Example:
SharedLocationMappings globalLocationMappings = SharedLocationMappings( new LocationMappings );
// now the map could get set by hand, but thats not needed:
ShaderProgramFileManager::the()->get( ShaderProgramControlFiles("shader1").
                                      externAttributeLocations(globalLocationMappings) );
// will add all maps from the shader1 to the global map
ShaderProgramFileManager::the()->get( ShaderProgramControlFiles("shader2").
                                      externAttributeLocations(globalLocationMappings) );
// will add all maps from shader2, attributes already known will not get changed, no location collitions.

Reloading of the shaders due to changed files will automatically set the locations again.