I would find an abstract ZClass (or Meta ZClass) concept very nice (and useful). I would like to use it, e.g., for a general hieararchical view on relational databases. The view allows browsing (via the tree tag) and selection of one or more items. Most can be implemented independantly of the specific hierarchical relation inside the database. A few parameters and the SQL method are dependant on the database tables. A few others are still more specific, e.g. tree display style and single/multiple selection. Thus, I would prefer the following structure: HV: generic Hierarchical View -- abstract defines the interface and a minimal set of required properties and methods implements most of the functions HV_T1, HV_T2, ...: Hierarchical View specialized for a specific hierarchical relation this (standard) ZClasses define the SQL method and instantiate some parameters of HV i_T1_1, i_T2_2, ...: Instances of HV_T1 more specializations (parameters, presentation methods). Most can be done with the current ZClass architecture: the intermediate ZClasses HV_T1, ... are all derived from ZClass HV. The instances are instances of the intermediate ZClasses. There are 2 exceptions: * HV_T1 cannot specialize properties of HV. They can be specialized in the instances of HV_T1, but it would be nice, if it could be done in the class, if all/most instances share the same value. Workaround: do it in the HV_T1 constructor. * Instances can override property values but not methods. Trying to add a method overriding a default class behaviour results in an "Id already exists" error. Workaround: give the overriding method a different name and let the default method look whether something overriding exists. What do you think about abstract (or Meta) ZClasses? Dieter