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I am getting ready to build an Organizational Chart 'product' within Zope.

Where does this information reside now? That would dictate what approach you take. I once did something similar for a company where the data resided in an ldap db, but it was far too slow to recursively query in real time so I had to dump it to a relation db every night which I could query quickly.

For the primary client that I am working with, the bulk of the information that we are going to put in here does not really exist in any location yet. I'm deciding to make this a product because I have some plans to use this in a couple of sites which don't exist anywhere other than my mind right now <g>

Anyway, once a person logs on and you know their unique identifier, you should be able to query the datasource to see where they sit in the hierarchy when trying to edit another user. Just a thought.

Given that I plan on keeping this stuff in ZODB instead of an external RDBMS, I'm not clear on how you find an object when going 'down' a tree.