[xsl] How to select an attribute on the current node or its anchestor

[Philipp Kursawe <phil.kursawe@xxxxxxxxx>]

Hello,

given the following xml:

<node data="foo">
B  <text id="1" data="bar"/>
B  <text id="2"/>
</node>

I would like to know the XPath expression to select @data which
results in "bar" for @id=1 and "foo" for @id=2.

The general idea is to search for the attribute in the anchestor if
the current node does not contain the attribute all the way up to the
root node.

Thanks for your help!

Phil