t agree with Pat's claim that the upper level of the merged
&gt;ontology is 'fixed' or less subject to modification than the lower levels.
&gt;In fact, the upper level has undergone more revisions than any of the lower
&gt;level ontologies that were grafted on to it.

Yes, you are right, and I chose my words poorly: sorry. I didn't mean 
to accuse you of being overly rigid in not altering the upper levels. 
What I meant was that you see the process as one of fitting lower 
categories into supercategories: t