Edit comment LC-2023 for Mobile Web Best Practices Working Group

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Comment LC-2023

Comment Shortname:

Commenter: casays <casays@yahoo.com>

Message-id:

Section of the document concerned:

[Free text description]Document as a wholeContent Transformation Guidelines 1.0 Abstract Status of this Document Table of Contents Appendices 1 Introduction (Non-Normative) 1.1 Purpose 1.2 Audience 1.3 Scope 1.4 Summary of Requirements 2 Terminology (Normative) 2.1 Types of Proxy "A transparent proxy is a proxy that does not modify the req... A non-transparent proxy is a proxy that modifies the request... 2.2 Types of Transformation Restructuring content is a process whereby the original layo... Recoding content is a process whereby the layout of the cont... Optimizing content includes removing redundant white space,... 3 Conformance (Normative) 3.1 Classes of Product 3.2 Normative and Informative Parts 3.3 Normative Language for Conformance Requirements 3.4 Content Deployment Conformance 3.5 Transformation Deployment Conformance 4 Behavior of Components (Normative) 4.1 Proxy Forwarding of Request 4.1.1 Applicable HTTP Methods 4.1.2 no-transform directive in Request 4.1.3 Treatment of Requesters that are not Web browsers 4.1.4 Serving Cached Responses 4.1.5 Alteration of HTTP Header Values In this section, the concept of "Web site" is used (rather t... 4.1.5.1 Content Tasting 4.1.5.2 Avoiding "Request Unacceptable" Responses 4.1.5.3 User Selection of Restructured Experience 4.1.5.4 Sequence of Requests 4.1.5.5 Original Headers 4.1.6 Additional HTTP Headers 4.1.6.1 Proxy Treatment of Via Header 4.2 Server Response to Proxy 4.2.1 Use of HTTP 406 Status 4.2.2 Server Origination of Cache-Control: no-transform Including a Cache-Control: no-transform directive can disrup... 4.2.3 Varying Representations 4.2.3.1 Use of Vary HTTP Header 4.2.3.2 Indication of Intended Presentation Media Type of Representation 4.3 Proxy Forwarding of Response to User Agent 4.3.1 Receipt of Cache-Control: no-transform 4.3.2 Receipt of Warning: 214 Transformation Applied 4.3.3 Server Rejection of HTTP Request 4.3.4 Receipt of Vary HTTP Header 4.3.5 Link to "handheld" Representation 4.3.6 Proxy Decision to Transform 4.3.6.1 Alteration of Response 4.3.6.2 HTTPS Link Re-writing 5 Testing (Normative) A References B Example Transformation Interactions (Non-Normative) B.1 Basic Content Tasting by Proxy B.2 Optimization based on Previous Server Interaction B.3 Optimization based on Previous Server Interaction, Server has Changed its Operation B.4 Server Response Indicating that this Representation is Intended for the Target Device B.5 Server Response Indicating that another Representation is Intended for the Target Device C Applicability to Transforming Solutions which are Out of Scope (Non-Normative) D Scope for Future Work (Non-Normative) D.1 POWDER D.2 link HTTP Header D.3 Sources of Device Information D.4 Inter Proxy Communication D.5 Amendment to and Refinement of HTTP E Administrative Arrangements (Non-Normative) F Acknowledgments (Non-Normative)
or

Refinement of the section concerned:

Status:

open proposal pending resolved_yes resolved_no resolved_partial other assigned to Nobody

Type: substantive editorial typo question general comment undefined

Resolution status:

Response drafted Resolution implemented Reply sent to commenter

Response status:

No response from Commenter yet Commenter approved disposition Commenter objected to disposition
Commenter's response (URI):

Comment:

5) Section 4.3.6.1

I miss any discussion or reference in the document about the issue of
character encodings.

Transforming content across different charsets is a mine-field and
affects a number of aspects:
a) Content may rely upon widely different character encodings,
depending on the targetted devices and markets. In particular, the
trio China - Japan - Korea (CJK) continues to rely on a number of
encodings (such as Shift_JIS, BIG5, etc) whose handling is a complex
matter; for instance, there are not necessarily bijective mappings
between these encodings and others, including UTF-8.
b) Documents may have multi-encoding representations. Different
encodings may be associated with external entities through the charset
attribute (see HTML 4.0.1). How transformation proxies deal with such
a situation is left undefined.
c) Similarly, the draft does not explain what happens when a server
associates an attribute accept-charset to a form, and whether proxies
respect or manipulate such information.
d) In i-Mode, and at least in the Softbank environment (Japan),
unreserved character points in the character encoding space are used
to represent pictograms. Any attempt to convert these characters
directly will fail; they should therefore not be transformed, but
preserved, taking into account the fact that the character points thus
referred to differ between Unicode and Shift_JIS, and that DoCoMo and
Softbank do not use the same code points for the same pictograms.

A consequence of all this is that if a proxy does not operate natively
with the character encoding of the content returned by the server, or
is not able to ensure a bijective mapping between this encoding and
other encodings it deals with, recurrent and irrecoverable problems
will creep.
A simple way that could go some way towards alleviating this risk
would be to forbid any transformation if the server announces (either
via the HTTP field Content-type: charset=..., the XML declaration, or
a meta-tag) an encoding different from ASCII or perhaps UTF-8.

Related issues: (space separated ids)

WG Notes: See: http://www.w3.org/2008/09/30-bpwg-minutes.html#item05 Final resolutions: - On character encoding mention this under 4.3.6.1 and respond "Yes partial" to LC-2023 - Mention the out of scope nature of the details of restructuring under 4.3.6 somewhere (cf insertion of headers, footers etc.)

Resolution: Character encoding alterations are out of scope of these guidelines. A note was added in 4.2.9.1 Alteration of Response: http://www.w3.org/TR/2009/WD-ct-guidelines-20091006/Overview.html#sec-alteration-of-response

(Please make sure the resolution is adapted for public consumption)