>>Rick, If you are talking about OO then the right person to read is Alan Kay, after all he coined the term, so go tell him that inheritance is not part of it but interfaces are.
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>Deep class hierarchies are evil.
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>Inheritance is fine, just used in a minimal way. Even the various patterns revolve around inheritance, but in a limited way. Maintainable code spreads horizontally (composition) rather than vertically (inheritance)...
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>+++ Rick ---

I know about the issues deep class hierarchies, there are also issues with composition and there are even people that are not even sold on the whole design patterns paradigm, and then you have interfaces which can also be overused (and many times they are used to overcome issues that should not exist in an OO language, in my opinion). So, now that we established that all solutions have the potential of causing troubles, lets go back to the original assertion:

> Inheritance (which is what you get with VFP subclassing) is pretty much frowned on. There are exceptions, of course. Interfaces, Composition, Aggregation are much better OO practices.

The four pillars that I mentioned are 1.Abstraction 2.Encapsulation 3.Modularity 4.Hierarchy, those are basic principles of OO. Interfaces, Composition, Aggregation are NOT much better OO practices, they are techniques or mechanisms used to solve or overcome issues with a more pure OO approach, for example maintainability, as you said.