Can XPath do a foreign key lookup across two subtrees of an XML?

Question

Say I have the following XML...

Answer 1

It's not pretty. As with any lookup, you need to use current():

/root/bucket[/root/base/tent[@key = current()/tent/@key]/@color = 'blue' or /root/base/tent[@key = current()/tent/@key]/@color = 'red']