> This would seem to undermine your assertion that XML query languages
> prove that declarative languages work for (XML) hierarchical
> databases. Unless there is something in XQuery that makes navigating
> these secondary relationships as easy as following an XPath, it seems
> to me that XML query languages neither prove nor disprove that
> assertion.
The ability to use a function call within a path expression provides a
reasonably good way of handling secondary relationships. It enables you to
write things such as
customer/customer.orders(.)/order-lines/order-line.product(.)/@code
to follow relationships where the details of the relationship is hidden in
the function implementation.
Another proposal that has been made is to allow user-defined axes. I quite
like that idea, but there seem to be others who hate it.
Michael Kay
