diff --git a/administrator/components/com_admin/sql/updates/mysql/4.0.0-2019-07-02.sql b/administrator/components/com_admin/sql/updates/mysql/4.0.0-2019-07-02.sql
new file mode 100644
index 0000000000000..41ab9cb4807aa
--- /dev/null
+++ b/administrator/components/com_admin/sql/updates/mysql/4.0.0-2019-07-02.sql
@@ -0,0 +1,2 @@
+ALTER TABLE `#__associations` ADD COLUMN `parent_id` int(11) NOT NULL DEFAULT -1 COMMENT 'The parent of an association.';
+ALTER TABLE `#__associations` ADD COLUMN `parent_date` datetime COMMENT 'The save or modified date of the parent.';
diff --git a/administrator/components/com_admin/sql/updates/postgresql/4.0.0-2019-07-02.sql b/administrator/components/com_admin/sql/updates/postgresql/4.0.0-2019-07-02.sql
new file mode 100644
index 0000000000000..25fc0fd66f80a
--- /dev/null
+++ b/administrator/components/com_admin/sql/updates/postgresql/4.0.0-2019-07-02.sql
@@ -0,0 +1,4 @@
+ALTER TABLE "#__associations" ADD COLUMN "parent_id" integer DEFAULT -1 NOT NULL;
+ALTER TABLE "#__associations" ADD COLUMN "parent_date" timestamp without time zone;
+COMMENT ON COLUMN "#__associations"."parent_id" IS 'The parent of an association.';
+COMMENT ON COLUMN "#__associations"."parent_date" IS 'The save or modified date of the parent.';
diff --git a/administrator/components/com_associations/Controller/AssociationsController.php b/administrator/components/com_associations/Controller/AssociationsController.php
index f5c362d5a3f01..f4e98420b8abd 100644
--- a/administrator/components/com_associations/Controller/AssociationsController.php
+++ b/administrator/components/com_associations/Controller/AssociationsController.php
@@ -49,7 +49,7 @@ public function getModel($name = 'Associations', $prefix = 'Administrator', $con
 	}
 
 	/**
-	 * Method to purge the associations table.
+	 * Method to purge the associations table by context.
 	 *
 	 * @return  void
 	 *
@@ -57,7 +57,8 @@ public function getModel($name = 'Associations', $prefix = 'Administrator', $con
 	 */
 	public function purge()
 	{
-		$this->getModel('associations')->purge();
+		$context = $this->input->getString('itemtype');
+		$this->getModel('associations')->purge($context);
 		$this->setRedirect(Route::_('index.php?option=' . $this->option . '&view=' . $this->view_list, false));
 	}
 
diff --git a/administrator/components/com_associations/Controller/DefaultAssocLangController.php b/administrator/components/com_associations/Controller/DefaultAssocLangController.php
new file mode 100644
index 0000000000000..843ef07ed4a37
--- /dev/null
+++ b/administrator/components/com_associations/Controller/DefaultAssocLangController.php
@@ -0,0 +1,41 @@
+<?php
+/**
+ * @package     Joomla.Administrator
+ * @subpackage  com_associations
+ *
+ * @copyright   Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+namespace Joomla\Component\Associations\Administrator\Controller;
+
+defined('_JEXEC') or die;
+
+use Joomla\CMS\MVC\Controller\BaseController;
+use Joomla\CMS\Router\Route;
+
+/**
+ * Association edit controller class.
+ *
+ * @since  4.0
+ */
+class DefaultAssocLangController extends BaseController
+{
+	/**
+	 * Method to update the childs modified date of the parent in the associations table.
+	 *
+	 * @return  void
+	 *
+	 * @since  4.0
+	 */
+	public function update()
+	{
+		$targetId = $this->input->get('targetId', '', 'int');
+		$parentId = $this->input->get('id', '', 'int');
+		$itemtype = $this->input->get('itemtype', '', 'string');
+
+		$this->getModel('defaultAssocLang')->update($targetId, $parentId, $itemtype);
+
+		$this->setRedirect(Route::_('index.php?option=com_associations&view=associations', false));
+	}
+}
diff --git a/administrator/components/com_associations/Field/ContentdefaultassoclangField.php b/administrator/components/com_associations/Field/ContentdefaultassoclangField.php
new file mode 100644
index 0000000000000..ebd884b414126
--- /dev/null
+++ b/administrator/components/com_associations/Field/ContentdefaultassoclangField.php
@@ -0,0 +1,68 @@
+<?php
+/**
+ * @package     Joomla.Administrator
+ * @subpackage  com_associations
+ *
+ * @copyright   Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+namespace Joomla\Component\Associations\Administrator\Field;
+
+defined('_JEXEC') or die;
+
+use Joomla\CMS\Form\Field\ContentlanguageField;
+use Joomla\CMS\HTML\HTMLHelper;
+use Joomla\CMS\Language\Associations;
+use Joomla\CMS\Language\LanguageHelper;
+use Joomla\CMS\Language\Text;
+use Joomla\Registry\Registry;
+
+
+/**
+ * Content Association Languages Field class.
+ *
+ * @since  4.0
+ */
+class ContentdefaultassoclangField extends ContentlanguageField
+{
+	/**
+	 * The list field type.
+	 *
+	 * @var    string
+	 *
+	 * @since  4.0
+	 */
+	public $type = 'contentdefaultassoclang';
+
+	/**
+	 * Method to get the field options.
+	 *
+	 * @return  array The field option objects.
+	 *
+	 * @since   4.0
+	 */
+	public function getOptions()
+	{
+		$defaultAssocLang = Associations::getDefaultAssocLang();
+		$contentLanguages = LanguageHelper::getContentLanguages(array(0, 1));
+
+		$options   = array();
+		$options[] = HTMLHelper::_('select.option', '', Text::_('JOPTION_SELECT_LANGUAGE'));
+
+		foreach ($contentLanguages as $langCode)
+		{
+			// Add information to the language if it is the default association language.
+			if ($langCode->lang_code == $defaultAssocLang)
+			{
+				$options[] = HTMLHelper::_('select.option', $langCode->lang_code, $langCode->title . ' - ' . Text::_('JGLOBAL_ASSOCIATIONS_DEFAULT_ASSOC_LANG'));
+			}
+			else
+			{
+				$options[] = HTMLHelper::_('select.option', $langCode->lang_code, $langCode->title);
+			}
+		}
+
+		return $options;
+	}
+}
diff --git a/administrator/components/com_associations/Field/ItemlanguageField.php b/administrator/components/com_associations/Field/ItemlanguageField.php
index 3f23450b9c8b9..903e2fc6f6c06 100644
--- a/administrator/components/com_associations/Field/ItemlanguageField.php
+++ b/administrator/components/com_associations/Field/ItemlanguageField.php
@@ -13,7 +13,9 @@
 
 use Joomla\CMS\Factory;
 use Joomla\CMS\Form\Field\ListField;
+use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Language\LanguageHelper;
+use Joomla\CMS\Language\Text;
 use Joomla\Component\Associations\Administrator\Helper\AssociationsHelper;
 use Joomla\Utilities\ArrayHelper;
 
@@ -62,6 +64,10 @@ protected function getOptions()
 		// Gets existing languages.
 		$existingLanguages = LanguageHelper::getContentLanguages(array(0, 1));
 
+		// Get default association language and check if reference is a parent.
+		$defaultAssocLang = Associations::getDefaultAssocLang();
+		$refIsParent      = $referenceLang === $defaultAssocLang;
+
 		$options = array();
 
 		// Each option has the format "<lang>|<id>", example: "en-GB|1"
@@ -73,9 +79,23 @@ protected function getOptions()
 				continue;
 			}
 
+			if ($defaultAssocLang && !$refIsParent)
+			{
+				// If reference is a child then display just the default association language
+				if ($language->lang_code !== $defaultAssocLang)
+				{
+					continue;
+				}
+			}
+
 			$options[$langCode]       = new \stdClass;
 			$options[$langCode]->text = $language->title;
 
+			if ($defaultAssocLang && ($language->lang_code === $defaultAssocLang))
+			{
+				$options[$langCode]->text .= ' - ' . Text::_('JGLOBAL_ASSOCIATIONS_DEFAULT_ASSOC_LANG');
+			}
+
 			// If association exists in this language.
 			if (isset($associations[$language->lang_code]))
 			{
diff --git a/administrator/components/com_associations/Helper/AssociationsHelper.php b/administrator/components/com_associations/Helper/AssociationsHelper.php
index ecdcc480311d4..424d6579efea8 100644
--- a/administrator/components/com_associations/Helper/AssociationsHelper.php
+++ b/administrator/components/com_associations/Helper/AssociationsHelper.php
@@ -13,8 +13,10 @@
 
 use Joomla\CMS\Association\AssociationExtensionInterface;
 use Joomla\CMS\Association\AssociationServiceInterface;
+use Joomla\CMS\Component\ComponentHelper;
 use Joomla\CMS\Factory;
 use Joomla\CMS\Helper\ContentHelper;
+use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Language\LanguageHelper;
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\Layout\LayoutHelper;
@@ -209,15 +211,18 @@ private static function getExtensionRealName($extensionName)
 	 * @param   string   $itemLanguage    Item language code.
 	 * @param   boolean  $addLink         True for adding edit links. False for just text.
 	 * @param   boolean  $assocLanguages  True for showing non associated content languages. False only languages with associations.
+	 * @param   string   $assocState      The filter association state, enabled when a default association language is used.
 	 *
 	 * @return  string   The language HTML
 	 *
 	 * @since  3.7.0
 	 */
-	public static function getAssociationHtmlList($extensionName, $typeName, $itemId, $itemLanguage, $addLink = true, $assocLanguages = true)
+	public static function getAssociationHtmlList($extensionName, $typeName, $itemId, $itemLanguage,
+		$addLink = true, $assocLanguages = true, $assocState = 'all'
+	)
 	{
 		// Get the associations list for this item.
-		$items = self::getAssociationList($extensionName, $typeName, $itemId);
+		$items   = self::getAssociationList($extensionName, $typeName, $itemId);
 
 		$titleFieldName = self::getTypeFieldName($extensionName, $typeName, 'title');
 
@@ -227,33 +232,64 @@ public static function getAssociationHtmlList($extensionName, $typeName, $itemId
 		$canEditReference = self::allowEdit($extensionName, $typeName, $itemId);
 		$canCreate        = self::allowAdd($extensionName, $typeName);
 
+		// Get the default association language, empty if not used
+		$defaultAssocLang = Associations::getDefaultAssocLang();
+
+		// Check if versions are enabled
+		$saveHistory      = ComponentHelper::getParams($extensionName)->get('save_history', 0);
+		$context          = ($typeName === 'category') ? 'com_categories.item' : $extensionName . '.item';
+
+		if ($items)
+		{
+			// Get parent dates of each item of an association and the parent id.
+			$assocParentDates = DefaultAssocLangHelper::getParentDates($items, $context);
+			$parentId = $items[$defaultAssocLang]['id'] ?? null;
+		}
+
 		// Create associated items list.
 		foreach ($languages as $langCode => $language)
 		{
-			// Don't do for the reference language.
-			if ($langCode == $itemLanguage)
-			{
-				continue;
-			}
+			// Defaults
+			$update     = false;
+			$parentChildInfo = '';
 
