (exceptionally) kept.
>> -----
>> Header field names:
>> X-Device-User-Agent (request header)
>> X-Device-Accept (request header)
>> X-Device-Accept-Charset (request header)
>> X-Device-Accept-Encoding (request header)
>> X-Device-Accept-Language (request header)
>> Applicable protocol:
>> http
>> Status:
>> provisional
>> Author/Change controller:
>> W3C Mobile Web Best Practices Working Group
>> Specification document(s):
>> (Editor's Draft)
>> (Working Draft)
>> See section " Original Header Fields" in the documents.
>> -----
>> I will submit the above template to the designated IANA e-mail address 
>> beginning of August, unless some explicit disagreement is made on this 
>> list.
>> Regards,
>> On behalf of the W3C Mobile Web Best Practices Working Group,
>> Francois Daoust,
>> W3C Staff Contact for the group.
>> _______________________________________________
>> Ietf-message-headers mailing list