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Re: Is the P-word? (Was: TAG Decision on Rescinding the request to the HTML WG to develop a polyglot guide)

From: David Sheets <kosmo.zb@gmail.com>
Date: Tue, 22 Jan 2013 21:18:00 -0800
Message-ID: <CAAWM5Ty8crxEnXBV9GGRtQhtgdkS1_G6UHSRXrGEbP=LfyDkkQ@mail.gmail.com>
To: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
Cc: Henri Sivonen <hsivonen@iki.fi>, Daniel Glazman <daniel@glazman.org>, Sam Ruby <rubys@intertwingly.net>, Noah Mendelsohn <nrm@arcanedomain.com>, "www-tag@w3.org List" <www-tag@w3.org>, "public-html@w3.org" <public-html@w3.org>
On Tue, Jan 22, 2013 at 4:15 PM, Leif Halvard Silli
<xn--mlform-iua@xn--mlform-iua.no> wrote:
> Henri Sivonen, Tue, 22 Jan 2013 10:55:53 +0200:
>> Please don't support outputting encodings other than UTF-8.
> Polyglot.
>> Either way, XML processors are required to support UTF-8 and UTF-16.
>> Support for other encodings is optional. In other words, other
>> encodings are not guaranteed to work.
> Only Polyglot - and neither HTML5 or XML - limits the encoding to UTF-8.
>>>   - xhtml 1 or 1.1
>>>   - html5, xml serialization, not poyglot
>>>   - html5, xml serialization, polyglot
>>> I can make the difference between the first and the two last ones based
>>> on the doctype and friends. I am unable to make any difference between
>>> the two last ones.
>> Don't support polyglot. Problem solved.
> Don't support non-polyglot. Problem solved. (Don't change your message
> because of the label.)

What is the reason that
<http://dev.w3.org/html5/html-xhtml-author-guide/#content-type> says

The HTTP Content-Type: header has no extra rules or restrictions,
whereas polyglot markup does not use the http-equiv="Content-Type"
declaration on the meta element.


As I read HTML5 and prior specs, @http-equiv='Content-Type' doesn't
have much meaning other than to (maybe) declare the charset encoding
for the doc. The TAG says

Metadata received in an encapsulating container, such as the metadata
within the header fields of a message that describe the data enclosed
within that message, is authoritative in defining the nature of the
data received.

See also <http://www.w3.org/2001/tag/doc/mime-respect#embedded>.

This suggests to me that putting something like

<meta http-equiv="Content-Type" content="application/xhtml+xml" />

is a potential way to indicate to text/html consumers that this
representation is also parseable by an XML parser and interpretable by
an XHTML renderer.

Is this ill-advised for some reason? Is there a pitfall here of which
I am ignorant?

It would be nice to embed useful metadata indicating that the present
representation is intended to have identical semantics under different
media types' interpretations. This would give multi-modal consumers a
means to leverage both HTML and XML processing on the document if so


Received on Wednesday, 23 January 2013 05:18:54 UTC

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