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   Re: [xml-dev] Basic namespace question

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this is an interesting idea? 


On Mon, 17 Jul 2006, Philippe Poulard wrote:

> hi,
> 
> namespace URIs are used to disambiguish names used in elements (and 
> sometimes in attributes) ; the idea is to consider that a name has 2 
> parts, an ID and a local name ; 2 elements that have the same local name 
> are distinct when the ID you choose is not the same than mine ; now what 
> would happenned if unfortunately we have both choosen the same ID ? we 
> would have a clash ; the solution would be :
> 1) to disambiguish again our elements by considering that a name has 3 
> parts (an ID, another ID and a local name) ; now loop again if we choose 
> again the same IDs
> 2) to choose a better ID
> 
> so we must ensure that when you choose an ID, it is not the same than 
> mine ; the idea is to use a "universal ID", an ID that is unique all 
> over the world
> 
> candidates :
> -URIs ("http://foo.com/myNs"; or "urn:isbn:9-780201-770049")
> -GUIDs (they are also expressible with URN : "urn:guid:etc...")
> - la Java ("com.foo.myNs")
> -...
> 
> URIs win
> 
> avoid using "that text document" : even if XML processors won't complain 
> because it's not an URI string, it is not a unique string
> 
> so, the kind of URI you could use could be something like this :
> "http://lle.rochester.edu/myProject/myNs";
> or
> "tag:dgresh@lle.rochester.edu:2006-07-17:myNs"
> or any other, as long as it is unique
> 
> Daniel Gresh wrote:
> > I have a basic question about XML Namespaces, as I just cannot seem to 
> > fully grasp the concept.
> > 
> > I know how to set up a namespace, and I know how they are used in the 
> > document and such; my question is mainly about the URI associated with a 
> > namespace. Let's use this as an example:
> > 
> > |<x xmlns:edi='http://ecommerce.org/schema'>
> >  <!-- the 'price' element's namespace is http://ecommerce.org/schema -->
> >  <edi:price units='Euro'>32.18</edi:price>
> > </x>||
> > 
> > Now I'm not too sure how to phrase this question, but here goes: do I 
> > have to associate a URI with a namespace? In the above example, what 
> > would be the case if there was no xmlns declaration and the ns "edi" was 
> > used? I suppose what I am asking is: what is the benefit of declaring an 
> > xmlns in the manner  xmlns:prefix='URI'? Is information from that URI 
> > being used in the XML document somehow? It's all very confusing to me.
> > 
> > Also, let's say I have a simple text document located somewhere on my 
> > hard drive, like C:\document.txt. If I wanted to define a namespace for 
> > that document, such as  xmlns:doc='that text document', how exactly 
> > would I do so? Is it even needed?
> > 
> > Thanks in advance,
> > Dan
> > |
> > 
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> 





 

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