>>Hmm, I get the feeling that our hunches of abstract versus concrete are not entirely equal. You may well be right, but I also would like to hear what others have to say about it.
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>Maybe I'm just to fond of my init code...

I think you have learned and thought about the subject a lot more than I have done in the past. Without your input I'd not have had the hunches I now have. But it's my hope that others too show their insights or perception. The outcome may well be used to upgrade NewClass.app.

My current pov is that the choice between creating an 'abstract class' and a 'concrete class' must be redefined to: 'incomplete class' versus 'complete class'. 'Incomplete' implying that the developer is free to directly use it on a form, but still will have to add code to certain methods and set certain properties to valid values. Those methods and properties ideally need to be documented.

In a reply to Thomas you used the word dynamically. Indeed, this concept of an incomplete class can be seen as a case of an abstract class that is dynamically upgraded to a complete class that can then indeed be instantiated to a concrete object.