-			// Don't show languages with associations, if we don't want to show them.
-			if ($assocLanguages && isset($items[$langCode]))
+			if (!$defaultAssocLang)
 			{
-				unset($items[$langCode]);
-				continue;
-			}
+				// Don't do for the reference language.
+				if ($langCode == $itemLanguage)
+				{
+					continue;
+				}
 
-			// Don't show languages without associations, if we don't want to show them.
-			if (!$assocLanguages && !isset($items[$langCode]))
-			{
-				continue;
+				// Don't show languages with associations, if we don't want to show them.
+				if ($assocLanguages && isset($items[$langCode]))
+				{
+					unset($items[$langCode]);
+					continue;
+				}
+
+				// Don't show languages without associations, if we don't want to show them.
+				if (!$assocLanguages && !isset($items[$langCode]))
+				{
+					continue;
+				}
 			}
 
-			// Get html parameters.
+			// Get html parameters for associated items.
 			if (isset($items[$langCode]))
 			{
-				$title       = $items[$langCode][$titleFieldName];
-				$additional  = '';
+				if ($defaultAssocLang)
+				{
+					// Don't display any other children to the child item.
+					if (($itemLanguage !== $defaultAssocLang) && ($langCode !== $defaultAssocLang) && ($langCode !== $itemLanguage))
+					{
+						unset($items[$langCode]);
+						continue;
+					}
+				}
+
+				$title      = $items[$langCode][$titleFieldName];
+				$additional = '';
 
 				if (isset($items[$langCode]['catid']))
 				{
@@ -286,33 +322,150 @@ public static function getAssociationHtmlList($extensionName, $typeName, $itemId
 					$additional = '<strong>' . Text::sprintf('COM_MENUS_MENU_SPRINTF', $menutype_title) . '</strong><br>';
 				}
 
-				$labelClass  = 'badge-secondary';
+				$labelClass  = 'badge-success';
 				$target      = $langCode . ':' . $items[$langCode]['id'] . ':edit';
 				$allow       = $canEditReference
 								&& self::allowEdit($extensionName, $typeName, $items[$langCode]['id'])
 								&& self::canCheckinItem($extensionName, $typeName, $items[$langCode]['id']);
 
-				$additional .= $addLink && $allow ? Text::_('COM_ASSOCIATIONS_EDIT_ASSOCIATION') : '';
+				$parentChildInfoSpace = $additional && !$addLink ? '<br>' : '<br><br>';
+
+				if ($defaultAssocLang)
+				{
+					// Settings for the default association language.
+					if ($defaultAssocLang === $langCode)
+					{
+						$labelClass .= ' parent-item';
+						$additional .= $addLink && $allow ? Text::_('COM_ASSOCIATIONS_EDIT_ASSOCIATION') : '';
+						$parentChildInfo  = $parentChildInfoSpace . Text::_('JGLOBAL_ASSOCIATIONS_DEFAULT_ASSOC_LANG_ITEM');
+
+						if ($defaultAssocLang === $itemLanguage)
+						{
+							// Do not define any child target as there can be more than one
+							$target = '';
+						}
+						else
+						{
+							$target = $itemLanguage . ':' . $itemId . ':edit';
+						}
+					}
+					// Setting for children
+					else
+					{
+						// When there is no associated parent, set it to target
+						if (!$parentId)
+						{
+							$target        = $defaultAssocLang . ':0:add';
+						}
+
+						if (array_key_exists($items[$langCode]['id'], $assocParentDates) && array_key_exists($parentId, $assocParentDates))
+						{
+							$associatedModifiedParent = $assocParentDates[$items[$langCode]['id']][0];
+							$lastModifiedParent       = $assocParentDates[$parentId][0];
+
+							if ($associatedModifiedParent < $lastModifiedParent)
+							{
+								// Don't display not corresponding item
+								if ($assocState !== 'all' && $assocState !== 'out_of_date')
+								{
+									unset($items[$langCode]);
+									continue;
+								}
+
+								$additional .= $addLink && $allow ? Text::_('COM_ASSOCIATIONS_UPDATE_ASSOCIATION') : '';
+								$labelClass    = 'badge-warning';
+								$target = $langCode . ':' . $items[$langCode]['id'] . ':edit';
+								$update = true;
+
+								/*
+								When versions are disabled then the modified date is used for the parent.
+								That means that when no changes were made and the parent has been saved the modified date has been changed.
+								So the out-of-date state means in that case there might have been made changes and it is necessary to check manually and update the target.
+								*/
+								$parentChildInfo = $saveHistory
+									? $parentChildInfoSpace . Text::_('JGLOBAL_ASSOCIATIONS_STATE_OUT_OF_DATE_DESC')
+									: $parentChildInfoSpace . Text::_('JGLOBAL_ASSOCIATIONS_STATE_MIGHT_BE_OUT_OF_DATE_DESC');
+							}
+							else
+							{
+								// Don't display not corresponding item
+								if ($assocState !== 'all' && $assocState !== 'up_to_date')
+								{
+									unset($items[$langCode]);
+									continue;
+								}
+
+								$additional .= $addLink && $allow ? Text::_('COM_ASSOCIATIONS_EDIT_ASSOCIATION') : '';
+								$parentChildInfo  = $parentChildInfoSpace . Text::_('JGLOBAL_ASSOCIATIONS_STATE_UP_TO_DATE_DESC');
+
+								// For item types that do not use modified date or versions like menu items
+								if (!$associatedModifiedParent)
+								{
+									$parentChildInfo  = '';
+								}
+							}
+						}
+					}
+				}
+				else
+				{
+					$additional .= $addLink && $allow ? Text::_('COM_ASSOCIATIONS_EDIT_ASSOCIATION') : '';
+				}
 			}
+			// Get html parameters for not associated items
 			else
 			{
+				// Don't display any other children to the child item
+				if ($defaultAssocLang && ($itemLanguage != $defaultAssocLang)
+					&& ($langCode != $itemLanguage)
+					&& ($langCode != $defaultAssocLang))
+				{
+					continue;
+				}
+
 				$items[$langCode] = array();
 
 				$title      = Text::_('COM_ASSOCIATIONS_NO_ASSOCIATION');
 				$additional = $addLink ? Text::_('COM_ASSOCIATIONS_ADD_NEW_ASSOCIATION') : '';
-				$labelClass = 'badge-warning';
+				$labelClass = 'badge-secondary';
 				$target     = $langCode . ':0:add';
 				$allow      = $canCreate;
+
+				if ($defaultAssocLang)
+				{
+					if ($defaultAssocLang === $langCode)
+					{
+						$labelClass          .= ' parent-item';
+						$parentChildInfoSpace = $addLink ? '<br><br>' : '';
+						$parentChildInfo      = $parentChildInfoSpace . Text::_('JGLOBAL_ASSOCIATIONS_DEFAULT_ASSOC_LANG_ITEM');
+						$target               = '';
+					}
+					else
+					{
+						// Don't display not corresponding item
+						if ($assocState !== 'all' && $assocState !== 'not_associated')
+						{
+							unset($items[$langCode]);
+							continue;
+						}
+					}
+
+					// Change target, when there is no association with the default association language for the child item
+					if ($defaultAssocLang !== $itemLanguage)
+					{
+						$target = $defaultAssocLang . ':0:add';
+					}
+				}
 			}
 
 			// Generate item Html.
 			$options   = array(
 				'option'   => 'com_associations',
 				'view'     => 'association',
-				'layout'   => 'edit',
+				'layout'   => $update ? 'update' : 'edit',
 				'itemtype' => $extensionName . '.' . $typeName,
 				'task'     => 'association.edit',
-				'id'       => $itemId,
+				'id'       => $parentId ?? $itemId,
 				'target'   => $target,
 			);
 
@@ -321,11 +474,18 @@ public static function getAssociationHtmlList($extensionName, $typeName, $itemId
 			$text    = strtoupper($language->sef);
 
 			$tooltip = '<strong>' . htmlspecialchars($language->title, ENT_QUOTES, 'UTF-8') . '</strong><br>'
-				. htmlspecialchars($title, ENT_QUOTES, 'UTF-8') . '<br><br>' . $additional;
+				. htmlspecialchars($title, ENT_QUOTES, 'UTF-8') . '<br><br>' . $additional . $parentChildInfo;
 			$classes = 'badge ' . $labelClass;
 
 			$items[$langCode]['link'] = '<a href="' . $url . '" title="' . $language->title . '" class="' . $classes . '">' . $text . '</a>'
 				. '<div role="tooltip">' . $tooltip . '</div>';
+
+			// Reorder the array, so the parent gets to the first place
+			if ($langCode === $defaultAssocLang)
+			{
+				$items = array('parent' => $items[$langCode]) + $items;
+				unset($items[$langCode]);
+			}
 		}
 
