[news.eclipse.technology.equinox] Overriding IExtensionRegistry / IExten

[Eric Rizzo <eclipse-news@xxxxxxxxxxxx>]

Are there any articles, examples, or other help for overriding the 
default behavior of IExtensionRegistry, IExtensionPoint, and IExtension?
The reason I (think) I want to do this is because we have a requirement 
to prevent reading extension contributions from certain plugins, even if 
they are installed. In other words, if certain conditions about a plugin 
are satisfied, we need to prevent any extensions from that plugin from 
being contributed at runtime.

Any pointers?

Thanks in advance,
Eric