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   RE: [xml-dev] Effective XML

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> -----Original Message-----
> From: Bullard, Claude L (Len) [mailto:clbullar@ingr.com]
> Sent: 02 January 2002 22:19
> To: Michael Brennan; 'Leigh Dodds'; xml-dev
> Subject: RE: [xml-dev] Effective XML


> Is it better to use a namespace or to copy an element type 
> or attribute type definition into a new schema?  IOW, by 
> what criteria should one choose between a namespace reference 
> and a clone?
> Maintenance is obvious but not a problem.  I would suggest 
> that it is cheaper to copy if the overlap among several 
> schema is small (just a few common element and attribute 
> types).

I'd agree with this. 

I'd guess that the most common example at the moment of use 
by reference is to include XHTML elements where one needs to 
include markup text (e.g. product descriptions) within another 

The overlaps might not be just be defined in terms of numbers of 
elements/attributes, but also whether the 'concept' (for want of 
a better term) that is being marked up is a natural subset of 
the existing schema. For the XHTML example, this is paragraphs of 

Another way to consider this and a potential advantage of this 
kind of modularity is that these document fragments in another 
namespace can be handed off to other components in a 
pipeline. E.g. an HTML renderer. Reuse of existing markup definitions 
allows reuse of these components, or where these don't exist, 
provide a means of specifying a standard input for a new component.
Copying references increases the size of the interface to such 
components or requires adapters.




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