Consider a case, where @processing-role is set as 'resource-only' for a
topicref (say T1). And this topicref has a child topicref (say T2) for which the
@processing-role is set as 'normal'. This may cause issues in processing. T1
shall not be a part of the output as per the description of this attribute. But
T2 shall be there in the output. But it's not clear what would the hierarchy
reflect in the output in navigation/toc, as the parent of T2.

I think this shall be treated as follows:

* T2 shall be eliminated from the output irrespective of the value of
@processing-role for T2. This is because it's parent T1 is set to be excluded
from the output using this attribute.

* So, in general an element shall be excluded from the output, if the
@processing-role is set as 'resource-only' for any of its ancestors. This shall
happen irrespective of the value of @processing-role at the current element.