RE: namespace markup

I don't quite know if I should be flattered. All I did was
reading aloud from "Namespaces in XML 1.0 (Second
Edition)" [1].

XML namespace name rules *are* confusing:

  "The empty string, though it is a legal URI
reference, cannot be used as a namespace name."

And a few lines further:

  "The attribute's [used in the namespace declaration]
normalized value MUST be either a URI reference - the
namespace name identifying the namespace - or an empty
string."

A bit more reading aloud, this time from one of the editors
[2]:

  There is no such thing as the "blank namespace"
or the "empty namespace" or the "unqualified
namespace."

The point is that the empty string does not identify any XML
namespace. Rather, it can be used as the attribute value in
an XML namespace declaration to undeclare an XML namespace
prefix (since Namespaces 1.1) or the default namespace. See
also [3].

The <uri> element was introduced to mark up -- among
other things -- XML namespace names [4]. I suppose one can
argue that it is better than, say, <span
class="xmlNamespace">...</span>. It is a
quagmire though, if you want to do anything with it besides
rendering. Naming and versioning a vocabulary is inherently
difficult.

By the way, what is the appropriate way to mark up a QName?

Kind regards
Peter Ring

[1] http://www.w3.org/
TR/REC-xml-names
[2] http://www.tbray.org/ongoing/When/200x/2003/08/0
8/NamespaceOrNot
[3] http://www.rpbourret.com/xml/NamespacesFAQ.htm#decl_7
[4] http://lists.oasis-open.org/archives/docbook/20
0306/msg00051.html

> -----Original Message-----
> From: Dave Pawson [mailto:davepdpawson.co.uk]
> Sent: 8. marts 2007 18:01
> To: Peter Ring
> Cc: docbooklists.oasis-open.org
> Subject: Re: [docbook] namespace markup
> 
> 
> Peter Ring wrote:
> > An XML namespace is not an URI; rather it is is 
> *identified* by an URI reference.
> 
> Oh dear.
> (I hate people who are 'right'
> .... especially when I didn't think of it.
> 
> 
> 
> 
>   To be more precise, a subset of URI references with
semantics that 
> differ from URI references in general.
> > 
> > The empty string is an URI reference, but the
empty string 
> cannot be used as an XML namespace name.
> We'll let that pass (default ns?)
> 
>   Relative URI references are deprecated as XML
namespace names.
> 
> +1
> 
>   XML namespace names are compared by string equality,
i.e. 
> not the way 
> URI references are resolved. [1]
> 
> No, but as 'strings' they are uri's?
> > 
> > In short: an XML namespace name looks a lot like
an URI, 
> 
> and an XML namespace declaration look a lot like
assigning a 
> value to an 
> attribute.
> 
> But you cannot really infer much about the semantics of
XML 
> namespaces 
> from that. An XML namespace name is not a type of URI.
> 
> Tell you what Peter.
> I'll ask the stupid questions.
> You come back with the 'right' answers, to guide us,
> and the db comittee can think about it for a while.
> 
> Agreed?
> 
> 
> regards
> 
> -- 
> Dave Pawson
> XSLT XSL-FO FAQ.
> http://www.dpawson.co.uk

> 

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