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Re: XPath data model and the XML Declaration

From: Bjoern Hoehrmann <bjoern@---------.-->
To: NULL
Date: 12/2/2004 4:25:00 PM

* Richard Tobin wrote in comp.text.xml:
>>The XML declaration does not contain information that
>>would make sense to be available in the data model.
>
>But this is an exaggeration.  The encoding is a useful hint when
>serializing the data model, and the XML version number affects what
>assumptions you can make about the data (e.g. whether it might have
>C0 control characters in it).

The problem is however that the value of the encoding pseudo-attribute
might not be the actual character encoding of the document, for example
if the document is delivered via HTTP the acutal encoding might be 
specified in the HTTP header which would then override the value in the
XML declaration (if any). So it would make more sense to use other means
to get that information, for example using DOM Level 3 Core methods. 

Regarding C0 control characters, I do not think these may appear in the
XPath 1.0 data model which is only defined for XML 1.0 (they are not
allowed to appear in expressions either, strings are restricted to chars
as defined in XML 1.0 which excludes C0 controls)... and if they are in
the data model, you can infer that the XML version is 1.1 so this is of
limited use, too.

Other uses would be possible too, for example, if you want to write an
XSLT document that discovers meta-data from XML documents like

  XML Declaration: yes
  Encoding Declaration: ISO-8859-1
  Standalone: no

  Elements:

    1 <html>
    1 <head>
    1 <body>
   32 <div>
  ...

or whatever, so maybe I should rephrase to, the value such functionality
would add is not considered worth the additional complication and such
functionality might contribute to making false assumptions such as that
the encoding in the XML declaration is the actual document encoding.
-- 
Björn Höhrmann · mailto:bjoern@h... · http://bjoern.hoehrmann.de
Weinh. Str. 22 · Telefon: +49(0)621/4309674 · http://www.bjoernsworld.de
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