I'm still struggling with through-the-web ZClass definitions. The test problem I am using as an example is the Actor-Participant object model proposed by Phillip Eby (thanks Phillip!). The people at my academic site each have a folderish PersonClass. Academics typically proceed through undergrad, graduate school, postdoc or alumni, etc. So, beneath the PersonClass I have created an ObjectManager-based PositionClass with properties StartDate and EndDate. I want to use this as a base class for further refinements: DegreeClass, PostDocClass, ProfessorClass, SabbaticalClass, ie., PersonProduct - PersonClass (ObjectManager) PersonClassProperties (FirstName, LastName, Email, URL) - PositionClass (ObjectManager) PositionProperties (StartDate, EndDate) - DegreeClass (PositionClass) DegreeProperties (School, Degree) - AlumniClass (PositionClass) AlumniProperties (CurrentEmployment) ... The idea is for individuals to build up a chronology of positions by adding instances of these PositionClass-derived ZClasses to their respective folders. Here PositionClass is meant to be an abstract class. The user should not be able to create an instance of this class but I cannot figure out how to prevent PositionClass from being an "available object" under PersonClass instances. Any help is much appreciated. Darran.