The issue number refers to the XLS-sheet found in this email:
http://lists.oasis-open.org/archives/xacml/200909/msg00013.html
The commenter says that the ancestor attributes in the XML case are not
needed since the hierarchy information is already there in the XML document.
The attributes are intended to be used with the xpath match functions to
grant access to sections of an XML document. It is probably true that
these attributes are redundant since it is probably possible to achieve
the same effect using xpath expressions which match sections of the XML
document.
However, I have not done a careful analysis of whether this is really
true, or which approach is more efficient. Also, it would be good to
keep the attributes for compatibility with XACML 2.0.
So I propose that we make no change.
Best regards,
Erik