[Zope] Data aggregation within a tree

[Brad Knotwell]

Hello all--

My application has two custom objects types (one of them is
folderish).  I'm trying to add a view to the folderish object that'll
aggregate statistics information on the lower-levels of the tree.

Specifically, I'd like a flavor for how to do the following:

    traverse a tree w/o rendering it
    test an object's type
    if an object is a specific type:
       update counters appropriately based on the internal state of
       the object

    render the results

Since I only want to traverse the tree (not render it), am I correct 
in presuming dtml-tree isn't my friend in this case and I'll need to
work in straight Python instead?

Thanks in advance.

--Brad