> It's really a DOM-style implementation, and the namespace 
> axis just goes 
> up the tree and gathers up the nodes.  So, this breaks when 
> you really on 
> generate-id() as a hack to implement node identity, and also 
> in the case, 
> where you use the parent axis.  In the first case, there's no 
> work-around, 
> while in the second case, there is.
> 

Saxon, as a matter of interest, does exactly the same thing internally, but
when you use the namespace axis explicitly it creates a transient namespace
node with the right parent pointer. This is sufficiently rare that the cost
hardly matters.

Michael Kay