Wow that is really cool. Thanks! (And thank everyone else too!) Your update about doing db updates at same time as filtering is also pertinent.
Yes I will have to study the module to see how to specify rules for subtrees nested inside the Company tag.
My description wasn't so great. My data is basically a Feed of many Company twigs each wrapped in an Entity.
<Feed>
<Entity>
<Company>
<Identity>
<Address>...
</Identity>
<Executives>
<Section>
<Executive>
<Executive>
</Section>
...
</Company>
</Entity>
<Entity>
<Company>
...
and so on.