 		return LayoutHelper::render('joomla.content.associations', $items);
diff --git a/administrator/components/com_associations/Helper/DefaultAssocLangHelper.php b/administrator/components/com_associations/Helper/DefaultAssocLangHelper.php
new file mode 100644
index 0000000000000..958ffcb217cb8
--- /dev/null
+++ b/administrator/components/com_associations/Helper/DefaultAssocLangHelper.php
@@ -0,0 +1,314 @@
+<?php
+/**
+ * @package     Joomla.Administrator
+ * @subpackage  com_associations
+ *
+ * @copyright   Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+namespace Joomla\Component\Associations\Administrator\Helper;
+
+use Joomla\CMS\Component\ComponentHelper;
+use Joomla\CMS\Factory;
+use Joomla\CMS\Helper\ContentHelper;
+use Joomla\CMS\Helper\ContentHistoryHelper;
+use Joomla\CMS\Language\Text;
+use Joomla\CMS\Router\Route;
+use Joomla\CMS\Table\Table;
+use Joomla\Database\ParameterType;
+
+defined('_JEXEC') or die;
+
+/**
+ * Associations component helper with default association language.
+ *
+ * @since  4.0
+ */
+class DefaultAssocLangHelper extends ContentHelper
+{
+	/**
+	 * Method to create a link for a child item that has no parent
+	 *
+	 * @param   string   $defaultAssocLang  The default association language
+	 * @param   integer  $itemId            The item id
+	 * @param   string   $itemType          The item type
+	 *
+	 * @return  string  the link for the not associated parent
+	 */
+	public static function addNotAssociatedParentLink($defaultAssocLang, $itemId, $itemType)
+	{
+		$db    = Factory::getDbo();
+		$query = $db->getQuery(true)
+			->select($db->quoteName(['title', 'sef']))
+			->from($db->quoteName('#__languages'))
+			->where($db->quoteName('lang_code') . ' = :lang_code')
+			->bind(':lang_code', $defaultAssocLang);
+		$db->setQuery($query);
+		$defaultAssocLangInfos = $db->loadAssoc();
+
+		$classes         = 'badge badge-secondary';
+		$parentChildInfo = '<br><br>' . Text::_('JGLOBAL_ASSOCIATIONS_DEFAULT_ASSOC_LANG_ITEM');
+		$text            = $defaultAssocLangInfos['sef'] ? strtoupper($defaultAssocLangInfos['sef']) : 'XX';
+		$title           = Text::_('JGLOBAL_ASSOCIATIONS_STATE_NOT_ASSOCIATED_DESC');
+		$url             = Route::_(self::getAssociationUrl($itemId, $defaultAssocLang, $itemType));
+
+		$tooltip = '<strong>' . htmlspecialchars($defaultAssocLangInfos['title'], ENT_QUOTES, 'UTF-8') . '</strong><br>'
+			. htmlspecialchars($title, ENT_QUOTES, 'UTF-8') . $parentChildInfo;
+
+		$link = '<a href="' . $url . '" title="' . $defaultAssocLangInfos['title'] . '" class="' . $classes . '">' . $text . '</a>'
+			. '<div role="tooltip" id="tip_no_parent">' . $tooltip . '</div>';
+
+		return $link;
+	}
+
+	/**
+	 * Method to get parent dates of each item of an association
+	 *
+	 * @param   array   $associations  the associations to be saved
+	 * @param   string  $context       the association context
+	 *
+	 * @return  array  association with parent dates
+	 */
+	public static function getParentDates($associations, $context)
+	{
+		$parentDates = [];
+		$db          = Factory::getDbo();
+
+		foreach ($associations as $langCode => $id)
+		{
+			if (is_array($id))
+			{
+				$id = $id['id'];
+			}
+
+			$query = $db->getQuery(true)
+				->select($db->quoteName(['parent_date', 'key']))
+				->from($db->quoteName('#__associations'))
+				->where(
+					[
+						$db->quoteName('id') . ' = :id',
+						$db->quoteName('context') . ' = :context'
+					]
+				)
+				->bind(':id', $id, ParameterType::INTEGER)
+				->bind(':context', $context);
+			$db->setQuery($query);
+			$parentDates[$id] = $db->loadRow();
+		}
+
+		return $parentDates;
+	}
+
+	/**
+	 * Method to get parent_id and parent_date for an association going to be saved.
+	 *
+	 * @param   integer  $id                Item id
+	 * @param   integer  $dataId            Item id of an item that is going to be saved
+	 * @param   integer  $parentId          Id of the associated parent
+	 * @param   string   $parentModified    The latest modified date of the parent
+	 * @param   array    $assocParentDates  Parents modified date of an associated item
+	 * @param   string   $old_key           The old association key to check if it is a new association
+	 *
+	 * @return  array    parent id and parent dates for an associated item
+	 */
+	public static function getParentValues($id, $dataId, $parentId, $parentModified, $assocParentDates, $old_key)
+	{
+		if ($parentId)
+		{
+			// For the parent
+			if ($parentId === $id)
+			{
+				$parentIdValue = 0;
+
+				// Set always the last modified date
+				$parentDateValue = $parentModified ?? 'NULL';
+			}
+
+			// For the children
+			else
+			{
+				$parentIdValue = $parentId;
+
+				// If modified date isn't set to the child item, set current modified date from parent OR if child is added from another association
+				$parentDateValue = (
+					empty($assocParentDates[$id][0])
+					|| ($assocParentDates[$id][1] !== $old_key)
+					|| ($assocParentDates[$parentId][1] !== $assocParentDates[$id][1])
+				)
+					? $parentModified
+					: $assocParentDates[$id][0];
+
+				if (!$old_key && ($dataId !== $id))
+				{
+					// Add modified date from parent to new associated item
+					$parentDateValue = $parentModified ?? 'NULL';
+				}
+			}
+		}
+		else
+		{
+			// Default values when there is no associated parent.
+			$parentIdValue   = -1;
+			$parentDateValue = 'NULL';
+		}
+
+		return [(int) $parentIdValue, $parentDateValue];
+	}
+
+	/**
+	 * Method to get the latest modified date of a parent
+	 *
+	 * @param   integer  $parentId   Id of the associated parent
+	 * @param   string   $tableName  The name of the table
+	 * @param   string   $typeAlias  Alias for the content type
+	 *
+	 * @return  string   The modified date of the parent
+	 */
+	public static function getParentModifiedDate($parentId, $tableName, $typeAlias)
+	{
+		// Check if the content version is enabled
+		$aliasParts         = explode('.', $typeAlias);
+		$saveHistory        = ComponentHelper::getParams($aliasParts[0])->get('save_history', 0);
+		$contentTypeTable   = Table::getInstance('ContentType');
+		$contentTypeTblName = $contentTypeTable->getTableName();
+		$typeId             = $contentTypeTable->getTypeId($typeAlias);
+
+		$db = Factory::getDbo();
+		$fieldMapsQuery = $db->getQuery(true)
+			->select($db->quoteName('field_mappings'))
+			->from($db->quoteName($contentTypeTblName))
+			->where($db->quoteName('type_id') . ' = :type_id')
+			->bind(':type_id', $typeId, ParameterType::INTEGER);
+		$db->setQuery($fieldMapsQuery);
+		$fieldMaps = $db->loadResult();
+
+		$modifiedColumn = json_decode($fieldMaps)->common->core_modified_time;
+
+		if ($parentId)
+		{
+			// If versions are enabled get the save_date of the parent from history table
+			if ($saveHistory)
+			{
+				$parentHistory = ContentHistoryHelper::getHistory($typeId, $parentId);
+
+				// Latest saved date of the parent
+				$parentModified = $parentHistory[0]->save_date;
+			}
+			else
+			{
+				$parentDateQuery = $db->getQuery(true)
+					->select($db->quoteName($modifiedColumn))
+					->from($db->quoteName($tableName))
+					->where($db->quoteName('id') . ' = :id')
+					->bind(':id', $parentId, ParameterType::INTEGER);
+				$db->setQuery($parentDateQuery);
+				$parentModified = $db->loadResult();
+			}
+		}
+
+		return $parentModified ?? '';
+	}
+
+	/**
+	 * Method to set class name and information about the association state or the parent.
+	 *
+	 * @param   integer  $itemId            Item id
+	 * @param   array    $items             The associated items for the item with the itemId
+	 * @param   integer  $key               The current key from $items that is currently going through the foreach loop
+	 * @param   array    $item              The current value from $items that is currently going through the foreach loop
+	 * @param   string   $defaultAssocLang  The default association language
+	 * @param   boolean  $isParent          If the item with $itemId is a parent
+	 * @param   integer  $parentId          Id of the associated parent
+	 * @param   array    $assocParentDates  Parent Dates of each associated item
+	 * @param   boolean  $saveHistory       If Versions are enabled or not
+	 *
+	 * @return  array  the className and parentInfo for the association state, the array $items back and boolean if item needs update.
+	 */
+	public static function setParentAndChildInfos($itemId, $items, $key, $item, $defaultAssocLang, $isParent, $parentId, $assocParentDates, $saveHistory)
+	{
+
+		$addClass   = 'badge-success';
+		$parentInfo = '';
+		$update     = false;
+
+		// Don't display other children if the current item is a child.
+		if (($key !== $itemId) && ($defaultAssocLang !== $item->lang_code) && !$isParent)
+		{
+			unset($items[$key]);
+		}
+
+		if ($key === $parentId)
+		{
+			$addClass   .= ' parent-item';
+			$parentInfo  = '<br><br>' . Text::_('JGLOBAL_ASSOCIATIONS_DEFAULT_ASSOC_LANG_ITEM');
+		}
+		else
+		{
+			// Get association state of child when a parent item exists
+			if ($parentId && (array_key_exists($key, $assocParentDates)) && (array_key_exists($parentId, $assocParentDates)))
+			{
+				$associatedModifiedParent = $assocParentDates[$key][0];
+				$lastModifiedParent       = $assocParentDates[$parentId][0];
+
+				if ($associatedModifiedParent < $lastModifiedParent)
+				{
+					$update     = true;
+					$addClass   = 'badge-warning';
+					$parentInfo = $saveHistory
+						? '<br><br>' . Text::_('JGLOBAL_ASSOCIATIONS_STATE_OUT_OF_DATE_DESC')
+						: '<br><br>' . Text::_('JGLOBAL_ASSOCIATIONS_STATE_MIGHT_BE_OUT_OF_DATE_DESC');
+				}
+				else
+				{
+					$addClass   = 'badge-success';
+					$parentInfo = '<br><br>' . Text::_('JGLOBAL_ASSOCIATIONS_STATE_UP_TO_DATE_DESC');
+				}
+			}
+		}
+
+		return [$addClass, $parentInfo, $items, $update];
+	}
+
+	/**
+	 * Method to get the association url for an item
+	 *
+	 * @param   integer  $itemId            The item id
+	 * @param   string   $defaultAssocLang  The default association language
+	 * @param   string   $itemType          The item type
+	 * @param   string   $itemLang          The current value from $items that is currently going through the foreach loop
+	 * @param   integer  $key               The current key from $items that is currently going through the foreach loop
+	 * @param   integer  $parentId          Id of the associated parent
+	 * @param   boolean  $needsUpdate       If the item needs an update or not
+	 *
+	 * @return string
+	 */
+	public static function getAssociationUrl($itemId, $defaultAssocLang, $itemType, $itemLang = '', $key = '', $parentId = '', $needsUpdate = false)
+	{
+		$target = '';
+
+		if (empty($parentId))
+		{
+			$target = $defaultAssocLang . ':0:add';
+		}
+		elseif ($key !== $parentId)
+		{
+			$target = $itemLang . ':' . $itemId . ':edit';
+		}
+
+		// Generate item Html.
+		$options   = array(
+			'option'   => 'com_associations',
+			'view'     => 'association',
+			'layout'   => $needsUpdate ? 'update' : 'edit',
+			'itemtype' => $itemType,
+			'task'     => 'association.edit',
+			'id'       => empty($parentId) ? $itemId : $parentId,
+			'target'   => $target,
+		);
+
+		$url = 'index.php?' . http_build_query($options);
+
+		return $url;
+	}
+}
diff --git a/administrator/components/com_associations/Model/AssociationModel.php b/administrator/components/com_associations/Model/AssociationModel.php
index 8ed1685a28658..881ed5b9cffe1 100644
--- a/administrator/components/com_associations/Model/AssociationModel.php
+++ b/administrator/components/com_associations/Model/AssociationModel.php
@@ -11,7 +11,9 @@
 
 defined('_JEXEC') or die;
 
+use Joomla\CMS\Factory;
 use Joomla\CMS\MVC\Model\ListModel;
+use Joomla\Database\ParameterType;
 
