Index: units/visits/visits_tag_processor.php
===================================================================
--- units/visits/visits_tag_processor.php	(revision 13557)
+++ units/visits/visits_tag_processor.php	(working copy)
@@ -18,7 +18,7 @@
 
 		function UserFound($params)
 		{
-			$virtual_users = Array(-1,-2, 0);
+			$virtual_users = Array(USER_ROOT, USER_GUEST, 0);
 			$object =& $this->Application->recallObject( $this->getPrefixSpecial(), $this->Prefix, $params );
 			return !in_array( $object->GetDBField( $params['user_field'] ) , $virtual_users );
 		}
Index: units/visits/visits_config.php
===================================================================
--- units/visits/visits_config.php	(revision 13557)
+++ units/visits/visits_config.php	(working copy)
@@ -85,10 +85,10 @@
 
 					'CalculatedFields' => Array (
 								'' => Array (
-										'UserName'	=>	'IF( ISNULL(u.Login), IF (%1$s.PortalUserId = -1, \'root\', IF (%1$s.PortalUserId = -2, \'Guest\', \'n/a\')), u.Login)',
+										'UserName'	=>	'IF( ISNULL(u.Login), IF (%1$s.PortalUserId = ' . USER_ROOT . ', \'root\', IF (%1$s.PortalUserId = ' . USER_GUEST . ', \'Guest\', \'n/a\')), u.Login)',
 									),
 								'incommerce' => Array (
-										'UserName'	=>	'IF( ISNULL(u.Login), IF (%1$s.PortalUserId = -1, \'root\', IF (%1$s.PortalUserId = -2, \'Guest\', \'n/a\')), u.Login)',
+										'UserName'	=>	'IF( ISNULL(u.Login), IF (%1$s.PortalUserId = ' . USER_ROOT . ', \'root\', IF (%1$s.PortalUserId = ' . USER_GUEST . ', \'Guest\', \'n/a\')), u.Login)',
 										'AffiliateUser'				=>	'IF( LENGTH(au.Login),au.Login,\'!la_None!\')',
 										'AffiliatePortalUserId'		=>	'af.PortalUserId',
 										'OrderTotalAmount'			=>	'IF(ord.Status = 4, ord.SubTotal+ord.ShippingCost+ord.VAT, 0)',
@@ -134,7 +134,7 @@
 										'Referer' => Array ('type' => 'string','not_null' => '1','default' => ''),
             							'IPAddress' => Array ('type' => 'string','not_null' => '1','default' => ''),
 										'AffiliateId' => Array ('type' => 'int','formatter' => 'kLEFTFormatter', 'error_msgs' => Array ('invalid_option' => '!la_error_UserNotFound!'), 'options' => Array (0 => 'lu_None'), 'left_sql' => 'SELECT %s FROM '.TABLE_PREFIX.'Affiliates af LEFT JOIN '.TABLE_PREFIX.'PortalUser pu ON pu.PortalUserId = af.PortalUserId WHERE `%s` = \'%s\'','left_key_field' => 'AffiliateId','left_title_field' => 'Login','not_null'=>1,'default'=>0),
-										'PortalUserId' => Array ('type' => 'int','not_null' => '1','default' => -2),
+										'PortalUserId' => Array ('type' => 'int','not_null' => '1','default' => USER_GUEST),
 							    ),
 
 					'VirtualFields'	=> 	Array (
Index: units/users/users_tag_processor.php
===================================================================
--- units/users/users_tag_processor.php	(revision 13557)
+++ units/users/users_tag_processor.php	(working copy)
@@ -211,7 +211,7 @@
 		function LoginName($params)
 		{
 			$object =& $this->getObject($params);
-			return $object->GetID() != -1 ? $object->GetDBField('Login') : 'root';
+			return $object->GetID() != USER_ROOT ? $object->GetDBField('Login') : 'root';
 		}
 
 		function CookieUsername($params)
Index: units/users/users_event_handler.php
===================================================================
--- units/users/users_event_handler.php	(revision 13559)
+++ units/users/users_event_handler.php	(working copy)
@@ -108,7 +108,7 @@
 				$user_id = $this->Application->RecallVar('user_id');
 				$items_info = $this->Application->GetVar($event->getPrefixSpecial(true));
 
-				if ($event->Name == 'OnCreate' && $user_id == -2) {
+				if ($event->Name == 'OnCreate' && $user_id == USER_GUEST) {
 					// "Guest" can create new users
 					return true;
 				}
@@ -226,7 +226,7 @@
 					$object->SetError('ValidateLogin', 'no_permission', 'lu_no_permissions');
 				}
 				else {
-					$object->SetID(-2);
+					$object->SetID(USER_GUEST);
 					$object->SetError('ValidateLogin', 'invalid_password', 'la_invalid_password');
 				}
 
