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Francois Daoust | 10 Jul 17:34
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Re: Provisional registration of 5 X-Device-* HTTP Header fields for use in content transformation guidelines

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.

Francois.

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
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SM | 10 Jul 18:15

Re: Provisional registration of 5 X-Device-* HTTP Header fields for use in content transformation guidelines

Hi Francois,
At 08:34 10-07-2009, Francois Daoust wrote:
>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.

I'll encourage you to adopt Graham's suggestion of moving to 
"Device-foo" or any other valid name that does not start with 
"X-".  These "X-" headers are generally for private use where the 
interpretation is by private agreement.  There are people outside the 
group that might use that header field for other purposes and they 
are unlikely to look it up in the registry.  If your working group 
already agrees on having one convention, it is better to do away with the "X-".

>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.

You'll have to register that header field as well.

Regards,
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Francois Daoust | 4 Aug 18:31
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Re: Provisional registration of 5 X-Device-* HTTP Header fields for use in content transformation guidelines

Apologies for the late reply, I somehow managed not to see it up until now.

SM wrote:
> Hi Francois,
> At 08:34 10-07-2009, Francois Daoust wrote:
>> 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.
> 
> I'll encourage you to adopt Graham's suggestion of moving to 
> "Device-foo" or any other valid name that does not start with "X-".  
> These "X-" headers are generally for private use where the 
> interpretation is by private agreement.  There are people outside the 
> group that might use that header field for other purposes and they are 
> unlikely to look it up in the registry.  If your working group already 
> agrees on having one convention, it is better to do away with the "X-".
> 

Thanks. I understand the suggestion and the implications of not 
following the suggestion.

At this point, the working group agrees on having one convention among 
the existing ones, which unfortunately all start with "X-". But the
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SM | 12 Aug 08:38

Re: Provisional registration of 5 X-Device-* HTTP Header fields for use in content transformation guidelines

Hi Francois,
At 09:31 04-08-2009, Francois Daoust wrote:
>At this point, the working group agrees on having one convention 
>among the existing ones, which unfortunately all start with "X-". 
>But the working group does not agree to do away with the "X-" not to 
>introduce any kind of new notation. If you're fine with it, the 
>group would thus like to proceed only with the registration of the 
>"X-" versions of the HTTP header fields.

The alternatives are:

   (i) Reject the request as "X-" message header fields names are 
generally not registered in the provisional and permanent Message 
Header Fields registries given that "X-" message header field names 
are reserved for private use.

  (ii) Accept the request for the registration of the five 
"X-Device-*" message header fields in the provisional Message Header 
Field Names registry with a "depreciated" status.

There aren't any "X-" headers in the Permanent Message Header Field 
Names registry.  As the working group does not agree to do away with 
the "X-", there may be a request to register the five "X-Device-*" 
message header fields as permanent Message Header field names.  I 
suggest using the first alternative as the working group does not 
plan to obsolete the five "X-Device-*" HTTP Header fields.

Regards,
-sm
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Francois Daoust | 13 Aug 09:57
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Re: Provisional registration of 5 X-Device-* HTTP Header fields for use in content transformation guidelines

SM wrote:
> Hi Francois,
> At 09:31 04-08-2009, Francois Daoust wrote:
>> At this point, the working group agrees on having one convention among 
>> the existing ones, which unfortunately all start with "X-". But the 
>> working group does not agree to do away with the "X-" not to introduce 
>> any kind of new notation. If you're fine with it, the group would thus 
>> like to proceed only with the registration of the "X-" versions of the 
>> HTTP header fields.
> 
> The alternatives are:
> 
>   (i) Reject the request as "X-" message header fields names are 
> generally not registered in the provisional and permanent Message Header 
> Fields registries given that "X-" message header field names are 
> reserved for private use.
> 
>  (ii) Accept the request for the registration of the five "X-Device-*" 
> message header fields in the provisional Message Header Field Names 
> registry with a "depreciated" status.
> 
> There aren't any "X-" headers in the Permanent Message Header Field 
> Names registry.  As the working group does not agree to do away with the 
> "X-", there may be a request to register the five "X-Device-*" message 
> header fields as permanent Message Header field names.  I suggest using 
> the first alternative as the working group does not plan to obsolete the 
> five "X-Device-*" HTTP Header fields.

