proposal for issue 457

Here is a proposal to accomodate the HTTP use case for UC2 to allow an
implementation to act as a URI resolver using a local cache.
Note that it is not a proposal to actually describe a complete portable
cache (ex: it does not address the variant lists)
The goal here is to give all information used to reconstruct the
information a cache would need.
The calculation of the age and cache validity is up to the application, as
the originator should not be forced to undertand the caching issues of
HTTP/1.1
Exemple:

<htx:env xmlns:htx="http://www.w3.org/2004/02/xop/http">
 <htx:request>
   <htx:request-line name="GET" version="HTTP/1.1">
     /someuri/us.png
   </htx:request-line>
   <htx:header name="Accept">
    image/png,image/jpeg,image/gif
   </htx:header>
   <htx:header name="Accept-Encoding">
    gzip,deflate,compress;q=0.9
   </htx:header>
   <htx:header name="Date">
     Fri, 13 Feb 2004 11:23:28 GMT
   </htx:header>
   [...]
 </htx:request>
 <htx:reply>
  <htx:status-line version="HTTP/1.1" status="200">
   OK
  </htx:status-line>
  <htx:header name="Content-Type">
    image/png
  <htx:header>
  <htx:header name="Date">
   Fri, 13 Feb 2004 11:23:28 GMT
  </htx:header>
    [...]
  </htx:reply>
</htx:env>

It is mainly the complete headers and request/status line for the request
and the reply, as context of the attached binary.

Also, for completeness, the local time when the request is issued (usually
there in the Date: header) and the local time of the same machine when the
reply is received would be a good addition to cope with clock issues,
something like <htx:time>{RFC 1036 time string}</htx:time> in
<htx:request> and <htx:reply>

The only remaining issue regarding time (not fixed) is the possible clock
desynchronization between the SOAP sender and the SOAP recipient.

-- 
Yves Lafon - W3C
"Baroula que barouleras, au tiéu toujou t'entourneras."