@@ -1122,7 +1122,7 @@
 			if (!$items_info) return ;
 			list ($id, $field_values) = each($items_info);
 			$user_id = $this->Application->RecallVar('user_id');
-			if ($id == $user_id && ($user_id > 0 || $user_id == -1)) {
+			if ($id == $user_id && ($user_id > 0 || $user_id == USER_ROOT)) {
 				$user_dummy =& $this->Application->recallObject($event->Prefix.'.-item', null, Array('skip_autoload' => true));
 				/* @var $user_dummy kDBItem */
 
@@ -1135,7 +1135,7 @@
 				}
 			}
 
-			if ($user_id == -1) {
+			if ($user_id == USER_ROOT) {
 				$object =& $event->getObject( Array('skip_autoload' => true) );
 				/* @var $object UsersItem */
 
@@ -1251,7 +1251,7 @@
 				return true;
 			}
 
-			$virtual_users = Array (-1, -2); // root, Guest
+			$virtual_users = Array (USER_ROOT, USER_GUEST);
 			return ($object->GetDBField('Status') == STATUS_ACTIVE) || in_array($object->GetID(), $virtual_users);
 		}
 
Index: units/structure/structure_config.php
===================================================================
--- units/structure/structure_config.php	(revision 13557)
+++ units/structure/structure_config.php	(working copy)
@@ -138,7 +138,7 @@
             'MetaKeywords'				=>	Array('type' => 'string', 'default' => null),
             'CachedDescendantCatsQty'	=>	Array('type' => 'int', 'default' => 0),
             'CachedNavbar'				=>	Array('type' => 'string', 'formatter' => 'kMultiLanguage', 'default' => null),
-            'CreatedById'				=>	Array('type' => 'int', 'formatter' => 'kLEFTFormatter', 'options' => Array(-1 => 'root', -2 => 'Guest'),'left_sql'=>'SELECT %s FROM '.TABLE_PREFIX.'PortalUser WHERE `%s` = \'%s\'', 'left_key_field' => 'PortalUserId', 'left_title_field' => 'Login', 'not_null' => 1,'default' => 0),
+            'CreatedById'				=>	Array('type' => 'int', 'formatter' => 'kLEFTFormatter', 'options' => Array(USER_ROOT => 'root', USER_GUEST => 'Guest'),'left_sql'=>'SELECT %s FROM '.TABLE_PREFIX.'PortalUser WHERE `%s` = \'%s\'', 'left_key_field' => 'PortalUserId', 'left_title_field' => 'Login', 'not_null' => 1,'default' => 0),
             'ResourceId'				=>	Array('type' => 'int', 'default' => null),
             'ParentPath'				=>	Array('type' => 'string', 'default' => null),
 		    'TreeLeft'					=>	Array ('type' => 'int', 'not_null' => 1, 'default' => 0),
@@ -149,7 +149,7 @@
             'NewItem'					=>	Array('type' => 'int', 'formatter' => 'kOptionsFormatter', 'options' => Array (2 => 'la_Auto', 1 => 'la_Always', 0 => 'la_Never'), 'use_phrases' => 1,  'not_null' => 1, 'default' => 2),
             'PopItem'					=>	Array('type' => 'int', 'formatter' => 'kOptionsFormatter', 'options' => Array (2 => 'la_Auto', 1 => 'la_Always', 0 => 'la_Never'), 'use_phrases' => 1,  'not_null' => 1, 'default' => 2),
             'Modified'					=>	Array('type' => 'int', 'formatter' => 'kDateFormatter', 'default' => '#NOW#'),
-            'ModifiedById'				=>	Array('type' => 'int', 'formatter' => 'kLEFTFormatter', 'options' => Array(-1 => 'root', -2 => 'Guest'),'left_sql'=>'SELECT %s FROM '.TABLE_PREFIX.'PortalUser WHERE `%s` = \'%s\'', 'left_key_field' => 'PortalUserId', 'left_title_field' => 'Login', 'not_null' => 1,'default' => 0),
+            'ModifiedById'				=>	Array('type' => 'int', 'formatter' => 'kLEFTFormatter', 'options' => Array(USER_ROOT => 'root', USER_GUEST => 'Guest'),'left_sql'=>'SELECT %s FROM '.TABLE_PREFIX.'PortalUser WHERE `%s` = \'%s\'', 'left_key_field' => 'PortalUserId', 'left_title_field' => 'Login', 'not_null' => 1,'default' => 0),
             'CachedTemplate'			=>	Array('type' => 'string', 'not_null' => 1, 'default' => ''),
 
 
Index: units/reviews/reviews_config.php
===================================================================
--- units/reviews/reviews_config.php	(revision 13557)
+++ units/reviews/reviews_config.php	(working copy)
@@ -69,17 +69,17 @@
 
