LC-2052: Content types and DOCTYPEs

Comment:

3) Section 4.3.6

The third bullet under "examples of heuristics" is to be split into two
points:

"the Content-Type of the response are known to be specific to the device
or class of device. At a minimum, the following MIME types intended for
mobile Web browsers MUST represent mobile-optimized content:

Browsing XHTML-related
application/vnd.wap.xhtml+xml
application/xhtml+xml
Browsing WML-related
text/vnd.wap.wml
application/vnd.wap.wmlc
text/vnd.wap.wml+xml
text/vnd.wap.wmlscript
application/vnd.wap.wmlscriptc
image/vnd.wap.wbmp
application/vnd.wap.wbxml
Browsing and downloading
application/vnd.wap.multipart.mixed
application/vnd.wap.multipart.related
application/vnd.wap.multipart.alternative
application/vnd.wap.multipart.form-data

In addition, the following MIME types of the form */x-up-* SHOULD be
considered as representing mobile-optimized content, at a minimum:

Legacy Openwave
image/x-up-wpng
image/x-up-bmp

The range of MIME types is intended to cover typical mobile browsing
applications.

Transformations specified by the relevant standards are allowed (WAP-236
WAE specifications 19.12.2001, WAP-192 WBXML specifications 25.7.2001,
WAP-191 WML specifications 19.2.2000 and predecessors, WAP-193 WMLScript
specifications 25.10.2000).

In accordance with Internet standards and practices, a proxy SHOULD
determine whether a content is mobile-optimized FIRST by examining the
HTTP header field content-type, before inspecting the XML declaration
and its associated DOCTYPE."

Rationale: Inspection of the HTTP field Content-type is an usual mode of
operation amongst transcoders. It is also simpler and safer than
applying heuristics on DOCTYPE, because inspecting the content of a body
requires one to deal with character encoding issues (see RFC3023, XML
1.1 sections 4.3.3 and E), or parsing multipart-structured content;
these are unnecessary when handling HTTP fields. Finally, specifying a
minimum set of required MIME types to take into account helps ensure
that proxies will exhibit a standard behaviour, and that non-textual
content types for which there is no DOCTYPE (notably mobile-specific
image formats) are properly dealt with. A normative document cannot
leave full freedom to implementors to select whichever subset of content
types are to be considered mobile-optimized or not.

4) Section 4.3.6

The second part of the bullet split as described in (b) is to contain
the following:

"other aspects of the response such as the DOCTYPE are known to be
specific to the device or class of device.

At a minimum, the following DOCTYPEs MUST be considered as
mobile-specific:

XHTML mobile profile
-//OMA//DTD XHTML Mobile 1.2//EN
-//WAPFORUM//DTD XHTML Mobile 1.1//EN
-//WAPFORUM//DTD XHTML Mobile 1.0//EN
XHTML basic
-//W3C//DTD XHTML Basic 1.1//EN
-//W3C//DTD XHTML Basic 1.0//EN
-//OPENWAVE//DTD XHTML 1.0//EN
-//OPENWAVE//DTD XHTML Mobile 1.0//EN
XHTML i-Mode
-//i-mode group (ja)//DTD XHTML i-XHTML (Locale/Ver.=ja/1.0) 1.0//EN
-//i-mode group (ja)//DTD XHTML i-XHTML (Locale/Ver.=ja/1.1) 1.0//EN
-//i-mode group (ja)//DTD XHTML i-XHTML (Locale/Ver.=ja/2.0) 1.0//EN
-//i-mode group (ja)//DTD XHTML i-XHTML (Locale/Ver.=ja/2.1) 1.0//EN
-//i-mode group (ja)//DTD XHTML i-XHTML (Locale/Ver.=ja/2.2) 1.0//EN
[list completed in
http://lists.w3.org/Archives/Public/public-bpwg-comments/2008JulSep/0150
.html with:
-//i-mode group (ja)//DTD XHTML i-XHTML (Locale/Ver.=ja/2.3)
1.0//EN]
Compact HTML
-//W3C//DTD Compact HTML 1.0 Draft//EN
-//BBSW//DTD Compact HTML 2.0//EN

The following DOCTYPEs MUST be considered as mobile-specific.
Transformations explicitly provided for by the relevant standards are
allowed (WAP-192 WBXML specifications 25.7.2001, WAP-236 WAE
specifications 19.12.2001, WAP-191 WML specifications 19.2.2000 and
predecessors, WAP-193 WMLScript specifications 25.10.2000).

WML
-//WAPFORUM//DTD WML 1.0//EN
-//WAPFORUM//DTD WML 1.1//EN
-//WAPFORUM//DTD WML 1.2//EN
-//WAPFORUM//DTD WML 1.3//EN
-//WAPFORUM//DTD WML 2.0//EN
-//PHONE.COM//DTD WML 1.1//EN
-//OPENWAVE.COM//DTD WML 1.3//EN

The range of MIME types is intended to cover typical mobile browsing
applications."

Rationale: A normative document cannot leave full freedom to
implementors to select whichever subset of DOCTYPEs are considered
mobile-optimized or not. This helps ensure that transformation proxies
exhibit a standard behaviour.


Proposed Response:

See LC-1998 for the application/xhtml+xml content type and content types
in general.  We decided a while back to not put examples of content
types in the CT Guidelines.  There were too many of them and there
seemed to be a lot of ambiguity.  Point taken on dealing with character
encoding issues with the DOCTYPE which are not a problem with the
Content-Type header.  It is possible we need to revisit the content type
heuristic topic.

DOCTYPEs:  These seem like valid DOCTYPEs to put in the guidelines.
However, section 4.3.6 was never meant to be an exhaustive list of all
heuristics; just some examples.  We should probably have some discussion
on whether we want to try to be more exhaustive.


Sean