W3C home > Mailing lists > Public > public-bpwg-ct@w3.org > October 2008

RE: Web browsers, HTTP and transcoding

From: Robert Finean <Rob.Finean@openwave.com>
Date: Fri, 17 Oct 2008 11:55:30 +0100
Message-ID: <7F652B9B6A93184AB38BBCF677E7287A05057466@bfs-exch-prd1.myopwv.com>
To: "Rotan Hanrahan" <rotan.hanrahan@mobileaware.com>, "Tom Hume" <Tom.Hume@futureplatforms.com>
Cc: "public-bpwg-ct" <public-bpwg-ct@w3.org>
<< 

If you know that CTs won't manipulate an XML payload that doesn't look
like a page, then you can use XML MIME types too.

>> 

That's a safe bet; see section 4.3.6 of the CT-Guidelines.

 

<< 

keep track of the MIME type of the previous request (in the same
session?)

>> 

Unfortunately this assumes a handset isn't multi-tasking (eg RSS reader
requests in the middle of a browser session, with identical User-Agent)
so this isn't easy in practise.

Thanks,

Rob

--
OPENWAVE

Dr Robert Finean
Open Internet Products Manager

________________________________

From: public-bpwg-ct-request@w3.org
[mailto:public-bpwg-ct-request@w3.org] On Behalf Of Rotan Hanrahan
Sent: Fri 17 October 2008 01:01
To: Tom Hume
Cc: public-bpwg-ct
Subject: RE: Web browsers, HTTP and transcoding

 

No. The implications don't go both ways. I was pointing out that a
mobile application using Ajax that wants to be immune from interference
from an intermediary CT will need to use a payload format that is
unlikely to be of interest to the CT. A text/plain payload should do the
trick, if the app developer is assuming the CT only looks at the MIME
type and won't take an interest in text. If you know that CTs won't
manipulate an XML payload that doesn't look like a page, then you can
use XML MIME types too. If CTs assume all XML MIME types are adaptable,
then you're in trouble with that format.

 

However, from the CT perspective you have the problem of trying to
distinguish between a normal browser request and a request via XHR,
where it is likely that the implementer of the Web application didn't
take any action to avoid interference from CT proxies.

 

In this case, you might try to be more clever and keep track of the MIME
type of the previous request (in the same session?) of the the device
and look for unusual shifts between markup types. You could sniff the
beginning of the page to see if it really is a page, or just a fragment,
or some crazy invented XML language. There's no easy answer when you're
a CT and trying to deal with XHR apps that didn't anticipate your
presence.

 

It would certainly be nicer if XHR flagged itself in the UA, but I think
we're too late.

 

---Rotan

 

 

 

________________________________

From: Tom Hume
Sent: Fri 17/10/2008 00:02
To: Rotan Hanrahan
Cc: public-bpwg-ct
Subject: Re: Web browsers, HTTP and transcoding

Does this imply that transcoding proxies shouldn't transcode items of
content with MIME types that is "text/xml, application/xml or ends in
+xml (ignoring any parameters)" (the ones referred to in the XHR
standard)? 

 

On 16 Oct 2008, at 23:51, Rotan Hanrahan wrote:





In these scenarios, mobile Ajax should stick to raw text, XML or JSON as
a payload format. If it is communicating with fragments of HTML and
you've already adapted (or otherwise "enhanced") the page in which the
Ajax is operating, the chances of that fragment of HTML being of any use
any more (adapted or not) are significantly diminished already.

 

Good point about the UA though. I must double-check.

 

--

Future Platforms Ltd

e: Tom.Hume@futureplatforms.com

t: +44 (0) 1273 819038

m: +44 (0) 7971 781422

company: http://www.futureplatforms.com/

personal: tomhume.org
Received on Friday, 17 October 2008 10:56:37 GMT

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