Re: Duplicated guidelines for Web Content Transformation Proxie

> In 4.1.5 [1], the normative statement:
> [[ It must be possible for the server to reconstruct the 
> original User Agent originated header fields by copying
> directly from the corresponding X-Device header field
> values (see 4.1.5.5 Original Header Fields). ]]
>
>... refers to 4.1.5.5 [2] where it is more properly defined:
> [[ When forwarding an HTTP request with altered HTTP
> header fields, in addition to complying with the rules of 
> normal HTTP operation, proxies must include in the
> request copies of the unaltered header field values 
> in the form "X-Device-"<original header name>. ]]
>
> From a normative point of view, the first statement does
> not add anything. I understand it is there for emphasis, 
> but could perhaps be turned into an informative
> statement that delegates to 4.1.5.5

There is a subtle, but important point in the first statement
(which was added at my insistence, by the way): it 
ensures that one does not have to interpret or parse the
values in the X-Device fields in any new way -- one can 
just copy the field values and thus recuperate directly the
original header fields. 

The second statement strictly states that the X-Device 
fields must include copies of the original values, but by 
itself does not prevent the addition of extra content, or
bracketing the original values within something else (for
instance, placing the original field values within some XML
markup tags, that would have to be parsed out when
recuperating the original string).

This is why there is no redundancy in this case.

As for 4.1.5.5, the sentence "For example, if the 
User-Agent header field has been altered, an 
X-Device-User-Agent header field must be added..."
could be changed so that the must is no longer
emphasized in the way denoting a normative statement.


E.Casais

Received on Tuesday, 8 December 2009 18:07:06 UTC