 /**
  * Methods supporting a list of article records.
@@ -37,4 +39,84 @@ public function getForm($data = array(), $loadData = true)
 
 		return !empty($form) ? $form : false;
 	}
+
+	/**
+	 * Method to get the history version ids of a parent.
+	 *
+	 * @param   integer  $parentId       Id of the parent
+	 * @param   integer  $targetId       Id of a child
+	 * @param   string   $extensionName  The extension name with com_
+	 * @param   string   $typeName       The item type
+	 * @param   integer  $typeId         the content type id
+	 *
+	 * @return  array    Array containing two version history ids
+	 */
+	public function getParentCompareValues($parentId, $targetId, $extensionName, $typeName, $typeId)
+	{
+
+		$context = ($typeName === 'category')
+			? 'com_categories.item'
+			: $extensionName . '.item';
+
+		$db = Factory::getDbo();
+		$parentQuery = $db->getQuery(true)
+			->select($db->quoteName('parent_date'))
+			->from($db->quoteName('#__associations'))
+			->where(
+				[
+					$db->quoteName('id') . ' = :id',
+					$db->quoteName('context') . ' = :context'
+				]
+			)
+			->bind(':id', $parentId, ParameterType::INTEGER)
+			->bind(':context', $context);
+		$latestParentDate = $db->setQuery($parentQuery)->loadResult();
+
+		$latestVersionQuery = $db->getQuery(true)
+			->select($db->quoteName('version_id'))
+			->from($db->quoteName('#__ucm_history'))
+			->where(
+				[
+					$db->quoteName('ucm_item_id') . ' = :ucm_item_id',
+					$db->quoteName('ucm_type_id') . ' = :ucm_type_id',
+					$db->quoteName('save_date') . ' = :save_date'
+				]
+			)
+			->bind(':ucm_item_id', $parentId, ParameterType::INTEGER)
+			->bind(':ucm_type_id', $typeId, ParameterType::INTEGER)
+			->bind(':save_date', $latestParentDate);
+		$latestVersionId = $db->setQuery($latestVersionQuery)->loadResult();
+
+		$childQuery = $db->getQuery(true)
+			->select($db->quoteName('parent_date'))
+			->from($db->quoteName('#__associations'))
+			->where(
+				[
+					$db->quoteName('id') . ' = :id',
+					$db->quoteName('parent_id') . ' = :parent_id',
+					$db->quoteName('context') . ' = :context'
+				]
+			)
+			->bind(':id', $targetId, ParameterType::INTEGER)
+			->bind(':parent_id', $parentId, ParameterType::INTEGER)
+			->bind(':context', $context);
+		$childParentDate = $db->setQuery($childQuery)->loadResult();
+
+		$olderVersionQuery = $db->getQuery(true)
+			->select($db->quoteName('version_id'))
+			->from($db->quoteName('#__ucm_history'))
+			->where(
+				[
+					$db->quoteName('ucm_item_id') . ' = :ucm_item_id',
+					$db->quoteName('ucm_type_id') . ' = :ucm_type_id',
+					$db->quoteName('save_date') . ' = :save_date'
+				]
+			)
+			->bind(':ucm_item_id', $parentId, ParameterType::INTEGER)
+			->bind(':ucm_type_id', $typeId, ParameterType::INTEGER)
+			->bind(':save_date', $childParentDate);
+		$olderVersionId = $db->setQuery($olderVersionQuery)->loadResult();
+
+		return [$latestVersionId, $olderVersionId];
+	}
 }
diff --git a/administrator/components/com_associations/Model/AssociationsModel.php b/administrator/components/com_associations/Model/AssociationsModel.php
index d4e0d2379fb5d..31a3c3a8cdbb5 100644
--- a/administrator/components/com_associations/Model/AssociationsModel.php
+++ b/administrator/components/com_associations/Model/AssociationsModel.php
@@ -11,13 +11,17 @@
 
 defined('_JEXEC') or die;
 
+use Joomla\CMS\Component\ComponentHelper;
 use Joomla\CMS\Factory;
+use Joomla\CMS\Language\Associations;
+use Joomla\CMS\Language\LanguageHelper;
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\MVC\Factory\MVCFactoryInterface;
 use Joomla\CMS\MVC\Model\ListModel;
 use Joomla\CMS\Table\Table;
 use Joomla\Component\Associations\Administrator\Helper\AssociationsHelper;
 use Joomla\Database\Exception\ExecutionFailureException;
+use Joomla\Database\ParameterType;
 
 /**
  * Methods supporting a list of article records.
@@ -45,6 +49,7 @@ public function __construct($config = array(), MVCFactoryInterface $factory = nu
 				'ordering',
 				'itemtype',
 				'language',
+				'assocstate',
 				'association',
 				'menutype',
 				'menutype_title',
@@ -79,6 +84,13 @@ protected function populateState($ordering = 'ordering', $direction = 'asc')
 		$forcedLanguage = $app->input->get('forcedLanguage', '', 'cmd');
 		$forcedItemType = $app->input->get('forcedItemType', '', 'string');
 
+		// Set language select box to default site language or if set to, to the default association language as default.
+		$defaultAssocLang = Associations::getDefaultAssocLang();
+		$langParam        = ComponentHelper::getParams('com_languages');
+
+		$defaultLanguage  = empty($defaultAssocLang) ? $langParam->get('site') : $defaultAssocLang;
+		$defaultItemType  = 'com_content.article';
+
 		// Adjust the context to support modal layouts.
 		if ($layout = $app->input->get('layout'))
 		{
@@ -97,9 +109,9 @@ protected function populateState($ordering = 'ordering', $direction = 'asc')
 			$this->context .= '.' . $forcedItemType;
 		}
 
-		$this->setState('itemtype', $this->getUserStateFromRequest($this->context . '.itemtype', 'itemtype', '', 'string'));
-		$this->setState('language', $this->getUserStateFromRequest($this->context . '.language', 'language', '', 'string'));
-
+		$this->setState('itemtype', $this->getUserStateFromRequest($this->context . '.itemtype', 'itemtype', $defaultItemType, 'string'));
+		$this->setState('language', $this->getUserStateFromRequest($this->context . '.language', 'language', $defaultLanguage, 'string'));
+		$this->setState('assocstate', $this->getUserStateFromRequest($this->context . '.assocstate', 'assocstate', 'all', 'string'));
 		$this->setState('filter.search', $this->getUserStateFromRequest($this->context . '.filter.search', 'filter_search', '', 'string'));
 		$this->setState('filter.state', $this->getUserStateFromRequest($this->context . '.filter.state', 'filter_state', '', 'cmd'));
 		$this->setState('filter.category_id', $this->getUserStateFromRequest($this->context . '.filter.category_id', 'filter_category_id', '', 'cmd'));
@@ -141,6 +153,7 @@ protected function getStoreId($id = '')
 		// Compile the store id.
 		$id .= ':' . $this->getState('itemtype');
 		$id .= ':' . $this->getState('language');
+		$id .= ':' . $this->getState('assocstate');
 		$id .= ':' . $this->getState('filter.search');
 		$id .= ':' . $this->getState('filter.state');
 		$id .= ':' . $this->getState('filter.category_id');
@@ -166,6 +179,7 @@ protected function getListQuery()
 
 		$extension = AssociationsHelper::getSupportedExtension($extensionName);
 		$types     = $extension->get('types');
+		$assocContextName = ($typeName === 'category') ? 'com_categories.item' : $extensionName . '.item';
 
 		if (array_key_exists($typeName, $types))
 		{
@@ -235,12 +249,12 @@ protected function getListQuery()
 
 		// Join over the associations.
 		$query->select('COUNT(' . $db->quoteName('asso2.id') . ') > 1 AS ' . $db->quoteName('association'))
-			->join(
-				'LEFT',
+			->leftJoin(
 				$db->quoteName('#__associations', 'asso') . ' ON ' . $db->quoteName('asso.id') . ' = ' . $db->quoteName($fields['id'])
-				. ' AND ' . $db->quoteName('asso.context') . ' = ' . $db->quote($extensionName . '.item')
+				. ' AND ' . $db->quoteName('asso.context') . ' = :context'
 			)
-			->join('LEFT', $db->quoteName('#__associations', 'asso2') . ' ON ' . $db->quoteName('asso2.key') . ' = ' . $db->quoteName('asso.key'));
+			->leftJoin($db->quoteName('#__associations', 'asso2') . ' ON ' . $db->quoteName('asso2.key') . ' = ' . $db->quoteName('asso.key'))
+			->bind(':context', $assocContextName);
 
 		// Prepare the group by clause.
 		$groupby = array(
@@ -432,6 +446,60 @@ protected function getListQuery()
 			}
 		}
 
+		// Filter by association state
+		$assocStateField = $this->state->get('assocstate');
+
+		if ($assocStateField !== 'all')
+		{
+			// Not associated
+			if ($assocStateField === 'not_associated')
+			{
+				$countContentLanguages = count(LanguageHelper::getContentLanguages(array(0, 1)));
+
+				// Get all keys where not all languages are associated.
+				$assocQuery = $db->getQuery(true)
+					->select($db->quoteName('key'))
+					->from($db->quoteName('#__associations'))
+					->group($db->quoteName('key'))
+					->having('COUNT(*) < :count');
+
+				// Join over associations where id does not exist
+				$query->where('((' . $db->quoteName('asso.id') . ' IS NULL )'
+					// Or if we are on the child language and there is no parent
+					. ' OR ( ' . $db->quoteName('asso2.parent_id') . ' = -1)'
+					// Or a child of the parent does not exist.
+					. ' OR ( ' . $db->quoteName('asso.key') . '  IN (' . $assocQuery . ') 
+						AND ' . $db->quoteName('asso.parent_id') . ' = 0)'
+					. ')'
+				)
+					->bind(':count', $countContentLanguages, ParameterType::INTEGER);
+			}
+
+			// Out-of-date
+			if ($assocStateField === 'out_of_date')
+			{
+				// If we are on the parent language and we check the state of the children
+				$query->where('((' . $db->quoteName('asso2.parent_id') . ' = ' . $db->quoteName('asso.id')
+					. ' AND ' . $db->quoteName('asso2.parent_date') . ' < ' . $db->quoteName('asso.parent_date') . ')'
+					//  Or we are on the child language and we check its state comparing to its parent.
+					. ' OR (' . $db->quoteName('asso.parent_date') . ' < ' . $db->quoteName('asso2.parent_date')
+					. ' AND ' . $db->quoteName('asso2.id') . ' = ' . $db->quoteName('asso.parent_id') . '))'
+				);
+			}
+
+			// Up-to-date
+			if ($assocStateField === 'up_to_date')
+			{
+				// If we are on the parent language and we check the state of the children
+				$query->where('((' . $db->quoteName('asso2.parent_id') . ' = ' . $db->quoteName('asso.id')
+					. ' AND ' . $db->quoteName('asso2.parent_date') . ' = ' . $db->quoteName('asso.parent_date') . ')'
+					// Or we are on the child language and we check its state comparing to its parent.
+					. ' OR (' . $db->quoteName('asso.parent_date') . ' = ' . $db->quoteName('asso2.parent_date')
+					. ' AND ' . $db->quoteName('asso2.id') . ' = ' . $db->quoteName('asso.parent_id') . '))'
+				);
+			}
+		}
+
 		// Add the group by clause
 		$query->group($db->quoteName($groupby));
 
@@ -463,7 +531,29 @@ public function purge($context = '', $key = '')
 		// Filter by associations context.
 		if ($context)
 		{
-			$query->where($db->quoteName('context') . ' = ' . $db->quote($context));
+			list($extensionName, $typeName) = explode('.', $context, 2);
+
+			// The associations of the type category may only be deleted with the appropriate context,
+			// therefore with the appropriate extension. Not all categories.
+			if ($typeName === 'category')
+			{
+				// Subquery: Search for category-items with the given context
+				$subQuery = $db->getQuery(true)
+					->select($db->quoteName('id'))
+					->from($db->quoteName('#__categories'))
+					->where($db->quoteName('extension') . ' = :extension')
+					->bind(':extension', $extensionName);
+				$idResults = $db->setQuery($subQuery)->loadColumn();
+
+				// Delete associations of categories with the given context by comparing id of both tables
+				$query->whereIn($db->quoteName('id'), $idResults, ParameterType::INTEGER)
+					->where($db->quoteName('context') . ' = :context')
+					->bind(':context', $context = 'com_categories.item');
+			}
+			else
+			{
+				$query->where($db->quoteName('context') . ' = ' . $db->quote($extensionName . '.item'));
+			}
 		}
 
