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From Bernd Fondermann <bf_...@brainlounge.de>
Subject Re: [Vysper] XML Namespaces [WAS: Re: Moving new nbxml in trunk]
Date Sun, 09 May 2010 19:52:21 GMT
Niklas Gustavsson wrote:
> On Sun, May 9, 2010 at 8:23 PM, Bernd Fondermann <bf_jak@brainlounge.de> wrote:
>> What I wanted to achieve with the initial implementation, is that
>> namespaces get propagated automatically within the scope. That's also my
>> notion of how XML default namespaces are scoped and what the patch is
>> solving.
> 
> This would go against every XML API I know of. For example, what would
> be the namespace of an element if I use it outside of its original
> parent?
> 
> Also, the namespace URI of an element is just as important as its
> local name, so, I would rather this be explicit when we create an
> element, than having to backtrace in the code whatever namespace the
> parent might have.
> 
>> So my resultion would be:
>> + propagating default namespaces to inner elements is implicit. (means:
>> possible reverting revision 941337, which is an strange revision number
>> anyway ;-)
> 
> Again, I would be strongly against this. It would make the Vysper XML
> API work completely different from all the XML APIs (Java or not) I've
> ever used. And I believe that's true for many other developers. The
> XML APIs that I'm familiar with that behaves like this are DOM (Java
> and Javascript), XOM, JDOM, DOM4J, .Net XmlDocument and SAX (yes, I'm
> somewhat of an XML geek :-).

ok, let's talk more on code, so I can be sure to understand correctly.

I'm argueing alongside the last example in
  http://www.w3.org/TR/REC-xml-names/ , chapter 6.2

This example is especially appropriate, as it includes beer:

<?xml version='1.0'?>
<Beers>
  <!-- the default namespace inside tables is that of HTML -->
  <table xmlns='http://www.w3.org/1999/xhtml'>
   <th><td>Name</td><td>Origin</td><td>Description</td></th>
   <tr>
     <!-- no default namespace inside table cells -->
     <td><brandName xmlns="">Huntsman</brandName></td>
     <td><origin xmlns="">Bath, UK</origin></td>
     <td>
       <details xmlns=""><class>Bitter</class><hop>Fuggles</hop>
         <pro>Wonderful hop, light alcohol, good summer beer</pro>
         <con>Fragile; excessive variance pub to pub</con>
         </details>
        </td>
      </tr>
    </table>
  </Beers>

Now, I'd like to have an API like this:
builder.add("table", "http://www.w3.org/1999/xhtml").
    add("th").
    add("tf").
    addText("Name") ...

and *not*
builder.add("table", "http://www.w3.org/1999/xhtml").
    add("th", "http://www.w3.org/1999/xhtml").
    add("tf", "http://www.w3.org/1999/xhtml").
    addText("Name") ...

while you'd like it the other way round, right?

Reason for my position: This is straihtforward. You don't redefine java
variables when a new scope opens. You'd just redefine them to
shadow/override the outer scoped variable.
The inner XML elements are not arbitrary. Within a table, you'd expect
td, tr etc. to occur. No need to redefine the namespace.
However, if non-table elements occur, the namespace gets reset explicitly.

And I don't think you can get rid of looking up outer namespaces in any
serious implementation. In the second example, where every add() has an
explicit namespace declaration, one would
* either repeatedly render the declared xmlns on every element, no
tracking of outer ns needed
* or, not repeat rendering the declared xmlns, (like *all* XML examples
I've seen so far) which can only be achieved by keeping track of what
the current namespace is.

I don't think XML like this:
  <table xmlns='http://www.w3.org/1999/xhtml'>
   <th xmlns='http://www.w3.org/1999/xhtml'>
<td xmlns='http://www.w3.org/1999/xhtml'>Name
...
would be very compatible with XMPP clients. And would put much more
bytes on the wire than neccessary.

Am I missing something?

  Bernd




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