Quoting Dimitre Novatchev <dnovatchev@xxxxxxxxx>:

> > > Nevertheless, I'm reasonably comfortable with it.
> >
> > I think the place where it breaks down most spectacularly is when it
> > is combined with the apparent desire to model SQL NUL values as () 
> > using a list, even an empty one, as a value does not really combine 
> > with the non nested list model, which means that these "NUL" values 
> > vanish at interesting times and lead to strange anomalies in  
> > accumulation functions like sum() and the loss of the useful
> lisp-like
> > non-empty-node-set = true  coercion that was in Xpath 1 but only
> works
> > in Xpath 2 "most of the time".
> > 
> > David
> 
> Also as Jeni pointed out the weird case of sequences changing their
> cardinality when mapped by a function that may return the null
> sequence...

That's very dangerous.  It means that if one were doing several different 
mapping operations from the same sequence the results could might be 
incorrectly aligned.

I can't fathom how anyone could consider that as acceptable behavior.


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