The proprietary Autodesk MapGuide file format that contains the spatial data (such as roads, cities, and countries) used in maps. When you view a map in Autodesk MapGuide Author or the Autodesk MapGuide Viewer, requests are sent to Autodesk MapGuide Server, which reads the SDF and sends the correct map data back to the client for display. Note that if a map layer contains points or text, the data may come from an SQL database instead of an SDF