 		// Filter by key.
diff --git a/administrator/components/com_associations/Model/DefaultAssocLangModel.php b/administrator/components/com_associations/Model/DefaultAssocLangModel.php
new file mode 100644
index 0000000000000..5fe957cf57e45
--- /dev/null
+++ b/administrator/components/com_associations/Model/DefaultAssocLangModel.php
@@ -0,0 +1,88 @@
+<?php
+/**
+ * @package     Joomla.Administrator
+ * @subpackage  com_associations
+ *
+ * @copyright   Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+namespace Joomla\Component\Associations\Administrator\Model;
+
+defined('_JEXEC') or die;
+
+use Joomla\CMS\Factory;
+use Joomla\CMS\MVC\Model\BaseModel;
+use Joomla\Database\ParameterType;
+
+/**
+ * Methods supporting a list of article records.
+ *
+ * @since  4.0
+ */
+class DefaultAssocLangModel extends BaseModel
+{
+
+	/**
+	 * Update the childs modified date of the parent from #__associations table.
+	 *
+	 * @param   integer  $childId   The id of the item that gets updated
+	 * @param   integer  $parentId  The associated parent of the child item
+	 * @param   string   $itemtype  The component item type
+	 *
+	 * @return  boolean  True on success.
+	 *
+	 * @since  4.0
+	 */
+	public function update($childId, $parentId, $itemtype)
+	{
+		list($extensionName, $typeName) = explode('.', $itemtype, 2);
+
+		$context = ($typeName === 'category')
+			? 'com_categories.item'
+			: $extensionName . '.item';
+		$db      = Factory::getDbo();
+
+		$subQuery = $db->getQuery(true)
+			->select($db->quoteName('parent_date'))
+			->from($db->quoteName('#__associations'))
+			->where(
+				[
+					$db->quoteName('id') . ' = :id',
+					$db->quoteName('parent_id') . ' = ' . $db->quote(0),
+					$db->quoteName('context') . ' = :context'
+				]
+			)
+			->bind(':id', $parentId, ParameterType::INTEGER)
+			->bind(':context', $context);
+		$parentModified = $db->setQuery($subQuery)->loadResult();
+		$parentModifiedSql = Factory::getDate($parentModified)->toSql();
+
+		$query = $db->getQuery(true)
+			->update($db->quoteName('#__associations'))
+			->set($db->quoteName('parent_date') . ' = :parent_date')
+			->where(
+				[
+					$db->quoteName('id') . ' = :id',
+					$db->quoteName('parent_id') . ' = :parent_id',
+					$db->quoteName('context') . ' = :context'
+				]
+			)
+			->bind(':parent_date', $parentModifiedSql)
+			->bind(':id', $childId, ParameterType::INTEGER)
+			->bind(':parent_id', $parentId, ParameterType::INTEGER)
+			->bind(':context', $context);
+		$db->setQuery($query);
+
+		try
+		{
+			$db->execute();
+		}
+		catch (ExecutionFailureException $e)
+		{
+			return false;
+		}
+
+		return true;
+	}
+}
diff --git a/administrator/components/com_associations/View/Association/HtmlView.php b/administrator/components/com_associations/View/Association/HtmlView.php
index f1a412e22553d..29ba8360c1be8 100644
--- a/administrator/components/com_associations/View/Association/HtmlView.php
+++ b/administrator/components/com_associations/View/Association/HtmlView.php
@@ -11,10 +11,12 @@
 
 defined('_JEXEC') or die;
 
+use Joomla\CMS\Component\ComponentHelper;
 use Joomla\CMS\Factory;
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\MVC\View\HtmlView as BaseHtmlView;
 use Joomla\CMS\Router\Route;
+use Joomla\CMS\Table\Table;
 use Joomla\CMS\Toolbar\Toolbar;
 use Joomla\CMS\Toolbar\ToolbarHelper;
 use Joomla\Component\Associations\Administrator\Helper\AssociationsHelper;
@@ -169,6 +171,27 @@ public function display($tpl = null)
 			$this->targetTitle      = AssociationsHelper::getTypeFieldName($extensionName, $typeName, 'title');
 			$task                   = $typeName . '.' . $this->targetAction;
 
+			// The update layout can only be set when a default association language is used.
+			// Get version ids of the parent, when versions are enabled.
+			if ($this->getLayout() === 'update')
+			{
+				$saveHistory = ComponentHelper::getParams($extensionName)->get('save_history', 0);
+
+				if ($saveHistory)
+				{
+					$typeAlias        = $typeName === 'category' ? $extensionName . '.' . $typeName : $reference['typeAlias'];
+					$model            = $this->getModel();
+					$typeId           = Table::getInstance('ContentType')->getTypeId($typeAlias);
+					$parentVersionIds = $model->getParentCompareValues($referenceId, $this->targetId, $extensionName, $typeName, $typeId);
+
+					if ($parentVersionIds[0] !== null && $parentVersionIds[1] !== null)
+					{
+						$this->referenceVersionIdNew = $parentVersionIds[0];
+						$this->referenceVersionIdOld = $parentVersionIds[1];
+					}
+				}
+			}
+
 			/*
 			 * Let's put the target src into a variable to use in the javascript code
 			 *  to avoid race conditions when the reference iframe loads.
@@ -207,23 +230,43 @@ protected function addToolbar()
 
 		ToolbarHelper::title(Text::sprintf('COM_ASSOCIATIONS_TITLE_EDIT', Text::_($this->extensionName), Text::_($languageKey)), 'language assoc');
 
-		$bar = Toolbar::getInstance('toolbar');
-
-		$bar->appendButton(
-			'Custom', '<button onclick="Joomla.submitbutton(\'reference\')" '
-			. 'class="btn btn-sm btn-success"><span class="icon-apply" aria-hidden="true"></span>'
-			. Text::_('COM_ASSOCIATIONS_SAVE_REFERENCE') . '</button>', 'reference'
-		);
+		$toolbar = Toolbar::getInstance('toolbar');
 
-		$bar->appendButton(
-			'Custom', '<button onclick="Joomla.submitbutton(\'target\')" '
-			. 'class="btn btn-sm btn-success"><span class="icon-apply" aria-hidden="true"></span>'
-			. Text::_('COM_ASSOCIATIONS_SAVE_TARGET') . '</button>', 'target'
-		);
+		// The update layout can only be set when a default association language is used.
+		if ($this->getLayout() === 'update')
+		{
+			// In the update view we can just save the target
+			$toolbar->appendButton(
+				'Custom', '<button onclick="Joomla.submitbutton(\'target\')" '
+				. 'class="btn btn-sm btn-success"><span class="icon-apply" aria-hidden="true"></span>'
+				. Text::_('COM_ASSOCIATIONS_SAVE_AND_UPDATE_TARGET') . '</button>', 'target'
+			);
 
-		if ($this->typeName === 'category' || $this->extensionName === 'com_menus' || $this->save2copy === true)
+			// And when saving the target this button gets activated via js to update the parent's date for the child
+			$toolbar->appendButton(
+				'Custom', '<button class="btn btn-sm btn-success hidden" id="updateChild" 
+					onclick="Joomla.submitbutton(\'defaultAssocLang.update\')"></button>', 'target'
+			);
+		}
+		else
 		{
-			ToolbarHelper::custom('copy', 'copy.png', '', 'COM_ASSOCIATIONS_COPY_REFERENCE', false);
+			$toolbar->appendButton(
+				'Custom', '<button onclick="Joomla.submitbutton(\'reference\')" '
+				. 'class="btn btn-sm btn-success"><span class="icon-apply" aria-hidden="true"></span>'
+				. Text::_('COM_ASSOCIATIONS_SAVE_REFERENCE') . '</button>',
+				'reference'
+			);
+
+			$toolbar->appendButton(
+				'Custom', '<button onclick="Joomla.submitbutton(\'target\')" '
+				. 'class="btn btn-sm btn-success"><span class="icon-apply" aria-hidden="true"></span>'
+				. Text::_('COM_ASSOCIATIONS_SAVE_TARGET') . '</button>', 'target'
+			);
+
+			if ($this->typeName === 'category' || $this->extensionName === 'com_menus' || $this->save2copy === true)
+			{
+				ToolbarHelper::custom('copy', 'copy.png', '', 'COM_ASSOCIATIONS_COPY_REFERENCE', false);
+			}
 		}
 
 		ToolbarHelper::cancel('association.cancel', 'JTOOLBAR_CLOSE');
diff --git a/administrator/components/com_associations/View/Associations/HtmlView.php b/administrator/components/com_associations/View/Associations/HtmlView.php
index b82befbf90488..dd56bb0635d07 100644
--- a/administrator/components/com_associations/View/Associations/HtmlView.php
+++ b/administrator/components/com_associations/View/Associations/HtmlView.php
@@ -16,6 +16,7 @@
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\MVC\View\HtmlView as BaseHtmlView;
 use Joomla\CMS\Router\Route;
+use Joomla\CMS\Toolbar\Toolbar;
 use Joomla\CMS\Toolbar\ToolbarHelper;
 use Joomla\Component\Associations\Administrator\Helper\AssociationsHelper;
 
@@ -77,6 +78,22 @@ public function display($tpl = null)
 		$this->filterForm    = $this->get('FilterForm');
 		$this->activeFilters = $this->get('ActiveFilters');
 
+		// Get default values and set these to selected to the select boxes
+		if ($this->state->get('itemtype'))
+		{
+			$this->filterForm->setValue('itemtype', null, $this->state->get('itemtype'));
+		}
+
+		if ($this->state->get('language'))
+		{
+			$this->filterForm->setValue('language', null, $this->state->get('language'));
+		}
+
+		if ($this->state->get('assocstate'))
+		{
+			$this->filterForm->setValue('assocstate', null, $this->state->get('assocstate'));
+		}
+
 		if (!Associations::isEnabled())
 		{
 			$link = Route::_('index.php?option=com_plugins&task=plugin.edit&extension_id=' . AssociationsHelper::getLanguagefilterPluginId());
@@ -132,6 +149,15 @@ public function display($tpl = null)
 				// This selectors doesn't have to activate the filter bar.
 				unset($this->activeFilters['itemtype']);
 				unset($this->activeFilters['language']);
+				unset($this->activeFilters['assocstate']);
+
+				// Remove association state filter depending on default association language
+				$defaultAssocLang = Associations::getDefaultAssocLang();
+
+				if (!$defaultAssocLang)
+				{
+					$this->filterForm->removeField('assocstate', 'filter');
+				}
 
