[Pear][QuickForm][DB_DataObject] Architecture

Hello anyone! I am, probably like lotsa more readers of this list, experimenting with Pear::QuickForm a lot. What I actualy would like to do is a relatively smart usage of QuickForm, DB_DataObjects and Smarty as my template engine (could be any other tho).. To get an overview of what I will talk/ask about I would love you to check out the following UML-like-class-diagram: http://progress.risse.org/pear/uml_class1.gif I would like to know what you guys think about this approach or if you have any additions to it? Furthermore my instance of the derived "CustomQuickFormClass" doesnt work as xpected. After adding my custom code to the constructor I added parent::HTML_QuickForm(..params..), so usually everything with the derived Object should be okay, but unfortunately QuickForm doesnt do all the rule_checks I added in the constructor. Why? I read in the src, that I could register a custom "callback"-function, but I dont really know if this would help, because I dont know what the "callback"-function is xpected to be and do. Any help would be heavily appreciated. Yours, Matthias