Stefan H. Holek writes:

I have this ZCallable product (from the PTK, I think). I do however not manage to derive a ZClass from ZCallable. The error is something like "Too many datafull base classes".

Is ZCallable not intended to work like that (the source hints to some ExtensionClass business) or am I missing something? The ExtensionClass docu tells that among all classes involved in a class, at most one extension class may define data extensions.

Apparently, ZCallable is such an extension class that defines a data extension (or inherits from a class that does). And obviously, your class derives from another such class. If you are lucky, ZCallable is a superset of the other class and you can drop the other. Unfortunately, I do not know with ExtensionClass'es define extensions. Dieter