 		'CalculatedFields' => Array (
 			'' => Array (
-					'ReviewedBy' => 'IF( ISNULL(pu.Login), IF (%1$s.CreatedById = -1, \'root\', IF (%1$s.CreatedById = -2, \'Guest\', \'n/a\')), pu.Login )',
+					'ReviewedBy' => 'IF( ISNULL(pu.Login), IF (%1$s.CreatedById = ' . USER_ROOT . ', \'root\', IF (%1$s.CreatedById = ' . USER_GUEST . ', \'Guest\', \'n/a\')), pu.Login )',
 			),
 
 			'products' => Array (
-				'ReviewedBy'	=>	'IF( ISNULL(pu.Login), IF (%1$s.CreatedById = -1, \'root\', IF (%1$s.CreatedById = -2, \'Guest\', \'n/a\')), pu.Login )',
+				'ReviewedBy'	=>	'IF( ISNULL(pu.Login), IF (%1$s.CreatedById = ' . USER_ROOT . ', \'root\', IF (%1$s.CreatedById = ' . USER_GUEST . ', \'Guest\', \'n/a\')), pu.Login )',
 				'ItemName'		=>	'pr.l1_Name',
 				'ProductId'		=>	'pr.ProductId',
 			),
 
 			'product' => Array (
-				'ReviewedBy'	=>	'IF( ISNULL(pu.Login), IF (%1$s.CreatedById = -1, \'root\', IF (%1$s.CreatedById = -2, \'Guest\', \'n/a\')), pu.Login )',
+				'ReviewedBy'	=>	'IF( ISNULL(pu.Login), IF (%1$s.CreatedById = ' . USER_ROOT . ', \'root\', IF (%1$s.CreatedById = ' . USER_GUEST . ', \'Guest\', \'n/a\')), pu.Login )',
 				'ItemName'		=>	'pr.l1_Name',
 				'ProductId'		=>	'pr.ProductId',
 			),
@@ -146,12 +146,12 @@
 		    'CreatedById' => Array (
 		    	'type' => 'int',
 		    	'formatter' => 'kLEFTFormatter',
-			 	'options' => Array (-1 => 'root', -2 => 'Guest'),
+			 	'options' => Array (USER_ROOT => 'root', USER_GUEST => 'Guest'),
 			 	'left_sql' => 'SELECT %s FROM ' . TABLE_PREFIX . 'PortalUser
 			 						WHERE `%s` = \'%s\'	',
 			 	'left_key_field' => 'PortalUserId',
 			 	'left_title_field' => 'Login',
-				'required' => 1, 'not_null' => 1, 'default' => -1,
+				'required' => 1, 'not_null' => 1, 'default' => USER_ROOT,
 		    	'error_msgs' => Array ('invalid_option' => '!la_error_UserNotFound!'),
 			),
 		    'ItemType' => Array ('type' => 'int', 'not_null' => 1, 'default' => 0),
Index: units/modules/modules_tag_processor.php
===================================================================
--- units/modules/modules_tag_processor.php	(revision 13557)
+++ units/modules/modules_tag_processor.php	(working copy)
@@ -23,7 +23,7 @@
 
 		function _hasPrivileges()
 		{
-			return $this->Application->RecallVar('user_id') == -1;
+			return $this->Application->RecallVar('user_id') == USER_ROOT;
 		}
 
 		function AlreadyInstalled($params)
Index: units/modules/modules_event_handler.php
===================================================================
--- units/modules/modules_event_handler.php	(revision 13557)
+++ units/modules/modules_event_handler.php	(working copy)
@@ -117,7 +117,7 @@
 			parent::OnAfterListQuery($event);
 
 			$new_modules = $this->_getNewModules();
-			if (!$new_modules || $this->Application->RecallVar('user_id') != -1) {
+			if (!$new_modules || $this->Application->RecallVar('user_id') != USER_ROOT) {
 				return ;
 			}
 
Index: units/mailing_lists/mailing_lists_config.php
===================================================================
--- units/mailing_lists/mailing_lists_config.php	(revision 13557)
+++ units/mailing_lists/mailing_lists_config.php	(working copy)
@@ -97,9 +97,9 @@
 			'PortalUserId' => Array(
 				'type' => 'int',
 				'formatter' => 'kLEFTFormatter',
-				'options' => Array (-1 => 'root'),
+				'options' => Array (USER_ROOT => 'root'),
 				'left_sql' => 'SELECT %s FROM ' . TABLE_PREFIX . 'PortalUser WHERE `%s` = \'%s\'', 'left_key_field' => 'PortalUserId', 'left_title_field' => 'Login',
-				'required' => 1, 'not_null' => 1, 'default' => -1,
+				'required' => 1, 'not_null' => 1, 'default' => USER_ROOT,
 			),
 