 				// Remove filters options depending on selected type.
 				if (empty($support['state']))
@@ -213,6 +239,7 @@ public function display($tpl = null)
 	protected function addToolbar()
 	{
 		$user = Factory::getUser();
+		$toolbar = Toolbar::getInstance('toolbar');
 
 		if (isset($this->typeName) && isset($this->extensionName))
 		{
@@ -239,12 +266,15 @@ protected function addToolbar()
 
 		if ($user->authorise('core.admin', 'com_associations') || $user->authorise('core.options', 'com_associations'))
 		{
-			if (!isset($this->typeName))
-			{
-				ToolbarHelper::custom('associations.purge', 'purge', 'purge', 'COM_ASSOCIATIONS_PURGE', false, false);
-				ToolbarHelper::custom('associations.clean', 'refresh', 'refresh', 'COM_ASSOCIATIONS_DELETE_ORPHANS', false, false);
-			}
-
+			$toolbar->confirmButton('purge')
+				->text('COM_ASSOCIATIONS_PURGE')
+				->message(
+					(isset($this->extensionName) && isset($languageKey))
+						? Text::plural('COM_ASSOCIATIONS_PURGE_CONFIRM_PROMPT', (Text::_($this->extensionName) . ' > ' . Text::_($languageKey)))
+						: Text::_('COM_ASSOCIATIONS_PURGE_CONFIRM_PROMPT')
+				)
+				->task('associations.purge');
+			ToolbarHelper::custom('associations.clean', 'refresh', 'refresh', 'COM_ASSOCIATIONS_DELETE_ORPHANS', false, false);
 			ToolbarHelper::preferences('com_associations');
 		}
 
diff --git a/administrator/components/com_associations/forms/filter_associations.xml b/administrator/components/com_associations/forms/filter_associations.xml
index 6177a48df1c41..f094d10073c21 100644
--- a/administrator/components/com_associations/forms/filter_associations.xml
+++ b/administrator/components/com_associations/forms/filter_associations.xml
@@ -5,14 +5,14 @@
 		type="itemtype"
 		label="COM_ASSOCIATIONS_FILTER_SELECT_ITEM"
 		filtermode="selector"
-		onchange="Joomla.resetFilters(this)"
+		onchange="this.form.submit();"
 		>
 		<option value="">COM_ASSOCIATIONS_FILTER_SELECT_ITEM_TYPE</option>
 	</field>
 
 	<field
 		name="language"
-		type="contentlanguage"
+		type="contentdefaultassoclang"
 		label="COM_ASSOCIATIONS_FILTER_SELECT_LANGUAGE"
 		filtermode="selector"
 		onchange="this.form.submit();"
@@ -20,6 +20,19 @@
 		<option value="">JOPTION_SELECT_LANGUAGE</option>
 	</field>
 
+	<field
+		name="assocstate"
+		type="list"
+		label="COM_ASSOCIATIONS_FILTER_SELECT_ASSOCIATION_STATE"
+		filtermode="selector"
+		onchange="this.form.submit();"
+		>
+		<option value="all">COM_ASSOCIATIONS_FILTER_ASSOCIATION_STATE</option>
+		<option value="up_to_date">COM_ASSOCIATIONS_STATE_UP_TO_DATE</option>
+		<option value="out_of_date">COM_ASSOCIATIONS_STATE_OUT_OF_DATE</option>
+		<option value="not_associated">COM_ASSOCIATIONS_STATE_NOT_ASSOCIATED</option>
+	</field>
+
 	<fields name="filter">
 		<field
 			name="search"
diff --git a/administrator/components/com_associations/layouts/joomla/searchtools/default.php b/administrator/components/com_associations/layouts/joomla/searchtools/default.php
index b18582467c8a9..34e7d59ca30c4 100644
--- a/administrator/components/com_associations/layouts/joomla/searchtools/default.php
+++ b/administrator/components/com_associations/layouts/joomla/searchtools/default.php
@@ -11,6 +11,7 @@
 
 use Joomla\CMS\Factory;
 use Joomla\CMS\HTML\HTMLHelper;
+use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\Layout\LayoutHelper;
 
@@ -77,6 +78,7 @@
 
 // Merge custom options in the options array.
 $data['options'] = array_merge($customOptions, $data['options']);
+$defaultAssocLang = Associations::getDefaultAssocLang();
 
 // Add class to hide the active filters if needed.
 $filtersActiveClass = $hideActiveFilters ? '' : ' js-stools-container-filters-visible';
@@ -98,13 +100,28 @@
 	<?php endif; ?>
 	<?php if ($app->input->get('forcedLanguage', '', 'cmd') == '') : ?>
 		<?php $languageField = $data['view']->filterForm->getField('language'); ?>
-		<div class="js-stools-container-selector">
+		<?php if ($defaultAssocLang) : ?>
+			<div class="js-stools-container-selector-second">
+		<?php else : ?>
+			<div class="js-stools-container-selector">
+		<?php endif; ?>
 			<div class="js-stools-field-selector js-stools-language">
 				<div class="sr-only"><?php echo $languageField->label; ?></div>
 				<?php echo $languageField->input; ?>
 			</div>
 		</div>
 	<?php endif; ?>
+	<?php if ($defaultAssocLang) : ?>
+		<?php $assocStateField = $data['view']->filterForm->getField('assocstate'); ?>
+			<div class="js-stools-container-selector">
+				<div class="js-stools-field-selector js-stools-assocstate">
+					<label for="<?php echo $assocStateField->id; ?>" class="sr-only">
+						<?php echo Text::_('COM_ASSOCIATIONS_FILTER_SELECT_ASSOCIATION_STATE'); ?>
+					</label>
+					<?php echo $assocStateField->input; ?>
+				</div>
+			</div>
+	<?php endif; ?>
 	<?php if ($data['options']['showSelector']) : ?>
 	<div class="js-stools-container-selector">
 		<?php echo LayoutHelper::render('joomla.searchtools.default.selector', $data); ?>
diff --git a/administrator/components/com_associations/tmpl/association/update.php b/administrator/components/com_associations/tmpl/association/update.php
new file mode 100644
index 0000000000000..4141d64874913
--- /dev/null
+++ b/administrator/components/com_associations/tmpl/association/update.php
@@ -0,0 +1,74 @@
+<?php
+/**
+ * @package     Joomla.Administrator
+ * @subpackage  com_associations
+ *
+ * @copyright   Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+defined('_JEXEC') or die;
+
+use Joomla\CMS\HTML\HTMLHelper;
+use Joomla\CMS\Language\Text;
+use Joomla\CMS\Router\Route;
+use Joomla\CMS\Session\Session;
+
+HTMLHelper::_('behavior.formvalidator');
+HTMLHelper::_('behavior.keepalive');
+HTMLHelper::_('jquery.framework');
+
+HTMLHelper::_('script', 'com_associations/sidebysideupdate.js', ['version' => 'auto', 'relative' => true]);
+HTMLHelper::_('stylesheet', 'com_associations/sidebyside.css', ['version' => 'auto', 'relative' => true]);
+
+$options = array(
+	'layout'   => $this->app->input->get('layout', '', 'string'),
+	'itemtype' => $this->itemtype,
+	'id'       => $this->referenceId,
+	'targetId'   => $this->targetId
+);
+?>
+<form action="<?php echo Route::_('index.php?option=com_associations&view=association&' . http_build_query($options)); ?>" method="post" name="adminForm" id="adminForm" data-associatedview="<?php echo $this->typeName; ?>">
+	<div class="sidebyside">
+		<div class="outer-panel" id="left-panel">
+			<div class="inner-panel">
+				<?php if (isset($this->referenceVersionIdNew)) : ?>
+					<h3><?php echo Text::_('COM_ASSOCIATIONS_REFERENCE_ITEM_COMPARE_VIEW'); ?></h3>
+					<iframe id="reference-association" name="reference-association" title="reference-association"
+						src="<?php echo Route::_('index.php?option=com_contenthistory&view=compare&layout=compareassocparent&tmpl=component&' . Session::getFormToken() . '=1&id1=' . $this->referenceVersionIdNew . '&id2=' . $this->referenceVersionIdOld); ?>"
+						height="400" width="400" >
+					</iframe>
+				<?php else : ?>
+					<h3><?php echo Text::_('COM_ASSOCIATIONS_REFERENCE_ITEM'); ?></h3>
+					<iframe id="reference-association" name="reference-association" title="reference-association"
+						src="<?php echo Route::_($this->editUri . '&task=' . $this->typeName . '.edit&id=' . (int) $this->referenceId); ?>"
+						height="400" width="400"
+						data-action="edit"
+						data-item="<?php echo $this->typeName; ?>"
+						data-id="<?php echo $this->referenceId; ?>"
+						data-title="<?php echo $this->referenceTitle; ?>"
+						data-language="<?php echo $this->referenceLanguage; ?>"
+						data-editurl="<?php echo Route::_($this->editUri); ?>">
+					</iframe>
+				<?php endif; ?>
+			</div>
+		</div>
+		<div class="outer-panel" id="right-panel">
+			<div class="inner-panel">
+					<h3 class="target-text"><?php echo Text::_('COM_ASSOCIATIONS_ASSOCIATED_ITEM'); ?></h3>
+				<iframe id="target-association" name="target-association" title="target-association"
+						src="<?php echo Route::_($this->editUri . '&task=' . $this->typeName . '.edit&id=' . (int) $this->targetId); ?>"
+				        height="400" width="400"
+				        data-action="<?php echo $this->targetAction; ?>"
+				        data-item="<?php echo $this->typeName; ?>"
+				        data-id="<?php echo $this->targetId; ?>"
+				        data-title="<?php echo $this->targetTitle; ?>"
+				        data-language="<?php echo $this->targetLanguage; ?>"
+				        data-editurl="<?php echo Route::_($this->editUri); ?>">
+				</iframe>
+			</div>
+		</div>
+	</div>
+	<input type="hidden" name="task" value="">
+	<?php echo HTMLHelper::_('form.token'); ?>
+</form>
diff --git a/administrator/components/com_associations/tmpl/associations/default.php b/administrator/components/com_associations/tmpl/associations/default.php
index 12696b9bbcc55..b97bd91f6bbc4 100644
--- a/administrator/components/com_associations/tmpl/associations/default.php
+++ b/administrator/components/com_associations/tmpl/associations/default.php
@@ -11,6 +11,7 @@
 
 use Joomla\CMS\Factory;
 use Joomla\CMS\HTML\HTMLHelper;
+use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\Layout\LayoutHelper;
 use Joomla\CMS\Router\Route;
@@ -21,6 +22,8 @@
 $listOrder        = $this->escape($this->state->get('list.ordering'));
 $listDirn         = $this->escape($this->state->get('list.direction'));
 $canManageCheckin = Factory::getUser()->authorise('core.manage', 'com_checkin');
+$defaultAssocLang = Associations::getDefaultAssocLang();
+$assocState       = $this->escape($this->state->get('assocstate'));
 
 $iconStates = array(
 	-2 => 'icon-trash',
@@ -29,8 +32,6 @@
 	2  => 'icon-archive',
 );
 
