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ACTION-818: Write some text for CT Appendix B.3

From: Francois Daoust <fd@w3.org>
Date: Wed, 23 Jul 2008 15:47:32 +0200
Message-ID: <48873674.9060706@w3.org>
To: public-bpwg-ct <public-bpwg-ct@w3.org>

Hi,

This is my contribution for Appendix B.3.

It's a bit long, but it's also the longest scenario we have, I guess.
Jo, feel free to adjust the wording as necessary for this to be 
considered as real English ;-)

Francois.


-----
Steps 1 to 8 are an example of a series of events that may lead a proxy 
to choose to optimize its interactions with a Web Site by sending 
requests with altered headers directly.
Steps 9 to 12 detail how a server may advise the proxy that the 
optimization is not valid for all resources, and the behavior of the 
proxy on receipt of such information.
Steps 13 to 16 explain the behavior of the proxy for subsequent requests.

1. The user requests resource P on a Web Site S.
2. The proxy intercepts the request, and requests resource P with 
original headers.
3. The server does not vary its representations for resource P, 
determines that the available representation does not meet e.g. the 
original Accept header, and returns an HTTP Status 406 Not Acceptable 
response.
4. The proxy receives the unacceptable response, and re-requests 
resource P with altered headers.
5. The server returns the representation of resource P compatible with 
the altered headers.
6. The proxy parses the response, may apply transformation if needed and 
possible, and forwards the response to the user.
7. The user browses the response and clicks on a link to resource Q.
8. The proxy intercepts the request, determines (by unspecified means) 
that resource Q is on the same Web Site S as resource P, remembers the 
unacceptable response it received for the request on resource P, and 
requests resource Q directly with altered headers.

9. The server has available different representations of resource Q 
based on the User-Agent and Accept headers, and returns the 
representation of resource Q adapted to the altered headers served with 
an HTTP Vary header set to "User-Agent, Accept".
10. The proxy detects the HTTP Vary header, and re-requests resource Q 
with original headers.
11. The server returns the representation of resource Q adapted to the 
original headers.
12. The proxy parses the response, may apply transformation if needed 
and possible, and forwards the response to the user.

13. The user browses the response and clicks on another link to resource Z.
14. The proxy intercepts the request, determines (by unspecified means) 
that resource Z is on the same Web Site S as resources P and Q, 
remembers that the server varies its representations for resource Q, and 
requests resource Z with original headers.
15. The server has available different representations of resource Z 
based on the User-Agent and Accept headers, and returns the 
representation of resource Z adapted to the altered headers served with 
an HTTP Vary header set to "User-Agent, Accept".
16. The proxy parses the response, may apply transformation if needed 
and possible, and forwards the response to the user.
-----
Received on Wednesday, 23 July 2008 13:48:09 GMT

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