 			'To' => Array ('type' => 'string', 'required' => 1, 'default' => NULL),
Index: units/logs/session_logs/session_logs_config.php
===================================================================
--- units/logs/session_logs/session_logs_config.php	(revision 13557)
+++ units/logs/session_logs/session_logs_config.php	(working copy)
@@ -75,7 +75,7 @@
 
 		'CalculatedFields' => Array(
 			'' => Array(
-				'UserLogin' => 'IF(%1$s.PortalUserId=-1, \'root\', u.Login)',
+				'UserLogin' => 'IF(%1$s.PortalUserId = ' . USER_ROOT . ', \'root\', u.Login)',
 				'UserFirstName' => 'u.FirstName',
 				'UserLastName' => 'u.LastName',
 				'UserEmail' => 'u.Email',
Index: units/logs/change_logs/change_logs_config.php
===================================================================
--- units/logs/change_logs/change_logs_config.php	(revision 13557)
+++ units/logs/change_logs/change_logs_config.php	(working copy)
@@ -89,7 +89,7 @@
 
 		'CalculatedFields' => Array (
 			'' => Array (
-				'UserLogin' => 'IF(%1$s.PortalUserId = -1, \'root\', u.Login)',
+				'UserLogin' => 'IF(%1$s.PortalUserId = ' . USER_ROOT . ', \'root\', u.Login)',
 				'UserFirstName' => 'u.FirstName',
 				'UserLastName' => 'u.LastName',
 				'UserEmail' => 'u.Email',
Index: units/languages/languages_event_handler.php
===================================================================
--- units/languages/languages_event_handler.php	(revision 13559)
+++ units/languages/languages_event_handler.php	(working copy)
@@ -305,7 +305,7 @@
 				$this->Application->Session->SetField('Language', $language_id);
 
 				// remember last user language in administrative console
-				if ($this->Application->RecallVar('user_id') == -1) {
+				if ($this->Application->RecallVar('user_id') == USER_ROOT) {
 					$this->Application->StorePersistentVar('AdminLanguage', $language_id);
 				}
 				else {
@@ -504,10 +504,10 @@
 				'l' . $object->GetID() . '_Body' => NULL,
 			);
 			$this->Conn->doUpdate($fields_hash, $this->Application->getUnitOption('emailevents', 'TableName'), 1);
-			
+
 			// clean Phrases table
 			$fields_hash = Array (
-				'l' . $object->GetID() . '_Translation' => NULL,			
+				'l' . $object->GetID() . '_Translation' => NULL,
 			);
 			$this->Conn->doUpdate($fields_hash, $this->Application->getUnitOption('phrases', 'TableName'), 1);
 		}
Index: units/helpers/user_helper.php
===================================================================
--- units/helpers/user_helper.php	(revision 13557)
+++ units/helpers/user_helper.php	(working copy)
@@ -66,7 +66,7 @@
 				}
 
 				if (!$dry_run) {
-					$user_id = -1;
+					$user_id = USER_ROOT;
 					$object->Load($user_id);
 					$object->SetDBField('Login', 'root');
 					$this->Application->StoreVar('user_id', $user_id);
@@ -178,7 +178,7 @@
 
 			$this->Application->HandleEvent($dummy, 'session-log:OnEndSession');
 
-			$user_id = -2;
+			$user_id = USER_GUEST;
 			$this->Application->SetVar('u.current_id', $user_id);
 			$object =& $this->Application->recallObject('u.current', null, Array('skip_autoload' => true));
 			$object->Load($user_id);
@@ -263,7 +263,7 @@
 				return ;
 			}
 
-			$is_root = $this->Application->RecallVar('user_id') == -1;
+			$is_root = $this->Application->RecallVar('user_id') == USER_ROOT;
 
 			$object =& $this->getUserObject();
 
Index: units/helpers/spam_helper.php
===================================================================
--- units/helpers/spam_helper.php	(revision 13557)
+++ units/helpers/spam_helper.php	(working copy)
@@ -93,7 +93,7 @@
 			$user_id = $this->Application->RecallVar('user_id');
 
 			if ($user_id == 0) {
-				$user_id = -2;
+				$user_id = USER_GUEST;
 			}
 
 			$keys = Array (
Index: units/helpers/permissions_helper.php
===================================================================
--- units/helpers/permissions_helper.php	(revision 13557)
+++ units/helpers/permissions_helper.php	(working copy)
@@ -188,7 +188,7 @@
 			}
 			$event->setEventParam('raise_warnings', $raise_warnings);
 