-Text::script('COM_ASSOCIATIONS_PURGE_CONFIRM_PROMPT', true);
-HTMLHelper::_('script', 'com_associations/admin-associations-default.min.js', ['version' => 'auto', 'relative' => true]);
 ?>
 <form action="<?php echo Route::_('index.php?option=com_associations&view=associations'); ?>" method="post" name="adminForm" id="adminForm">
 	<div class="row">
@@ -60,12 +61,18 @@
 								<th scope="col" style="width:15%">
 									<?php echo Text::_('JGRID_HEADING_LANGUAGE'); ?>
 								</th>
-								<th scope="col" style="width:5%">
-									<?php echo Text::_('COM_ASSOCIATIONS_HEADING_ASSOCIATION'); ?>
-								</th>
-								<th scope="col" style="width:15%">
-									<?php echo Text::_('COM_ASSOCIATIONS_HEADING_NO_ASSOCIATION'); ?>
-								</th>
+								<?php if ($defaultAssocLang) : ?>
+									<th scope="col" style="width:15%" class="text-center">
+										<?php echo Text::_('COM_ASSOCIATIONS_HEADING_ASSOCIATION'); ?>
+									</th>
+								<?php else : ?>
+									<th scope="col" style="width:5%">
+										<?php echo Text::_('COM_ASSOCIATIONS_HEADING_ASSOCIATION'); ?>
+									</th>
+									<th scope="col" style="width:15%">
+										<?php echo Text::_('COM_ASSOCIATIONS_HEADING_NO_ASSOCIATION'); ?>
+									</th>
+								<?php endif; ?>
 								<?php if (!empty($this->typeFields['menutype'])) : ?>
 									<th scope="col" style="width:10%">
 										<?php echo HTMLHelper::_('searchtools.sort', 'COM_ASSOCIATIONS_HEADING_MENUTYPE', 'menutype_title', $listDirn, $listOrder); ?>
@@ -123,12 +130,18 @@
 								<td class="small">
 									<?php echo LayoutHelper::render('joomla.content.language', $item); ?>
 								</td>
-								<td>
-									<?php echo AssociationsHelper::getAssociationHtmlList($this->extensionName, $this->typeName, (int) $item->id, $item->language, !$isCheckout, false); ?>
-								</td>
-								<td>
-									<?php echo AssociationsHelper::getAssociationHtmlList($this->extensionName, $this->typeName, (int) $item->id, $item->language, !$isCheckout, true); ?>
-								</td>
+								<?php if ($defaultAssocLang) : ?>
+									<td>
+										<?php echo AssociationsHelper::getAssociationHtmlList($this->extensionName, $this->typeName, (int) $item->id, $item->language, !$isCheckout, true, $assocState); ?>
+									</td>
+								<?php else : ?>
+									<td>
+										<?php echo AssociationsHelper::getAssociationHtmlList($this->extensionName, $this->typeName, (int) $item->id, $item->language, !$isCheckout, false); ?>
+									</td>
+									<td>
+										<?php echo AssociationsHelper::getAssociationHtmlList($this->extensionName, $this->typeName, (int) $item->id, $item->language, !$isCheckout, true); ?>
+									</td>
+								<?php endif; ?>
 								<?php if (!empty($this->typeFields['menutype'])) : ?>
 									<td class="small">
 										<?php echo $this->escape($item->menutype_title); ?>
@@ -147,7 +160,7 @@
 						</tbody>
 					</table>
 
-					<?php // load the pagination. ?>
+					<?php // Load the pagination. ?>
 					<?php echo $this->pagination->getListFooter(); ?>
 
 				<?php endif; ?>
diff --git a/administrator/components/com_associations/tmpl/associations/modal.php b/administrator/components/com_associations/tmpl/associations/modal.php
index ed7c320393274..185949b729692 100644
--- a/administrator/components/com_associations/tmpl/associations/modal.php
+++ b/administrator/components/com_associations/tmpl/associations/modal.php
@@ -29,6 +29,7 @@
 $function         = $app->input->getCmd('function', 'jSelectAssociation');
 $listOrder        = $this->escape($this->state->get('list.ordering'));
 $listDirn         = $this->escape($this->state->get('list.direction'));
+$assocState       = $this->escape($this->state->get('assocstate'));
 $canManageCheckin = Factory::getUser()->authorise('core.manage', 'com_checkin');
 
 $iconStates = array(
@@ -131,7 +132,7 @@
 							</td>
 							<td>
 								<?php if (true || $item->association) : ?>
-									<?php echo AssociationsHelper::getAssociationHtmlList($this->extensionName, $this->typeName, (int) $item->id, $item->language, false, false); ?>
+									<?php echo AssociationsHelper::getAssociationHtmlList($this->extensionName, $this->typeName, (int) $item->id, $item->language, false, false, $assocState); ?>
 								<?php endif; ?>
 							</td>
 							<?php if (!empty($this->typeFields['menutype'])) : ?>
diff --git a/administrator/components/com_categories/Model/CategoryModel.php b/administrator/components/com_categories/Model/CategoryModel.php
index 8584d2abc2d2d..41c92ee075983 100644
--- a/administrator/components/com_categories/Model/CategoryModel.php
+++ b/administrator/components/com_categories/Model/CategoryModel.php
@@ -27,7 +27,9 @@
 use Joomla\CMS\MVC\Model\AdminModel;
 use Joomla\CMS\Plugin\PluginHelper;
 use Joomla\CMS\UCM\UCMType;
+use Joomla\Component\Associations\Administrator\Helper\DefaultAssocLangHelper;
 use Joomla\Component\Categories\Administrator\Helper\CategoriesHelper;
+use Joomla\Database\ParameterType;
 use Joomla\Registry\Registry;
 use Joomla\String\StringHelper;
 use Joomla\Utilities\ArrayHelper;
@@ -630,6 +632,9 @@ public function save($data)
 				Factory::getApplication()->enqueueMessage(Text::_('COM_CATEGORIES_ERROR_ALL_LANGUAGE_ASSOCIATED'), 'notice');
 			}
 
+			// Get association params before they get deleted
+			$assocParentDates = DefaultAssocLangHelper::getParentDates($associations, $this->associationsContext);
+
 			// Get associationskey for edited item
 			$db    = $this->getDbo();
 			$query = $db->getQuery(true)
@@ -677,27 +682,57 @@ public function save($data)
 
 			if (count($associations) > 1)
 			{
+				// If there is an association item with the default association language, then get its id
+				$defaultAssocLang = Associations::getDefaultAssocLang();
+				$parentId         = $associations[$defaultAssocLang] ?? '';
+
+				// Id of the saved item
+				$dataId = (int) $table->id;
+
+				// Get the latest modified date of parent
+				$parentModified = DefaultAssocLangHelper::getParentModifiedDate($parentId, $table->getTableName(), $table->extension . '.category');
+
 				// Adding new association for these items
 				$key = md5(json_encode($associations));
-				$query->clear()
-					->insert('#__associations');
 
 				foreach ($associations as $id)
 				{
-					$query->values(((int) $id) . ',' . $db->quote($this->associationsContext) . ',' . $db->quote($key));
-				}
+					$parentIdAndDateValues = DefaultAssocLangHelper::getParentValues(
+						$id, $dataId, $parentId, $parentModified, $assocParentDates, $oldKey
+					);
+					$parentIdValue         = $parentIdAndDateValues[0];
+					$parentDateValue       = $parentIdAndDateValues[1] === 'NULL' ? 'NULL' : Factory::getDate($parentIdAndDateValues[1])->toSql();
 
-				$db->setQuery($query);
+					$query->clear()
+						->insert($db->quoteName('#__associations'));
 
-				try
-				{
-					$db->execute();
-				}
-				catch (\RuntimeException $e)
-				{
-					$this->setError($e->getMessage());
+					if ($parentDateValue === 'NULL')
+					{
+						$query->values((' :id, :context, :key, :parentId, NULL'));
+					}
+					else
+					{
+						$query->values((' :id, :context, :key, :parentId, :parentDate'))
+							->bind(':parentDate', $parentDateValue);
+					}
 
-					return false;
+					$query->bind(':id', $id, ParameterType::INTEGER)
+						->bind(':context', $this->associationsContext)
+						->bind(':key', $key)
+						->bind(':parentId', $parentIdValue, ParameterType::INTEGER);
+
+					$db->setQuery($query);
+
+					try
+					{
+						$db->execute();
+					}
+					catch (\RuntimeException $e)
+					{
+						$this->setError($e->getMessage());
+
+						return false;
+					}
 				}
 			}
 		}
diff --git a/administrator/components/com_categories/Service/HTML/AdministratorService.php b/administrator/components/com_categories/Service/HTML/AdministratorService.php
index ee5932ffb26dd..c3a2a2e60142e 100644
--- a/administrator/components/com_categories/Service/HTML/AdministratorService.php
+++ b/administrator/components/com_categories/Service/HTML/AdministratorService.php
@@ -11,10 +11,14 @@
 
 defined('_JEXEC') or die;
 
+use Joomla\CMS\Component\ComponentHelper;
 use Joomla\CMS\Factory;
+use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Layout\LayoutHelper;
 use Joomla\CMS\Router\Route;
+use Joomla\Component\Associations\Administrator\Helper\DefaultAssocLangHelper;
 use Joomla\Component\Categories\Administrator\Helper\CategoriesHelper;
+use Joomla\Database\ParameterType;
 use Joomla\Utilities\ArrayHelper;
 
 /**
@@ -38,7 +42,11 @@ class AdministratorService
 	public function association($catid, $extension = 'com_content')
 	{
 		// Defaults
-		$html = '';
+		$html             = '';
+		$defaultAssocLang = Associations::getDefaultAssocLang();
+
+		// Check if versions are enabled.
+		$saveHistory      = ComponentHelper::getParams($extension)->get('save_history', 0);
 
 		// Get the associations
 		if ($associations = CategoriesHelper::getAssociations($catid, $extension))
@@ -48,15 +56,19 @@ public function association($catid, $extension = 'com_content')
 			// Get the associated categories
 			$db = Factory::getDbo();
 			$query = $db->getQuery(true)
-				->select('c.id, c.title')
-				->select('l.sef as lang_sef')
-				->select('l.lang_code')
-				->from('#__categories as c')
-				->where('c.id IN (' . implode(',', array_values($associations)) . ')')
-				->where('c.id != ' . $catid)
-				->join('LEFT', '#__languages as l ON c.language=l.lang_code')
-				->select('l.image')
-				->select('l.title as language_title');
+				->select($db->quoteName(['c.id', 'c.title', 'l.lang_code', 'l.image']))
+				->select($db->quoteName(['l.sef', 'l.title'], ['lang_sef', 'language_title']))
+				->from($db->quoteName('#__categories', 'c'))
+				->whereIN($db->quoteName('c.id'), array_values($associations));
+
+			// Don't get the id of the item itself when there is no default association language used.
+			if (!$defaultAssocLang)
+			{
+				$query->where($db->quoteName('c.id') . ' != :id')
+					->bind(':id', $catid, ParameterType::INTEGER);
+			}
+
+			$query->leftJoin($db->quoteName('#__languages', 'l'), $db->quoteName('c.language') . ' = ' . $db->quoteName('l.lang_code'));
 			$db->setQuery($query);
 
 			try
@@ -68,18 +80,76 @@ public function association($catid, $extension = 'com_content')
 				throw new \Exception($e->getMessage(), 500, $e);
 			}
 
+			if ($defaultAssocLang)
+			{
+				// Check if the current item is a parent.
+				$isParent = (array_key_exists($catid, $items) && ($items[$catid]->lang_code === $defaultAssocLang))
+					? true
+					: false;
+
+				// Check if there is a parent in the association and get its id if so.
+				$parentId = array_key_exists($defaultAssocLang, $associations)
+					? $associations[$defaultAssocLang]
+					: '';
+
+				// Get parent dates of each item of associations.
+				$assocParentDates = DefaultAssocLangHelper::getParentDates($associations, 'com_categories.item');
+			}
+
 			if ($items)
 			{
-				foreach ($items as &$item)
+				foreach ($items as $key => &$item)
 				{
-					$text     = $item->lang_sef ? strtoupper($item->lang_sef) : 'XX';
-					$url      = Route::_('index.php?option=com_categories&task=category.edit&id=' . (int) $item->id . '&extension=' . $extension);
-					$tooltip  = '<strong>' . htmlspecialchars($item->language_title, ENT_QUOTES, 'UTF-8') . '</strong><br>'
-						. htmlspecialchars($item->title, ENT_QUOTES, 'UTF-8');
-					$classes  = 'badge badge-secondary';
+					$labelClass      = 'badge-success';
+					$parentChildInfo = '';
+					$url             = Route::_('index.php?option=com_categories&task=category.edit&id=' . (int) $item->id . '&extension=' . $extension);
+
+					if ($defaultAssocLang)
+					{
+						// Don't continue for parent, because it has been set here before.
+						if ($key === 'parent')
+						{
+							continue;
+						}
+
+						$classParentInfoItems = DefaultAssocLangHelper::setParentAndChildInfos(
+							$catid, $items, $key, $item, $defaultAssocLang, $isParent, $parentId, $assocParentDates, $saveHistory
+						);
+						$labelClass      = $classParentInfoItems[0];
+						$parentChildInfo = $classParentInfoItems[1];
+						$items           = $classParentInfoItems[2];
+						$needsUpdate     = $classParentInfoItems[3];
+
+						$url = Route::_(
+							DefaultAssocLangHelper::getAssociationUrl(
+								$item->id, $defaultAssocLang, $extension . '.category', $item->lang_code, $key, $parentId, $needsUpdate
+							)
+						);
+					}
+
+					$text    = $item->lang_sef ? strtoupper($item->lang_sef) : 'XX';
+					$tooltip = '<strong>' . htmlspecialchars($item->language_title, ENT_QUOTES, 'UTF-8') . '</strong><br>'
+						. htmlspecialchars($item->title, ENT_QUOTES, 'UTF-8') . $parentChildInfo;
+					$classes = 'badge ' . $labelClass;
 
