25d39a0e_der_com___Revit_3D__March_2008__In_Revit_2009___
[Revit 2008 Feature] External material libraries [For more information] Materials, Rendering Appearance Library, Transferring Project Standards [In Revit 2009...] 
Material definitions are stored as part of the project file. Render appearances are stored in a local, read-only library. If you make any changes to render appearances for materials, the changes are stored as part of the project. To share changes to render appearances with team members, use File menuTransfer Project Standards.
BIMBuilder.com / Revit 3D: March 2008
In Revit 2009...