Re: Namespaces defined

[David Carlisle <davidc@xxxxxxxxx>]

> A namespace is an ASCII text file

No, there need be no physical expression of what consititutes a
namespace.

You could for example use the namespace http://purchasingcenter.com
as the namespace for any elements that you have ever or will ever dream
up. There does not have to be anything at that address that lists the
names, there doesn't have to be anything at the address at all.


The point is if that you have an element x then chances are that someone
else has same, but if you have an element x in namespace
http://purchasingcenter.com then it won't clash with anyone else, and
it's up to you to make sure you don't clash with yourself.
So a namespace parser never actually uses the URI to fetch anything
it is just a unique identifier.

All the prefix rubbish is just a hack to get round the fact that

<{http://purchasingcenter.com,x}> isn't a legal XML name and it is
anyway a pain to type every time.

So the real `abstract' name of your element is the pair
{http://purchasingcenter.com,x}

but when you come to use it in a document you use an (arbitrary)
prefix to stand in for the URL

<p:x xmlns:p="http://purchasingcenter.com"/>

or

<q:x xmlns:q="http://purchasingcenter.com"/>

or indeed

<x xmlns="http://purchasingcenter.com"/>

all mean the same thing, which is the element x from the namespace 
http://purchasingcenter.com

There is (currently at least) no notion of validating that
the specified namespace is supposed to contain an element called x.

You may want to specify that the document validates against a schema or
dtd, but that is a slightly different thing.

David


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