RE: Web browsers, HTTP and transcoding

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.

---Rotan.



From: Tom Hume
Sent: Thu 16/10/2008 23:47
To: public-bpwg-ct
Subject: Web browsers, HTTP and transcoding


Folks 


One thing that came up in the last CT group call was the notion that applications other than browsers might make use of HTTP and thereby might be affected by transforming proxies.


As Jo pointed out, the CT document is explicit that its scope is for browsing only. However there are instances where a browser might make HTTP requests which are not for any markup and therefore should not be transcoded; for instance, requests triggered by an XmlHttpRequest implementation as part of a mobile AJAX service.


Section 4.1.3 says that 


The mechanism by which a proxy recognizes the user agent as a Web browser should use evidence from the HTTP request, in particular the User-Agent and Accept headers.


In this case, a user agent which is a web browser may nonetheless be using HTTP GET and POST requests to request content which should not be transcoded. I'm not sure the user agent can be used to disambiguate AJAX HTTP from "regular" browser, and a look through the W3C XMLHttpRequest standard[1] doesn't show any reference to an alternative User Agent being used, and refers (in section 4) to the responses of AJAX calls potentially having a text/html MIME type - so that can't be used either.


Are there considerations around mobile AJAX here - something which may not be prevalent right now, but could be expected to become more so over time? Apologies in advance if I have let out some worms.


Tom


[1] http://www.w3.org/TR/XMLHttpRequest/#send


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