If you are a Microsoft.NET developer, you can take advantage from the full source from codeplex at:
http://www.codeplex.com/MEF
Read more on MEF at:
http://code.msdn.microsoft.com/mef
the basic idea being extensible is being able to dynamically compose stuffs, without being able to recompile the entire application source.
As an example if you have seen or heard of the pouplar game War of the worlds (WoW), the model are being extended by many-2 contributors and the ability of the game application to handle these .
It may be required to restart the application in order to index or utilize the new models, Depending on the implementation it is highly possible to differentiate changes that requires restart and the changes which can be acomodated/invalidated dynamically.
In all MEF unleashes the Framework with capacity in order to build highly Extensible applications which can be maintained by. These can be leveraged in order to build highly customizable applications.
