multiple encoding specs (Re: IE5.0 does not conform to RFC2376)

John Cowan cowan at
Fri Apr 9 18:05:21 BST 1999

Rick Jelliffe wrote:

> Given that an XML processor may transcode the document without knowing
> the meanings of the elements (i.e., that the meta tag means something),
> the XML encoding has to have priority over the HTML meta tag value. And
> given that a proxies can transcode text/* files without knowing what
> kind of text it is (i.e., that it is XML, and so has a label), the MIME
> header has to have priority over the XML header PI. I think that is the
> logical order: generic operations must be allowed.

All extremely sound.

> However, it is all spoiled if there are systems which corrupt the
> labels: for example by rewriting the charset parameter incorrectly. It
> is far better to send the XML file without a charset parameter than to
> send it with a wrong one.

But there's the snag: in text/xml documents, a missing charset parameter
does not mean "Charset unspecified"; it means "Charset specified
as US-ASCII".  There is no way to fail to specify a charset in
text/* documents, and rightly so, because text without a charset
is uninterpretable.

In SGML terms, omitting the charset in text/* documents is a mere
minimization, whereas in application/* documents it is a true #IMPLIED.

John Cowan		cowan at
	You tollerday donsk?  N.  You tolkatiff scowegian?  Nn.
	You spigotty anglease?  Nnn.  You phonio saxo?  Nnnn.
		Clear all so!  'Tis a Jute.... (Finnegans Wake 16.5)

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