If posted a proposal at: http://dev.zope.org/Zope3/ActionPlans for manageing complex integrity constraints in a moduler way. Comments are, of course, welcome. Note that this is the next item on my to-do list. Jim -- Jim Fulton mailto:jim at zope.com Python Powered! CTO (540) 361-1714 http://www.python.org Zope Corporation http://www.zope.com http://www.zope.org