Restricted Namespaces for XML

Ronald Bourret rbourret at
Thu Feb 4 12:21:35 GMT 1999

Don Park wrote:

> Such a spec might dictate that all namespace declarations be at the root
> element (XML fragments are problematic but...).  This restriction has the
> side effect of not allowing duplicate prefixes.

The major benefit of this proposal is that it reduces the number of checks 
for xmlns attributes. This savings is minimal in small documents or 
documents with few attributes, but it would be interesting to know how much 
xmlns attribute processing costs in a large, attribute-intensive document.

I think readability is a wash, as you can't do anything more with this than 
you can with the current proposal and you lose the ability to have multiple 
default namespaces, which are useful in documents that have long sections 
alternating between two or more namespaces.

I think the biggest problem is, as James Clark noted elsewhere, 
complication of fragmentation.  Since I believe fragments to be a big part 
of the future, I don't like anything that will make them harder.

That said, if anybody had some real numbers about what xmlns attribute 
processing costs in the worst case and this turned out to be significant, 
it might be useful to have a PI that tells the namespace processor whether 
it needs to look beyond the root element.

-- Ron Bourret

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