Re: knowlegde distilled from the UML 2.0 infrastructure

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From: Brian Henderson-Sellers (
Date: Tue 22 Apr 2003 - 23:18:49 BST

> Bt 'ancestor' you mean Gen/Spec stuff?
> Has anyone ever tried to understand and maintain C++ classes with more than 4 levels of inheritance? It's almost impossible!  With 18 levels we are in a new realm. 
> Chances are that the wrong things are being inherited etc.

We did some research years ago to evaluate the claim then that inheritance
hierarchies should be no more than 7 deep. We analyzed available commercial
libraries in various languages and found that none were deeper. The results
are published in Australian Computer Journal, 29(3), 81-94, 1997
> Should we not ban inheritance (Im serious)? I consider it harmful when used for the wrong things.

While not banning inheritance, I certainly downplay it and suggest it is a
"last resort" or at least introduced into the design later rather than sooner


Brian H-S


Professor Brian Henderson-Sellers
Director, Centre for Object Technology Applications and Research
    and Professor of Information Systems
Faculty of Information Technology
University of Technology, Sydney 
P.O. Box 123                        Tel: +61 (0)2 9514 1687
Broadway                            Fax: +61 (0)2 9514 4535
NSW 2007                            email:

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