-			$owner_id = -1; // owner is root if not detected
+			$owner_id = USER_ROOT; // owner is root if not detected
 			if (!$id) {
 				// item being created -> check by current (before editing started, saved in OnPreCreate event) category permissions
 				// note: category in session is placed on catalog data import start
@@ -522,7 +522,7 @@
 
 		function CheckUserPermission($user_id, $name, $type = 1, $cat_id = null)
 		{
-			if ($user_id == -1) {
+			if ($user_id == USER_ROOT) {
 				// "root" is allowed anywhere
 				return $name == 'SYSTEM_ACCESS.READONLY' ? 0 : 1;
 			}
Index: units/files/files_config.php
===================================================================
--- units/files/files_config.php	(revision 13557)
+++ units/files/files_config.php	(working copy)
@@ -90,7 +90,7 @@
 				'not_null' => 1, 'default' => 1,
 			),
 			'CreatedOn' => Array ('type' => 'int', 'formatter' => 'kDateFormatter', 'default' => '#NOW#'),
-			'CreatedById' => Array ('type' => 'int', 'not_null' => 1, 'default' => -1),
+			'CreatedById' => Array ('type' => 'int', 'not_null' => 1, 'default' => USER_ROOT),
 			'MimeType' => Array ('type' => 'string', 'max_len' => 255, 'not_null' => 1, 'default' => ''),
 		),
 
Index: units/categories/categories_tag_processor.php
===================================================================
--- units/categories/categories_tag_processor.php	(revision 13557)
+++ units/categories/categories_tag_processor.php	(working copy)
@@ -1942,7 +1942,7 @@
 	 */
 	function AllowedCategoriesJSON($params)
 	{
-		if ($this->Application->RecallVar('user_id') == -1) {
+		if ($this->Application->RecallVar('user_id') == USER_ROOT) {
 			$categories = true;
 		}
 		else {
Index: units/categories/categories_event_handler.php
===================================================================
--- units/categories/categories_event_handler.php	(revision 13557)
+++ units/categories/categories_event_handler.php	(working copy)
@@ -309,7 +309,7 @@
 			}
 
 			$object->addFilter('perm_filter', 'PermId = 1'); // check for CATEGORY.VIEW permission
-			if ($this->Application->RecallVar('user_id') != -1) {
+			if ($this->Application->RecallVar('user_id') != USER_ROOT) {
 				// apply permission filters to all users except "root"
 				$groups = explode(',',$this->Application->RecallVar('UserGroups'));
 				foreach ($groups as $group) {
Index: units/categories/categories_config.php
===================================================================
--- units/categories/categories_config.php	(revision 13557)
+++ units/categories/categories_config.php	(working copy)
@@ -338,7 +338,7 @@
 		    'MetaKeywords'				=>	Array ('type' => 'string', 'formatter' => 'kFormatter', 'using_fck' => 1, 'default' => null),
 		    'CachedDescendantCatsQty'	=>	Array ('type' => 'int', 'default' => 0),
 		    'CachedNavbar'				=>	Array ('type' => 'string', 'formatter' => 'kMultiLanguage', 'default' => null),
-		    'CreatedById'				=>	Array ('type' => 'int', 'formatter' => 'kLEFTFormatter', 'error_msgs' => Array ('invalid_option' => '!la_error_UserNotFound!'), 'options' => Array (-1 => 'root', -2 => 'Guest'),'left_sql'=>'SELECT %s FROM '.TABLE_PREFIX.'PortalUser WHERE `%s` = \'%s\'', 'left_key_field' => 'PortalUserId', 'left_title_field' => 'Login', 'not_null' => 1,'default' => 0),
+		    'CreatedById'				=>	Array ('type' => 'int', 'formatter' => 'kLEFTFormatter', 'error_msgs' => Array ('invalid_option' => '!la_error_UserNotFound!'), 'options' => Array (USER_ROOT => 'root', USER_GUEST => 'Guest'),'left_sql'=>'SELECT %s FROM '.TABLE_PREFIX.'PortalUser WHERE `%s` = \'%s\'', 'left_key_field' => 'PortalUserId', 'left_title_field' => 'Login', 'not_null' => 1,'default' => 0),
 		    'ResourceId'				=>	Array ('type' => 'int', 'default' => null),
 		    'ParentPath'				=>	Array ('type' => 'string', 'default' => null),
 		    'TreeLeft'					=>	Array ('type' => 'int', 'not_null' => 1, 'default' => 0),
@@ -349,7 +349,7 @@
 		    'NewItem'					=>	Array ('type' => 'int', 'formatter' => 'kOptionsFormatter', 'options' => Array (2 => 'la_Auto', 1 => 'la_Always', 0 => 'la_Never'), 'use_phrases' => 1,  'not_null' => 1, 'default' => 2),
 		    'PopItem'					=>	Array ('type' => 'int', 'formatter' => 'kOptionsFormatter', 'options' => Array (2 => 'la_Auto', 1 => 'la_Always', 0 => 'la_Never'), 'use_phrases' => 1,  'not_null' => 1, 'default' => 2),
 		    'Modified'					=>	Array ('type' => 'int', 'formatter' => 'kDateFormatter', 'default' => '#NOW#'),
-		    'ModifiedById'				=>	Array ('type' => 'int', 'formatter' => 'kLEFTFormatter', 'error_msgs' => Array ('invalid_option' => '!la_error_UserNotFound!'), 'options' => Array (-1 => 'root', -2 => 'Guest'),'left_sql'=>'SELECT %s FROM '.TABLE_PREFIX.'PortalUser WHERE `%s` = \'%s\'', 'left_key_field' => 'PortalUserId', 'left_title_field' => 'Login', 'not_null' => 1,'default' => 0),
+		    'ModifiedById'				=>	Array ('type' => 'int', 'formatter' => 'kLEFTFormatter', 'error_msgs' => Array ('invalid_option' => '!la_error_UserNotFound!'), 'options' => Array (USER_ROOT => 'root', USER_GUEST => 'Guest'),'left_sql'=>'SELECT %s FROM '.TABLE_PREFIX.'PortalUser WHERE `%s` = \'%s\'', 'left_key_field' => 'PortalUserId', 'left_title_field' => 'Login', 'not_null' => 1,'default' => 0),
 		    'CachedTemplate'			=>	Array ('type' => 'string', 'not_null' => 1, 'default' => ''),
 
