When debugging skinscript, especially tricky dependencies between what gets computed when during state changes, do the following: 1: Run zope in debug mode (-D) 2: Put an external method called print_ in the root of your ZODB, with the code: def print_(s): print s 3: In your SkinScript, if you want to know when a trigger is called, or when a set of attributes get computed, use this kind of thing: WITH QUERY foo(id=some_id) COMPUTE thing=RESULT, bar=baz, _printout_foo=self.print_('query foo called, id=%s' % some_id) OTHERWISE LET thing=_.None, bar='no bar', _printout_foo=self.print_('query foo called, otherwise clause') WHEN OBJECT CHANGED CALL print_('CHANGED start'), Catalog .uncatalog_object(_.string.join(self.getPhysicalPath(),'/')), print_('CHANGED middle'), Catalog .catalog_object(self, _.string.join(self.getPhysicalPath(),'/')), print_('CHANGED end') 4: Read the debug printout, and work out that you're computing attributes for cataloging before changing the attributes they depend on. 5: Amend code and skinscript, test, document code, sleep. -- Steve Alexander Software Engineer Cat-Box limited http://www.cat-box.net