This task entry refers to a method that does not exist! When the method will be implemented it has to be non static!
        {
                global $ilias;
                require_once('Services/WebDAV/classes/class.ilDiskQuotaActivationChecker.php');
                require_once('Services/Payment/classes/class.ilUserDefinedInvoiceNumber.php');
                $this->default_tasks = array(
                                'ilLDAPCronSynchronization::start',
                                'ilCronCheckUserAccounts::check',
                                'ilLuceneIndexer::index',
                                'ilCronLinkCheck::check',
                                'ilCronWebResourceCheck::check',
                                'ilCronForumNotification::sendNotifications',
                                'ilCronMailNotification::sendNotifications',
                                'ilCronValidator::check',
                                'ilCronDiskQuotaCheck::updateDiskUsageStatistics',
                                'ilCronDiskQuotaCheck::sendReminderMails',
                                
                                #'ilPaymentShoppingCart::__deleteExpiredSessionsPSC',
                                'ilCronDeleteInactiveUserAccounts::run',
                                'ilCronDeleteInactivatedUserAccounts::run',
                                'ilCronPaymentNotification::sendNotifications',
                                'ilCronCourseGroupNotification::check',
                                'ilCronPaymentUDInvoiceNumberReset::check',
                                'ilCronObjectStatisticsCheck::check'
                );
                $this->possible_tasks = array(
                                'ilLDAPCronSynchronization::start' => array(
                                        'classname'             => 'ilLDAPCronSynchronization',
                                        'method'                => 'start',
                                        'location'              => 'Services/LDAP',
                                        'condition'             => true
                                ),
                                
                                
                                'ilCronCheckUserAccounts::check' => array(
                                        'classname'             => 'ilCronCheckUserAccounts',
                                        'method'                => 'check',
                                        'location'              => 'cron',
                                        'condition'             => $ilias->getSetting('cron_user_check')
                                ),
                                
                                
                                'ilLuceneIndexer::index' => array(
                                        'classname'             => 'ilLuceneIndexer',
                                        'method'                => 'index',
                                        'location'              => 'Services/Search',
                                        'sub_location'  => 'Lucene',
                                        'condition'             => $ilias->getSetting("cron_lucene_index")
                                ),
                                
                                
                                'ilCronLinkCheck::check' => array(
                                        'classname'             => 'ilCronLinkCheck',
                                        'method'                => 'check',
                                        'location'              => 'cron',
                                        'condition'             => $ilias->getSetting("cron_link_check")
                                ),
                                
                                
                                'ilCronWebResourceCheck::check' => array(
                                        'classname'             => 'ilCronWebResourceCheck',
                                        'method'                => 'check',
                                        'location'              => 'cron',
                                        'condition'             => $ilias->getSetting("cron_web_resource_check")
                                ),
                                
                                
                                'ilCronForumNotification::sendNotifications' => array(
                                        'classname'             => 'ilCronForumNotification',
                                        'method'                => 'sendNotifications',
                                        'location'              => 'cron',
                                        'condition'             => ($ilias->getSetting('forum_notification') == 2)
                                ),
                                
                                
                                'ilCronMailNotification::sendNotifications' => array(
                                        'classname'             => 'ilCronMailNotification',
                                        'method'                => 'sendNotifications',
                                        'location'              => 'cron',
                                        'condition'             => ($ilias->getSetting('mail_notification') == 1)
                                ),
                                
                                
                                'ilCronValidator::check' => array(
                                        'classname'             => 'ilCronValidator',
                                        'method'                => 'check',
                                        'location'              => 'cron',
                                        'condition'             => ($ilias->getSetting('systemcheck_cron') == 1)
                                ),
                                
                                
                                'ilCronDiskQuotaCheck::updateDiskUsageStatistics' => array(
                                        'classname'             => 'ilCronDiskQuotaCheck',
                                        'method'                => 'updateDiskUsageStatistics',
                                        'location'              => 'cron',
                                ),
                                
                                
                                'ilCronDiskQuotaCheck::sendReminderMails' => array(
                                        'classname'             => 'ilCronDiskQuotaCheck',
                                        'method'                => 'sendReminderMails',
                                        'location'              => 'cron',
                                ),
                                
                                
                                'ilCronDiskQuotaCheck::sendSummaryMails' => array(
                                        'classname'             => 'ilCronDiskQuotaCheck',
                                        'method'                => 'sendSummaryMails',
                                        'location'              => 'cron',
                                ),
                                
                                #// Start Shopping Cart Check
                                #'ilPaymentShoppingCart::__deleteExpiredSessionsPSC' => array(
                                #       'classname'             => 'ilPaymentShoppingCart',
                                #       'method'                => '__deleteExpiredSessionsPSC',
                                #       'location'              => 'Services/Payment',
                                #       'condition'             => true
                                #),
                                
                                'ilCronDeleteInactiveUserAccounts::run' => array(
                                        'classname'             => 'ilCronDeleteInactiveUserAccounts',
                                        'method'                => 'run',
                                        'location'              => 'Services/User',
                                        'condition'             => $ilias->getSetting('cron_inactive_user_delete', 0)
                                ),
                                
                                'ilCronDeleteInactivatedUserAccounts::run' => array(
                                        'classname'             => 'ilCronDeleteInactivatedUserAccounts',
                                        'method'                => 'run',
                                        'location'              => 'Services/User',
                                        'condition'             => $ilias->getSetting('cron_inactivated_user_delete', 0)
                                ),
                                
                                'ilCronPaymentNotification::sendNotifications' => array(
                                        'classname'             => 'ilCronPaymentNotification',
                                        'method'                => 'sendNotifications',
                                        'location'              => 'cron',
                                        'condition'             => ($ilias->getSetting('payment_notifications') == 1)
                                ),
                                
                                'ilCronCourseGroupNotification::check' => array(
                                        'classname'             => 'ilCronCourseGroupNotification',
                                        'method'                => 'sendNotifications',
                                        'location'              => 'cron',
                                        'condition'             => $ilias->getSetting("crsgrp_ntf")
                                ),
                                
                                'ilCronPaymentUDInvoiceNumberReset::check' => array(
                                        'classname'             => 'ilCronPaymentUDInvoiceNumberReset',
                                        'method'                => 'check',
                                        'location'              => 'cron',
                                ),
                        
                                
                                'ilCronObjectStatisticsCheck::check' => array(
                                        'classname'             => 'ilCronObjectStatisticsCheck',
                                        'method'                => 'check',
                                        'location'              => 'cron',
                                        'condition'             => true
                                )
                );
        }