 
Index: kernel/utility/temp_handler.php
===================================================================
--- kernel/utility/temp_handler.php	(revision 13557)
+++ kernel/utility/temp_handler.php	(working copy)
@@ -949,8 +949,8 @@
 		if ($sids) {
 			// detect who is it
 			$sql = 'SELECT
-						CONCAT(IF (s.PortalUserId = -1, \'root\',
-							IF (s.PortalUserId = -2, \'Guest\',
+						CONCAT(IF (s.PortalUserId = ' . USER_ROOT . ', \'root\',
+							IF (s.PortalUserId = ' . USER_GUEST . ', \'Guest\',
 								CONCAT(FirstName, \' \', LastName, \' (\', Login, \')\')
 							)
 						), \' IP: \', s.IpAddress, \'\') FROM ' . TABLE_PREFIX . 'UserSession AS s
Index: kernel/startup.php
===================================================================
--- kernel/startup.php	(revision 13557)
+++ kernel/startup.php	(working copy)
@@ -167,6 +167,6 @@
 		include_once(KERNEL_PATH . '/utility/adodb-time.inc.php');
 	}
 
-	// global constants
-	define ('KG_TO_POUND', 2.20462262);
-	define ('POUND_TO_KG', 0.45359237);
\ No newline at end of file
+	// system users
+	define('USER_ROOT', -1);
+	define('USER_GUEST', -2);
\ No newline at end of file
Index: kernel/session/session.php
===================================================================
--- kernel/session/session.php	(revision 13557)
+++ kernel/session/session.php	(working copy)
@@ -353,7 +353,7 @@
 	function LoadPersistentVars(&$session)
 	{
 		$user_id = $session->RecallVar('user_id');
-		if ($user_id != -2) {
+		if ($user_id != USER_GUEST) {
 			// root & normal users
 			$sql = 'SELECT VariableValue, VariableName
 					FROM '.TABLE_PREFIX.'PersistantSessionData
@@ -375,7 +375,7 @@
 	function StorePersistentVar(&$session, $var_name, $var_value)
 	{
 		$user_id = $session->RecallVar('user_id');
-		if ($user_id == -2 || $user_id === false) {
+		if ($user_id == USER_GUEST || $user_id === false) {
 			// -2 (when not logged in), false (when after u:OnLogout event)
 			$session->StoreVar($var_name, $var_value);
 			return ;
@@ -414,7 +414,7 @@
 	 */
 	function RecallPersistentVar(&$session, $var_name, $default = false)
 	{
-		if ($session->RecallVar('user_id') == -2) {
+		if ($session->RecallVar('user_id') == USER_GUEST) {
 			if ($default == ALLOW_DEFAULT_SETTINGS) {
 				$default = null;
 			}
@@ -427,7 +427,7 @@
 		elseif ($default == ALLOW_DEFAULT_SETTINGS) {
 			$default_user_id = $this->Application->ConfigValue('DefaultSettingsUserId');
 			if (!$default_user_id) {
-				$default_user_id = -1;
+				$default_user_id = USER_ROOT;
 			}
 			$sql = 'SELECT VariableValue, VariableName
 					FROM '.TABLE_PREFIX.'PersistantSessionData
@@ -450,7 +450,7 @@
 
