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Re: SVG12: image/svg+xml gzip requirements

From: Bjoern Hoehrmann <derhoermi@gmx.net>
Date: Fri, 10 Dec 2004 06:33:19 +0100
To: Chris Lilley <chris@w3.org>
Cc: www-svg@w3.org, ietf-types@iana.org
Message-ID: <41bc267b.582282093@smtp.bjoern.hoehrmann.de>

* Chris Lilley wrote:
>BH> Use of the +xml convention implies that such metadata needs to be
>BH> overridden
>
>No, it does not. An xml encoding declaration is sender provided
>metadata. However, in the case where a charset parameter is allowed, and
>where it can be different, and thus where one has to win over the other,
>metadata is indeed being overridden. I agree with you that silent
>recovery here is not inthe user interest and a warning should be shown.

You either missed that the mail you responded to did not discuss the
charset parameter at all, or you are trying to suggest that there is
a character encoding that is based on gzip. Such a character encoing
would of course by easy to construct,

  In order to encode a XML document using the gzip-xml character
  encoding, the XML document is first serialized using a second
  character encoding such that the resulting octet sequence meets
  the requirements of the XML 1.0 Recommendation. The new octet
  sequence is then compressed using the gzip method as defined in
  RFC 1952.

  In order to decode a gzip-xml encoded XML document, the octet
  stream that represents the XML document is first uncompressed
  using the method defined in RFC 1952. The decoder determines
  then the character encoding of the resulting octet sequence as
  defined in the XML 1.0 Recommendation and decodes the sequence
  according to this character encoding with the exception that
  the resulting character sequence must be constructed such that
  XML processors that would processes the character sequence
  would only read EncName nonterminals that match "gzip-xml" in
  order to circumvent the the requirment in the XML 1.0 Rec that
    
    ... it is a fatal error for an entity including an encoding
    declaration to be presented to the XML processor in an
    encoding other than that named in the declaration ...

  Implementations may implement other algorithms than those
  described above as long as those alternate algorithms yield
  in the same processing result.

If you imply this gzip-xml character encoding then there is indeed
no metadata that is overriden (unless there happend to be higher-
level protocol information that would require XML processors to
determine a character encoding that is different from "gzip-xml").
If that is your point, I should probably request that support for
this gzip-xml character encoding is required for SVG Viewers...
-- 
Björn Höhrmann · mailto:bjoern@hoehrmann.de · http://bjoern.hoehrmann.de
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Received on Friday, 10 December 2004 05:33:39 GMT

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