xml-dev - Re: SAX2: Namespace Processing and NSUtils helper class

[David Brownell <david-b@pacbell.net>]

Tim Bray wrote:
> 
> At 10:32 AM 1/5/00 -0800, David Brownell wrote:
> >Namespace URIs clearly have three kinds of values, not that
> >it's specified in the namespace spec very clearly (and I suspect DOM L2
> >may need tweaking to get this right):
> >
> >       - Undeclared (null?)
> >       - Declared as no-value (empty string, "")
> >       - Some URI (the case folk focus on).
> 
> No.  The second case is explicitly ruled out by the namespace spec.  Check
> sections 2 and 5.2 of the namespace spec.

I think you've gotten confused by the multiple iterations on this
topic.  Likely not the only person!

My original statement was about an error case, an undeclared prefix.
The followup was about a non-error case, the default namespace, and
specifically what 'xmlns=""' does.  That response addressed both issues.

To be clearer, the cases correspond to these XML documents:

	- undeclared prefix (error for namespace, but legal XML)
		<prefix:EXAMPLE />

	- default namespace (per namespace spec, sections 2, 5.2)
		<root xmlns="http://foo">
			<EXAMPLE xmlns:prefix="" />
		</root>
	  and similarly
		<EXAMPLE />

	- Some URI
		<prefix:EXAMPLE xmlns:prefix="http://foo" />

That is, there's a distinction between "declaration needed and missing"
and "default namespace".

Since the XML standard doesn't directly incorporate the namespaces
spec (and make the first case be a fatal error), there needs to be
some way to deal with that first case, and some way that it'll be
exposed through APIs.  Perhaps you have a suggestion about another
way to expose it?

- Dave

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