 		$user_id = $session->RecallVar('user_id');
 
-		if ($user_id != -2) {
+		if ($user_id != USER_GUEST) {
 			$sql = 'DELETE FROM '.TABLE_PREFIX.'PersistantSessionData
 					WHERE PortalUserId = '.$user_id.' AND VariableName = '.$this->Conn->qstr($var_name);
 			$this->Conn->Query($sql);
@@ -1398,7 +1398,7 @@
 		$user_id = $this->RecallVar('user_id');
 
 		$ret = $user_id > 0;
-		if (($this->RecallVar('admin') == 1 || defined('ADMIN')) && ($user_id == -1)) {
+		if (($this->RecallVar('admin') == 1 || defined('ADMIN')) && ($user_id == USER_ROOT)) {
 			$ret = true;
 		}
 		return $ret;
Index: kernel/session/inp_session.php
===================================================================
--- kernel/session/inp_session.php	(revision 13557)
+++ kernel/session/inp_session.php	(working copy)
@@ -114,7 +114,7 @@
 	function StoreSession(&$session, $additional_fields = Array())
 	{
 		$fields_hash = Array (
-			'PortalUserId'	=>	$this->Application->isAdmin ? 0 : -2, // Guest
+			'PortalUserId'	=>	$this->Application->isAdmin ? 0 : USER_GUEST,
 			'Language'		=>	$this->Application->GetDefaultLanguageId(true),
 			'Theme'			=>	$this->Application->GetDefaultThemeId(),
 			'IpAddress'		=>	$_SERVER['REMOTE_ADDR'], // getenv('REMOTE_ADDR') won't work on IIS, so use $_SERVER instead
Index: kernel/event_manager.php
===================================================================
--- kernel/event_manager.php	(revision 13557)
+++ kernel/event_manager.php	(working copy)
@@ -412,7 +412,7 @@
 				}
 
 				$event->setEventParam('top_prefix', $this->Application->GetTopmostPrefix($event->Prefix, true));
-				if (($this->Application->RecallVar('user_id') == -1) || $event_handler->CheckPermission($event)) {
+				if (($this->Application->RecallVar('user_id') == USER_ROOT) || $event_handler->CheckPermission($event)) {
 					$this->HandleEvent($event);
 				}
 
@@ -744,7 +744,7 @@
 			$events_source = $agents[$event_type];
 
 			$user_id = $this->Application->RecallVar('user_id');
-			$this->Application->StoreVar('user_id', -1, true); // to prevent permission checking inside events, true for optional storage
+			$this->Application->StoreVar('user_id', USER_ROOT, true); // to prevent permission checking inside events, true for optional storage
 
 			foreach ($events_source as $short_name => $event_data) {
 				$next_run = $event_data['NextRunOn'];
Index: kernel/event_handler.php
===================================================================
--- kernel/event_handler.php	(revision 13557)
+++ kernel/event_handler.php	(working copy)
@@ -187,6 +187,7 @@
 		function CheckPermission(&$event)
 		{
 			$perm_helper =& $this->Application->recallObject('PermissionsHelper');
+			/* @var $perm_helper kPermissionsHelper */
 
 			return $perm_helper->CheckEventPermission($event, $this->permMapping);
 		}
Index: kernel/db/db_event_handler.php
===================================================================
--- kernel/db/db_event_handler.php	(revision 13557)
+++ kernel/db/db_event_handler.php	(working copy)
@@ -533,14 +533,14 @@
 				$user_id = $this->Application->RecallVar('user_id');
 				$event->setEventParam('top_prefix', $this->Application->GetTopmostPrefix($event->Prefix, true));
 				$status_checked = false;
-				if ($user_id == -1 || $this->CheckPermission($event)) {
+				if ($user_id == USER_ROOT || $this->CheckPermission($event)) {
 					// don't autoload item, when user doesn't have view permission
 					$this->LoadItem($event);
 
 					$status_checked = true;
 					$editing_mode = defined('EDITING_MODE') ? EDITING_MODE : false;
 
-					if ($user_id != -1 && !$this->Application->isAdmin && !($editing_mode || $this->checkItemStatus($event))) {
+					if ($user_id != USER_ROOT && !$this->Application->isAdmin && !($editing_mode || $this->checkItemStatus($event))) {
 						// non-root user AND on front-end AND (not editing mode || incorrect status)
 						$perm_status = false;
 					}
@@ -2647,7 +2647,7 @@
 			$admin_ses =& $this->Application->recallObject('Session.admin');
 			/* @var $admin_ses Session */
 
-			if ($admin_ses->RecallVar('user_id') == -1) {
+			if ($admin_ses->RecallVar('user_id') == USER_ROOT) {
 				return true;
 			}
 
