> node() matches the root node, for example in the following 
> XPath expression:
> 
>      ancestor::node()

But ancestor::node() is not a valid match pattern.

In XSLT 1.0, the only pattern that matches the root node is "/".

In XSLT 2.0, you can use patterns of the form document-node()[predicate].

Michael Kay
http://www.saxonica.com/