Re: CTG: non-traditional browsing applications ( LC-2269)

 Dear Eduardo Casais ,

The Mobile Web Best Practices Working Group has reviewed the comments you
sent [1] on the Last Call Working Draft [2] of the Guidelines for Web
Content Transformation Proxies 1.0 published on 6 Oct 2009. Thank you for
having taken the time to review the document and to send us comments!

The Working Group's response to your comment is included below, and has
been implemented in the new version of the document available at:
http://www.w3.org/TR/2010/WD-ct-guidelines-20100211/.

Please review it carefully and let us know by email at
public-bpwg-comments@w3.org if you agree with it or not before 11 March
2010. In case of disagreement, you are requested to provide a specific
solution for or a path to a consensus with the Working Group. If such a
consensus cannot be achieved, you will be given the opportunity to raise a
formal objection which will then be reviewed by the Director during the
transition of this document to the next stage in the W3C Recommendation
Track.

Thanks,

For the Mobile Web Best Practices Working Group,
Dominique Hazaël-Massieux
François Daoust
W3C Staff Contacts

 1. http://www.w3.org/mid/489032.12909.qm@web45015.mail.sp1.yahoo.com
 2. http://www.w3.org/TR/2009/WD-ct-guidelines-20091006/


=====

Your comment on 4.2.9 Proxy Decision to Transform:
> A proposal to amend the CTG with the objective of avoiding deleterious
> interferences
> of transformation proxies with certain non-browsing applications.
> 
> 
> I.	CONTEXT
> 
> Developers are deploying applications that go beyond traditional
> browsing, by taking
> advantage of powerful devices and advanced user agents.
> 
> The cluster of technologies identified as AJAX (AJAX, JSON,
> XMLHttpRequest) has 
> already established itself in the mobile world. Web Services (SOAP,
> WSDL) is another
> one that, while still in its infancy regarding mobile phones, is
> already available
> on laptops with wireless connections.
> 
> The W3C acknowledges the importance of emerging applications based on
> such 
> technologies for the mobile world, notably with respect to AJAX in its
> "Mobile Web 
> Applications Best Practices" (currently under review).
> 
> Section 4.1.3 of the CTG warns about potentially serious problems when
> content
> transformation proxies alter HTTP transactions making up the
> communication flow
> between non-traditional browsing clients and servers. However, the CTG
> do not 
> provide any guidance as to the avoidance of such misoperations.
> 
> In the field, application developers have been facing aggressively
> configured CT
> proxies that interfer with AJAX communications -- on the basis that the
> content
> transmitted over HTTP does not fit into pre-defined categories of
> "mobile browsing",
> is henceforth viewed as "desktop content", and then thoroughly garbled
> by 
> misdirected transformations.
> 
> 
> II.	PROPOSAL
> 
> The following text is included in the normative part of the document:
> 
> "A content transformation proxy MUST handle HTTP requests from a
> terminal, and 
> corresponding responses to them, transparently whenever the HTTP
> transaction
> conveys a payload advertised as one of the following MIME types:
> 
> application/json
> application/xml
> text/xml
> application/soap+xml
> application/soap+fastinfoset
> application/fastsoap
> application/fastinfoset
> 
> These MIME types distinguish traditional browsing transactions from
> AJAX 
> communications and messages in Web Services."
> 
> 
> III.	RATIONALE
> 
> a) Compliance with standards
> 
> The listed MIME types are specified by the IETF or the ITU-T: 
> application/json in RFC4627; 
> application/xml and text/xml in RFC3023; 
> application/soap+xml in RFC3902;
> application/fastinfoset in ITU-T Rec. X.891 | ISO/IEC 24824-1; 
> application/soap+fastinfoset and application/fastsoap in ITU-T Rec.
> X.892 | ISO/IEC 
> 24824-2.
> 
> All are registered at IANA (see
> http://www.iana.org/assignments/media-types).
> 
> b) Application scope
> 
> The listed MIME types are conclusively used for non-traditional
> browsing applications.
> 
> application/json, application/soap+xml, application/soap+fastinfoset
> are exclusively
> associated with AJAX, resp. Web Services applications. 
> 
> The type application/soap+xml is recommended by the W3C for marshalling
> messages 
> between Web Service entities:
> 
> SOAP Version 1.2 Part 1: Messaging Framework (Second Edition)
> W3C Recommendation 27 April 2007
> http://www.w3.org/TR/2007/REC-soap12-part1-20070427
> 
> The W3C further mandates support for this MIME type in:
> 
> SOAP Version 1.2 Part 2: Adjuncts (Second Edition)
> W3C Recommendation 27 April 2007
> http://www.w3.org/TR/2007/REC-soap12-part2-20070427
> 
> MIME types application/xml and text/xml are preferred by the W3C for
> information
> exchange during an AJAX session in its on-going standardization of
> XMLHttpRequest:
> 
> XMLHttpRequest
> W3C Working Draft 20 August 2009
> http://www.w3.org/TR/XMLHttpRequest
> 
> XMLHttpRequest Level 2
> W3C Working Draft 20 August 2009
> http://www.w3.org/TR/XMLHttpRequest2
> 
> These two MIME types are also those that application developers should
> or even must 
> use, according to the documentation of several manufacturers of client
> software.
> 
> c) Overlap with browsing
> 
> The listed MIME types are neither used, nor recommended for traditional
> browsing;
> hence, there is no ambiguity as to the non-applicability of
> transformations on HTTP
> transactions that deal with content of those types.
> 
> d) Generality
> 
> An alternative is to insert a "no-transform" directive in the HTTP
> transactions of
> non-traditional browsing applications. This is however not always
> possible because
> the AJAX or SOAP modules may be compiled packages that cannot be
> configured or 
> modified by the developer (whether in the terminal user agent or on the
> server Web 
> platform), or that are not under the control of the developer
> (terminal: configuration
> only possible manually by users themselves, or only by the operator;
> server: platform
> under the control of the ISP in a shared hosting environment). 
> 
> 
> 
> E.Casais


Working Group Resolution (LC-2269):
We agree and have added the list of data mime types in an appendix
referenced from a bullet point in the list of rules for which proxies
should not transform the response. "application/xml" and "text/xml" were
removed from the list as they may be used to serve XHTML content (although
that is not recommended).

Additionally, section 4.1.3 was completed to point out that more and more
browser based applications involve exchanges of data using XmlHttpRequest
and that alteration of such exchanges is likely to cause misoperation.

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Received on Thursday, 11 February 2010 22:32:05 UTC