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Duplicated guidelines for Web Content Transformation Proxies

From: Francois Daoust <fd@w3.org>
Date: Tue, 08 Dec 2009 17:53:22 +0100
Message-ID: <4B1E8482.7040602@w3.org>
To: Mobile Web Best Practices Working Group WG <public-bpwg@w3.org>
Hi,

While re-reading the spec in preparation for the F2F with a "let's think 
about tests" hat, I realized that a few normative guidelines appear 
duplicated. The statements already reference the other section where 
they are repeated, but I think using normative terms more than once 
should be avoided as it's source of confusion for implementers.


Duplicate guideline in 4.1.5 and 4.1.5.5
-----
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


Duplicate guideline in 4.1.6 and 4.1.6.1
-----
In 4.1.6 [3], the normative bullet point:
[[ proxies must include a Via HTTP header field (see 4.1.6.1 Proxy 
Treatment of Via Header Field). ]]

... refers to 4.1.6.1 [4] where the beginning of the sentence is 
basically the same thing:
[[ Proxies must (in accordance with RFC 2616) include a Via HTTP header 
field indicating their presence ]]


Normative statement in an example
-----
In 4.1.5.5 [2], the "For example" statement contains a normative 
statement. It is correct but it seems awkward to find a normative 
statement in the middle of an example:
[[ For example, if the User-Agent  header field has been altered, an 
X-Device-User-Agent header field must be added with the value of the 
received User-Agent header field. ]]

It can be turned into an informative-only example, as the normative 
statement is contained in the guideline that precedes it.


I do not think that removing duplicates (be them normative) constitutes 
a substantive change, as the conformance statements remain the same.

Francois.


[1] 
http://www.w3.org/TR/2009/WD-ct-guidelines-20091006/#sec-altering-header-values
[2] 
http://www.w3.org/TR/2009/WD-ct-guidelines-20091006/#sec-original-headers
[3] 
http://www.w3.org/TR/2009/WD-ct-guidelines-20091006/#sec-additional-headers
[4] http://www.w3.org/TR/2009/WD-ct-guidelines-20091006/#sec-via-headers
Received on Tuesday, 8 December 2009 16:54:00 UTC

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