At least from what I can see, there is no way to know which fact a particular column originates from. It would be very useful if this could be added. I am currently writing a transform that will attempt to generate MS_Description extended properties from the exported xml. This way there will be a description on each column and table in the database describing where it originated from in the conceptual model. In addition, some code generation utilites will read those descriptions and expose them as C# xml comments.