[gdome]Accessing Namespace Declarations

["T.J. Mather" <tjmather tjmather com>]

According to the DOM Level 2 Core spec, section 1.1.8:

"As far as the DOM is concerned, special attributes used for declaring XML 
namespaces are still exposed and can be manipulated just like any other 
attribute."

So this leads me to believe that getAttributes, getAttribute, etc should 
return XML namespace declarations as well as normal attributes.  The 
current behavior doesn't return namespace declarations.

In libxml2's xmlNode structure, XML namespace declarations are stored
in "nsDef", and all other attributes are stored in "properties".  The
current implementation only accesses "properties", hence the current 
behavior that doesn't return namespace attributes.
See:
http://xmlsoft.org/html/libxml-tree.html#XMLNODE

So we could use "nsDef" to access the xml namespace declaration 
attributes, as follows:

* namespace declarations will be wrapped in the GdomeAttr interface
  when exposed through attribute methods.  Note that this is 
  different from the XPath module where the namespace
  declarations exposed through XPath are wrapped in the 
  GdomeXPathNamespace interface.
* getAttribute* and hasAttribute* methods will continue
  to access "properties" for attributes, but will also look in "nsDef" 
  for namespace attributes.
* setAttribute* and removeAttribute* methods will work as before, except
  will die with NO_MODIFICATION_ALLOWED_ERR if attribute is wrapper
  to nsDef.  that is, pre-existing namespace declarations can not
  be removed, modified or used to set attributes.  this is consistent with
  the fact that XPathNamespace nodes are read-only and cannot be
  placed in the document hierarchy.
* an additional member will be added to the _Gdome_xml_Attr structure:
	GdomeBoolean namespaceDecl;
  If set to 1, then *n contains a xmlNs pointer, otherwise
  contains a xmlAttr pointer.

Thoughts?  This seems to be a tricky problem, so I like to hear back from 
some of the experts on this list.  I can take care of implementing it, as 
I do need this to work soon, like in the next day or so.

In case any one is curious, I need this for XML::Canonical to work 
properly with XML::GDOME.

Thanks,
TJ