I'm not sure I understand why you directly jump to deprecated at this step.
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SM | 14 Aug 08:50

Re: Provisional registration of 5 X-Device-* HTTP Header fields for use in content transformation guidelines

Hi Francois,
At 00:57 13-08-2009, Francois Daoust wrote:
>I'm not sure I understand why you directly jump to deprecated at this step.

A provisional registration is a step towards permanent 
registration.  Omitting the depreciated status would be an 
encouragement to adopt that header field name.  Once that is done, it 
will be argued that the "X-" cannot be dropped.

In future, someone will come up with an argument that there is 
already some "X-" header names in the permanent registry.

>I thought the purpose of the provisional registry was to reserve 
>names while the underlying specification matures along the 
>standard-track. The underlying specification is not definitive, and 
>there will be at least one other Last Call working draft period 
>during which the working group expects to receive external comments 
>both on the choice of names and the usefulness of these HTTP header fields.

Yes.  But if the working group is not agreeing on the change now, it 
is improbable that they will agree to it on another Last Call.

>The use of the "X-" prefix has been extensively discussed both 
>formally within the group and informally with some IETF 
>contributors. The fact that companies use private "X-" header field 
>names on a public level is a pity, but it is unfortunately common 
>practice within mobile networks. We are trying to move away from a 
>situation where there exist 5 different sets of "X-" header field 
>names to a situation where there's only one. Mobile content 
>developers complain about the existence of these different sets that
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Francois Daoust | 14 Aug 12:44
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Re: Provisional registration of 5 X-Device-* HTTP Header fields for use in content transformation guidelines

SM wrote:
> Hi Francois,
> At 00:57 13-08-2009, Francois Daoust wrote:
>> I'm not sure I understand why you directly jump to deprecated at this 
>> step.
> 
> A provisional registration is a step towards permanent registration.  
> Omitting the depreciated status would be an encouragement to adopt that 
> header field name.  Once that is done, it will be argued that the "X-" 
> cannot be dropped.
> 

That makes sense.
In our case, note the "X-" header field names have already been adopted 
in mobile networks, the "X-Device-" form being the most common ones. 
This is why the group argues that the "X-" *already* cannot be dropped.

> In future, someone will come up with an argument that there is already 
> some "X-" header names in the permanent registry.

Perhaps it would be better to issue some recommendation that says "Do 
not use X- prefix at all for new HTTP header fields!". They seem to have 
often been used as synonym to a vendor-specific namespace rather than 
for private experiments. For new HTTP header fields, why not use a 
"real" name and register it provisionally without much ado, perhaps in a 
"private provisional" registry and simply drop this "X-" convention?

For instance, your email client adds an X-Mailer HTTP header field to 
the message. There are other ways such information may be defined in an 
email: Mail-System-Version or Originating-Client for instance. These are
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SM | 14 Aug 22:22

Re: Provisional registration of 5 X-Device-* HTTP Header fields for use in content transformation guidelines

Hi Francois
At 03:44 14-08-2009, Francois Daoust wrote:
>Perhaps it would be better to issue some recommendation that says 
>"Do not use X- prefix at all for new HTTP header fields!". They seem 
>to have often been used as synonym to a vendor-specific namespace 
>rather than for private experiments. For new HTTP header fields, why 
>not use a "real" name and register it provisionally without much 
>ado, perhaps in a "private provisional" registry and simply drop 
>this "X-" convention?

Private would also cover what vendors do internally.  Once they seek 
interoperability with other vendors or use over the Internet, they 
can ask for a registration in the provisional registry.

>For instance, your email client adds an X-Mailer HTTP header field 
>to the message. There are other ways such information may be defined 
>in an email: Mail-System-Version or Originating-Client for instance. 
>These are non-standard HTTP header fields, but they are pretty 
>common. I am not aware of any attempt to standardize one of them. If 
>the info were deemed essential in the end, I guess one of the non 
>"X-" HTTP header fields would probably be used and properly defined 
>and standardized. And yet, whoever introduced them had no real 
>"right" to do that. He should have used an "X-" HTTP header field.

The "X-Mailer:" is a common Internet Message header.  It is 
documented as not part of an Internet Standard and is not in any of 
the message header field names registries.  There are also other 
issues with the message format emitted by my mail server. :-)  It's 
not really about whether we have the "right" to introduce a 
header.  It's more about avoiding conflict by using a common
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