public static function SelectModule($sModuleName)
 {
     if (!class_exists($sModuleName)) {
         throw new CoreException("Could not select this module, '{$sModuleName}' in not a valid class name");
         return;
     }
     if (!is_subclass_of($sModuleName, 'UserRightsAddOnAPI')) {
         throw new CoreException("Could not select this module, the class '{$sModuleName}' is not derived from UserRightsAddOnAPI");
         return;
     }
     self::$m_oAddOn = new $sModuleName();
     self::$m_oAddOn->Init();
     self::$m_oUser = null;
     self::$m_oRealUser = null;
 }