ISSUE-257: Clarification of section 4.1.2

Is the CT-proxy aware?

Clarification of section 4.1.2

Guidelines for Web Content Transformation Proxies
Raised by:
François Daoust
Opened on:
As discussed a bit between Jo and I as part of ISSUE-255:

...the intent of the section 4.1.2 in latest draft is unclear:

Since we dropped all kinds of possibilities for the CT-proxy to advertise, in the request, the fact that it intends to transform the response, having the CT-proxy decide, when it receives a request, whether it's likely to transform the response ends up being a moot point because there's no consequence as far as the guidelines are concerned.

The section should therefore be about "Proxy Forwarding of Request".
That's mostly the case anyway, save the first part that lists heuristics to determine whether it intends to offer transformation services.

1. rename section 4.1.2 to "Proxy Forwarding of Request"

2. drop first bullet list in 4.1.2 about intention "to offer transformation services"

3. amend first bullet in 4.4 on previous interaction with the server with the note on the consistency of user experience that was in 4.1.2.

4. update the sentence "If, as a result of carrying out this analysis the proxy remains unaware of the server's preferences and capabilities it SHOULD" to something like "If, taking into account the result of previous interaction with the server, the proxy remains unaware of the server's preferences and capabilities it SHOULD"

The last point is motivated by the fact that the other previously listed heuristics should not impact the decision of the Proxy to send the unaltered request and then the altered one. Note that CT-proxies may still use whatever heuristics they may want to use to determine if they are "aware" or not.

Francois (realizes he's trying to start a discussion on "awareness", wonders if he should change his nickname to JCVD ;-))
Related Actions Items:
No related actions
Related emails:
  1. [minutes] BPWG F2F in Sophia, day 1 (from on 2008-06-17)
  2. Content Transformation Guidelines - preparation for the F2F (from on 2008-06-13)
  3. [minutes] CT Call Tuesday 10 June 2008 (from on 2008-06-10)
  4. ISSUE-257 (Is the CT-proxy aware?): Clarification of section 4.1.2 [Content Transformation Guidelines] (from on 2008-06-10)

Related notes:

See for proposed edits to 4.1.2

Dominique Hazaël-Massieux, 16 Jun 2008, 09:58:46

RESOLUTION: Adopt Jo's wording for 4.1.2 of the CT document (pending some editorial "tweaking") and close ISSUE-257:
<jo> Proxies should not intervene in methods other than GET, POST, HEAD and PUT.
If there is a no-transform directive present in the request the proxy should not modify the request headers.
The proxy should not modify request headers unless:
a) the user would be prohibited from accessing content as a result of a
406 or bogus 200 response;
b) the user has specifically requested a restructured desktop experience;
c) the request is part of a session of some sort and either it is
technically infeasible not to adjust the request because of earlier
interaction, or because doing so preserves a consistency of user experience.
Rejection of a request by a server is taken to mean both a HTTP 406 Status as well as HTTP 200 Status, with content indicating that the request cannot be handled - e.g. "Your browser is not supported"

Dominique Hazaël-Massieux, 16 Jun 2008, 10:14:56

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Jo Rabin <>, Daniel Appelquist <>, Chairs, Dominique Hazaël-Massieux <>, François Daoust <>, Staff Contacts
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