The Spatial Data File (SDF) is a single-user geodatabase file format developed by Autodesk. The file format is the native spatial data storage format for Autodesk GIS programs MapGuide and AutoCAD Map 3D. As of 2014 SDF format version SDF3 uses a single file. Prior versions of the format required a spatial index file (SIF), with an optional key index file (KIF) to speed access to the file.