Re: How namespaces are unique???

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On Thursday 30 May 2002 05:05, Mailer Mailer wrote:
> both had namespace definition like this:
>
> xmlns:calp="http://url1.com/meta/calp"
>
> xmlns:calp-"http://url2.com/bit/calbit"
>
>
> Can anyone explain me how namespace is resolving the
> conflict, when the these prefix names are same???

As I'm sure many people will tell you, the prefix **doesn't matter at all**.  
It is what comes after the prefix that counts.  In fact, if you do 
xmlns="...", you can have a namespace without a prefix at all.

The following elements are all completely equivilant:

<foo xmlns="bar"/>
<prefix:foo xmlns:prefix="bar"/>
<xx:foo xmlns:xx="bar"/>

And the following elements are all totally different:

<prefix:foo xmlns:prefix="bar"/>
<prefix:foo xmlns:prefix="zap"/>
<foo xmlns="zoip"/>
<foo xmlns="xyz"/>

The prefix is merely a shorthand way of telling the XML processor which URI is 
associated with the element.  The processor uses whatever xmlns declaration 
for a given prefix is in scope.  So even if two elements with the same 
prefixes exist in a single document, they can have different namespaces and 
therefore be totally different elements:

<document>
  <element xmlns:prefix="bar">
    <prefix:foo/>
  </element>
  <element xmlns:prefix="zap">
    <!-- this <foo> is different from the first -->
    <prefix:foo/>
  </element>
</document>

The only thing that matters is the URI that is the value of the xmlns 
declaration.  If the two URIs are not *exactly* the same, then any elements 
using the prefixes associated with the different URIs will be in different 
namespaces.

The fact that most URIs take the form of "http://foo.com/..." does not mean 
that the server at foo.com is contacted at all.  Think of the URI as merely a 
string of characters that has nothing to do with any actual internet 
protocol.  Even if www.foo.com and www2.foo.com resolve to the same server, 
"http://www.foo.com/namespace" and "http://www2.foo.com/namespace" will be 
different namespaces.

BTW, have you ever heard of google?  I find it hard to believe that this 
question has not already been answered thousands of times :)

- -- 
Peter Davis
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