Defined graphical sources tell the geospatial project where registered features can be located. They can be part of a reference file index, in which case the features are located in a series of files located and indexed by the file index. Or they may be located in a spatial data source defined by one of the supported spatial data sources. Features for spatial data sources are registered to that source by reading the source and identifying valid features. These features can then be given symbology and placement methods in the Features section of the project.