Index: kernel/db/cat_tag_processor.php
===================================================================
--- kernel/db/cat_tag_processor.php	(revision 13557)
+++ kernel/db/cat_tag_processor.php	(working copy)
@@ -890,7 +890,7 @@
 		 */
 		function AllowedCategoriesJSON($params)
 		{
-			if ($this->Application->RecallVar('user_id') == -1) {
+			if ($this->Application->RecallVar('user_id') == USER_ROOT) {
 				$categories = true;
 			}
 			else {
Index: kernel/db/cat_event_handler.php
===================================================================
--- kernel/db/cat_event_handler.php	(revision 13557)
+++ kernel/db/cat_event_handler.php	(working copy)
@@ -608,7 +608,7 @@
 		}
 
 		// add permission filter
-		if ($this->Application->RecallVar('user_id') == -1) {
+		if ($this->Application->RecallVar('user_id') == USER_ROOT) {
 			// for "root" CATEGORY.VIEW permission is checked for items lists too
 			$view_perm = 1;
 		}
Index: kernel/constants.php
===================================================================
--- kernel/constants.php	(revision 13559)
+++ kernel/constants.php	(working copy)
@@ -166,4 +166,7 @@
 
 	// site domains
 	define('SITE_DOMAIN_REDIRECT_CURRENT', 1);
-	define('SITE_DOMAIN_REDIRECT_EXTERNAL', 2);
\ No newline at end of file
+	define('SITE_DOMAIN_REDIRECT_EXTERNAL', 2);
+
+	define ('KG_TO_POUND', 2.20462262);
+	define ('POUND_TO_KG', 0.45359237);
Index: kernel/application.php
===================================================================
--- kernel/application.php	(revision 13559)
+++ kernel/application.php	(working copy)
@@ -2212,8 +2212,8 @@
 		$session =& $this->recallObject('Session');
 		$user_id = $session->GetField('PortalUserId');
 
-		if (!$user_id && $user_id != -1) {
-			$user_id = -2;
+		if (!$user_id && $user_id != USER_ROOT) {
+			$user_id = USER_GUEST;
 		}
 
 		$this->SetVar('u.current_id', $user_id);
@@ -2223,7 +2223,7 @@
 			$this->SetVar('u_id', $user_id);
 		}
 
-		$this->StoreVar('user_id', $user_id, $user_id == -2); // storing Guest user_id (-2) is optional
+		$this->StoreVar('user_id', $user_id, $user_id == USER_GUEST); // storing Guest user_id (-2) is optional
 
 		$this->isAdminUser = $this->isAdmin && $this->LoggedIn();
 
@@ -2233,12 +2233,12 @@
 			$user->SetError('ValidateLogin', 'session_expired', 'la_text_sess_expired');
 		}
 
-		if (($user_id != -2) && constOn('DBG_REQUREST_LOG') ) {
+		if (($user_id != USER_GUEST) && constOn('DBG_REQUREST_LOG') ) {
 			$http_query =& $this->recallObject('HTTPQuery');
 			$http_query->writeRequestLog(DBG_REQUREST_LOG);
 		}
 
-		if ($user_id != -2) {
+		if ($user_id != USER_GUEST) {
 			// normal users + root
 			$this->LoadPersistentVars();
 		}
@@ -3081,11 +3081,11 @@
 	function getUserGroups($user_id)
 	{
 		switch ($user_id) {
-			case -1:
+			case USER_ROOT:
 				$user_groups = $this->ConfigValue('User_LoggedInGroup');
 				break;
 
-			case -2:
+			case USER_GUEST:
 				$user_groups = $this->ConfigValue('User_LoggedInGroup') . ',' . $this->ConfigValue('User_GuestGroup');
 				break;
 
Index: install.php
===================================================================
--- install.php	(revision 13557)
+++ install.php	(working copy)
@@ -354,7 +354,7 @@
 							}
 
 							if ($this->errorMessage == '') {
-								$user_id = -1;
+								$user_id = USER_ROOT;
 								$session =& $this->Application->recallObject('Session');
 								$session->SetField('PortalUserId', $user_id);
 								$this->Application->SetVar('u.current_id', $user_id);
@@ -573,7 +573,7 @@
 
 						$fields_hash = Array (
 							'l1_Name' => 'Content', 'Filename' => 'Content', 'AutomaticFilename' => 0,
-							'CreatedById' => -1, 'CreatedOn' => time(), 'ResourceId' => $resource_id - 1,
+							'CreatedById' => USER_ROOT, 'CreatedOn' => time(), 'ResourceId' => $resource_id - 1,
 							'l1_Description' => 'Content', 'Status' => 4,
 						);