[Typo3-dev] Extend extensions

[typo3 at isfates.com]

Hi,

I am developping a base extension class (kind of abstract class) and some other 
classes which should extend this base extension.

The problem I have is that the base class has to be loaded before the extending 
classes. Is there a *recommended* way to make sure that one class is loaded 
before another in Typo3? (I tried to set the dependency flag on the extending 
extensions, so that Typo3 knows that the base extension has to be loaded, but 
it won't work)

Best regards

Georges