What does "multiple scopes" mean in when talking about MEF (Managed Extensibility Framework) and .NET 4.5?

In What's new in .NET 4.5 microsoft says that MEF will now support "multiple scopes". What does this mean? I can't find documentation on that anyw开发者_如何学运维here.

I belive you question is anwered fully in this blog: http://blogs.msdn.com/b/bclteam/archive/2011/12/19/sharing-with-compositionscopedefinition-in-mef2-alok.aspx