On 2012/11/17 9:56, Philippe Verdy wrote:
True. HTML5 makes its own reinterpretation of the IETF's MIME standard,
definining it own protocol (which means that it is no longer fully
compatible with MIME and its IANA datatabase, because the mapping of the
value of a charset="" pseudo-attribute is not directly to the IETF MIME
standard, but to a newer range of W3C standards).
There was a clear desire from the W3C to deprecate the use of the MIME
standard and its IANA database in HTML, to simplify the implementations
There is no need to deprecate the use of MIME in order to simplify
implementations. No MIME-compatible implementation is required to accept
and understand all "charset"s defined in the IANA registry. There are
numerous Mime types that restrict the number of possible character
encodings to a small set, or only require implementation of very few of
them (XML would be a typical example).
(also to avoid the many incompatibilities that have occured in the past
with MIME charsets between the implementations).
That's the main motivation. One browser started to accept data in a form
that it shouldn't have accepted. Sloppy content producers started to
rely on this. Because the browser in question was the dominant browser,
other browsers had to try and re-engineer and follow that browser, or
just be ignored. The Encoding Spec is an attempt, hopefully successful,
to limit these incompatibilities to those that exist today, and not let
them increase further.
Note also that the W3C
does not automatically endorses the Unicode and ISO/IEC 10646 standards as
well (there's a delay before accepting newer releases of TUS and ISO/IEC
10646, and the W3C frequently adds now several restrictions).
Can you give examples? As far as I'm aware, the W3C has always tried to
make sure that e.g. new characters encoded in Unicode can be used as
soon as possible. There are some cases where this has been missed in the
past (e.g. XML naming rules), but where corrective action has been taken.
Regards, Martin.
2012/11/17 Doug Ewell<[email protected]>
If he is targeting HTML5, then none of this matters, because HTML5 says
that ISO 8859-1 is really Windows-1252.
For example, there is no C1 control called NL in Windows-1252. There is
only 0x85, which maps to U+2026 HORIZONTAL ELLIPSIS.
--
Doug Ewell | Thornton, Colorado, USA
http://www.ewellic.org | @DougEwell
From: Philippe Verdy
Sent: Friday, November 16, 2012 17:35
To: Whistler, Ken
Cc: Buck Golemon ; [email protected]
Subject: Re: latin1 decoder implementation
In fact not really, because Unicode DOES assign more precise semantics to
a few of these controls, notably for those given whitespace and newline
properties (notably TAB, LF, CR in C0 controls and NL in C1 controls, with
a few additional constraints for the CR+LF sequence) as they are part of
almost all plain text protocols ; NUL also has a specific behavior which is
so common that it cannot be mapped to anything else than a terminator or
separator of plain text sequences.
So even if the ISO/IEC 8859 standard does not specify a charecter mapping
in C0 and C1 controls, the registered MIME types are doing so (but nothing
is well defined for the C0 and C1 controls except NUL, TAB, CR, LF, NL, for
MIME usages purpose).
And then yes, the ISO/IEC 8859 standard is different (more restrictive)
from the MIME charsets defined by the IETF in some RFC's (and registered in
the IANA registry), simply because the ISO/IEC standard (encoded charset)
was developed to be compatible with various encoding schemes, some of them
defined by ISO, some others defined by other standard European or
East-Asian bodies (including 7-bit schemes, using escape sequences, or
shift in/out controls).
By itself, the ISO/IEC 8859 is not a complete encoding scheme, it is just
defining several encoded character sets, independantly of the encoding
schme used to store or transport it (it is not even sufficient to represent
any plain-text content).
On the opposite, The MIME "charsets" named "ISO_8859-*" registered by the
IETF in the IANA registry are "concrete" encoding schemes, based on the
ISO/IEC 8859 standard, and suitable for representing a plain-text content,
because the MIME charsets are also adding a text presentation protocol.
In practice, almost nobody today uses the ISO/IEC 8859 standard alone :
there's always an additional concrete protocol added on top of it (which
generally makes use of the C0 and C1 controls, but not necessarily, and not
always the same way). So plain-text documents never use the ISO/IEC 8859
standard, but the MIME charsets (plus a few specific or proprietary
charsets that have not been registered in the IANA registry as they are
bound to a non-open protocol).
