Re: [xml-dev] Quiz: how many namespaces are in scope?

[Michael Kay <mike@saxonica.com>]

> That's an odd definition of "namespace node," to my mind.  You're
> asserting that each element node has three namespace "nodes" associated
> with it?

You might think it odd, but that is exactly what the XDM data model (and 
the XPath 1.0 data model before it) defines.

And it has some considerable advantages, notably that when you copy any 
subtree rooted at an element node, the copy automatically retains the 
full namespace context.

However, it has to be said that the model has confused a great many 
people, because (a) it is somewhat distantly related to the lexical view 
of XML that they see on the screen in front of them, and (b) they find 
it hard to envisage how it might be efficiently implemented. These two 
factors have led to a great deal of resistance to the model.

I think that if XQuery Update had bought in fully to the namespace node 
model, the namespace-related semantics of XQuery Update would probably 
be a lot cleaner.

Michael Kay
Saxonica