 					$item->link = '<a href="' . $url . '" title="' . $item->language_title . '" class="' . $classes . '">' . $text . '</a>'
 						. '<div role="tooltip" id="tip' . (int) $item->id . '">' . $tooltip . '</div>';
+
+					// Reorder the array, so the parent gets to the first place.
+					if ($item->lang_code === $defaultAssocLang)
+					{
+						$items = array('parent' => $items[$key]) + $items;
+						unset($items[$key]);
+					}
+				}
+
+				// If a parent doesn't exist, display that there is no association with the default association language.
+				if ($defaultAssocLang && !$parentId)
+				{
+					$link = DefaultAssocLangHelper::addNotAssociatedParentLink($defaultAssocLang, $catid, $extension . '.category');
+
+					// Add this on the top of the array.
+					$items = array('parent' => array('link' => $link)) + $items;
 				}
 			}
 
diff --git a/administrator/components/com_categories/tmpl/categories/default.php b/administrator/components/com_categories/tmpl/categories/default.php
index 4548e2b72ec93..a181efe8ca69f 100644
--- a/administrator/components/com_categories/tmpl/categories/default.php
+++ b/administrator/components/com_categories/tmpl/categories/default.php
@@ -11,6 +11,7 @@
 
 use Joomla\CMS\Factory;
 use Joomla\CMS\HTML\HTMLHelper;
+use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Language\Multilanguage;
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\Layout\LayoutHelper;
@@ -20,15 +21,16 @@
 
 HTMLHelper::_('behavior.multiselect');
 
-$user      = Factory::getUser();
-$userId    = $user->get('id');
-$extension = $this->escape($this->state->get('filter.extension'));
-$listOrder = $this->escape($this->state->get('list.ordering'));
-$listDirn  = $this->escape($this->state->get('list.direction'));
-$saveOrder = ($listOrder == 'a.lft' && strtolower($listDirn) == 'asc');
-$parts     = explode('.', $extension, 2);
-$component = $parts[0];
-$section   = null;
+$user        = Factory::getUser();
+$userId      = $user->get('id');
+$extension   = $this->escape($this->state->get('filter.extension'));
+$listOrder   = $this->escape($this->state->get('list.ordering'));
+$listDirn    = $this->escape($this->state->get('list.direction'));
+$saveOrder   = ($listOrder == 'a.lft' && strtolower($listDirn) == 'asc');
+$parts       = explode('.', $extension, 2);
+$component   = $parts[0];
+$section     = null;
+$assocAlign = Associations::getDefaultAssocLang() ? 'text-center ' : '';
 
 if (count($parts) > 1)
 {
@@ -108,7 +110,7 @@
 									<?php echo HTMLHelper::_('searchtools.sort', 'JGRID_HEADING_ACCESS', 'access_level', $listDirn, $listOrder); ?>
 								</th>
 								<?php if ($this->assoc) : ?>
-									<th scope="col" style="width:10%" class="d-none d-md-table-cell">
+									<th scope="col" style="width:10%" class="<?php echo $assocAlign ?>d-none d-md-table-cell">
 										<?php echo HTMLHelper::_('searchtools.sort', 'COM_CATEGORY_HEADING_ASSOCIATION', 'association', $listDirn, $listOrder); ?>
 									</th>
 								<?php endif; ?>
diff --git a/administrator/components/com_contact/Service/HTML/AdministratorService.php b/administrator/components/com_contact/Service/HTML/AdministratorService.php
index 114313efd618e..b8cb94107b5f0 100644
--- a/administrator/components/com_contact/Service/HTML/AdministratorService.php
+++ b/administrator/components/com_contact/Service/HTML/AdministratorService.php
@@ -11,11 +11,14 @@
 
 defined('_JEXEC') or die;
 
+use Joomla\CMS\Component\ComponentHelper;
 use Joomla\CMS\Factory;
 use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\Layout\LayoutHelper;
 use Joomla\CMS\Router\Route;
+use Joomla\Component\Associations\Administrator\Helper\DefaultAssocLangHelper;
+use Joomla\Database\ParameterType;
 use Joomla\Utilities\ArrayHelper;
 
 /**
@@ -37,7 +40,11 @@ class AdministratorService
 	public function association($contactid)
 	{
 		// Defaults
-		$html = '';
+		$html             = '';
+		$defaultAssocLang = Associations::getDefaultAssocLang();
+
+		// Check if versions are enabled
+		$saveHistory      = ComponentHelper::getParams('com_contact')->get('save_history', 0);
 
 		// Get the associations
 		if ($associations = Associations::getAssociations('com_contact', '#__contact_details', 'com_contact.item', $contactid))
@@ -50,16 +57,20 @@ public function association($contactid)
 			// Get the associated contact items
 			$db = Factory::getDbo();
 			$query = $db->getQuery(true)
-				->select('c.id, c.name as title')
-				->select('l.sef as lang_sef, lang_code')
-				->from('#__contact_details as c')
-				->select('cat.title as category_title')
-				->join('LEFT', '#__categories as cat ON cat.id=c.catid')
-				->where('c.id IN (' . implode(',', array_values($associations)) . ')')
-				->where('c.id != ' . $contactid)
-				->join('LEFT', '#__languages as l ON c.language=l.lang_code')
-				->select('l.image')
-				->select('l.title as language_title');
+				->select($db->quoteName(['c.id', 'lang_code', 'l.image']))
+				->select($db->quoteName(['c.name', 'l.sef', 'cat.title', 'l.title'], ['title', 'lang_sef', 'category_title', 'language_title']))
+				->from($db->quoteName('#__contact_details', 'c'))
+				->leftJoin($db->quoteName('#__categories', 'cat'), $db->quoteName('cat.id') . ' = ' . $db->quoteName('c.catid'))
+				->whereIN($db->quoteName('c.id'), array_values($associations));
+
+			// Don't get the id of the item itself when there is no default association language used.
+			if (!$defaultAssocLang)
+			{
+				$query->where($db->quoteName('c.id') . ' != :id')
+					->bind(':id', $contactid, ParameterType::INTEGER);
+			}
+
+			$query->leftJoin($db->quoteName('#__languages', 'l'), $db->quoteName('c.language') . ' = ' . $db->quoteName('l.lang_code'));
 			$db->setQuery($query);
 
 			try
@@ -71,18 +82,76 @@ public function association($contactid)
 				throw new \Exception($e->getMessage(), 500, $e);
 			}
 
+			if ($defaultAssocLang)
+			{
+				// Check if current item is the parent.
+				$isParent = (array_key_exists($contactid, $items) && ($items[$contactid]->lang_code === $defaultAssocLang))
+					? true
+					: false;
+
+				// Check if there is a parent in the association and get its id if so.
+				$parentId = array_key_exists($defaultAssocLang, $associations)
+					? $associations[$defaultAssocLang]
+					: '';
+
+				// Get parent dates of each item of associations.
+				$assocParentDates = DefaultAssocLangHelper::getParentDates($associations, 'com_contact.item');
+			}
+
 			if ($items)
 			{
-				foreach ($items as &$item)
+				foreach ($items as $key => &$item)
 				{
-					$text = strtoupper($item->lang_sef);
-					$url = Route::_('index.php?option=com_contact&task=contact.edit&id=' . (int) $item->id);
+					$parentChildInfo = '';
+					$labelClass      = 'badge-success';
+					$url             = Route::_('index.php?option=com_contact&task=contact.edit&id=' . (int) $item->id);
+
+					if ($defaultAssocLang)
+					{
+						// Don't continue for parent, because it has been set just before as new array item
+						if ($key === 'parent')
+						{
+							continue;
+						}
+
+						$classParentInfoItems = DefaultAssocLangHelper::setParentAndChildInfos(
+							$contactid, $items, $key, $item, $defaultAssocLang, $isParent, $parentId, $assocParentDates, $saveHistory
+						);
+						$labelClass       = $classParentInfoItems[0];
+						$parentChildInfo  = $classParentInfoItems[1];
+						$items            = $classParentInfoItems[2];
+						$needsUpdate      = $classParentInfoItems[3];
+
+						$url = Route::_(
+							DefaultAssocLangHelper::getAssociationUrl(
+								$item->id, $defaultAssocLang, 'com_contact.contact', $item->lang_code, $key, $parentId, $needsUpdate
+							)
+						);
+					}
+
+					$text    = strtoupper($item->lang_sef);
 					$tooltip = '<strong>' . htmlspecialchars($item->language_title, ENT_QUOTES, 'UTF-8') . '</strong><br>'
-						. htmlspecialchars($item->title, ENT_QUOTES, 'UTF-8') . '<br>' . Text::sprintf('JCATEGORY_SPRINTF', $item->category_title);
-					$classes = 'badge badge-secondary';
+						. htmlspecialchars($item->title, ENT_QUOTES, 'UTF-8') . '<br>' . Text::sprintf('JCATEGORY_SPRINTF', $item->category_title) . $parentChildInfo;
+					$classes = 'badge ' . $labelClass;
 
 					$item->link = '<a href="' . $url . '" title="' . $item->language_title . '" class="' . $classes . '">' . $text . '</a>'
 						. '<div role="tooltip" id="tip' . (int) $item->id . '">' . $tooltip . '</div>';
+
+					// Reorder the array, so the parent gets to the first place
+					if ($item->lang_code === $defaultAssocLang)
+					{
+						$items = array('parent' => $items[$key]) + $items;
+						unset($items[$key]);
+					}
+				}
+
+				// If a parent doesn't exist, display that there is no association with the default association language.
+				if ($defaultAssocLang && !$parentId)
+				{
+					$link = DefaultAssocLangHelper::addNotAssociatedParentLink($defaultAssocLang, $contactid, 'com_contact.contact');
+
+					// Add this on the top of the array
+					$items = array('parent' => array('link' => $link)) + $items;
 				}
 			}
 
diff --git a/administrator/components/com_content/Service/HTML/AdministratorService.php b/administrator/components/com_content/Service/HTML/AdministratorService.php
index 6b4ee27979972..b0ed7a8328236 100644
--- a/administrator/components/com_content/Service/HTML/AdministratorService.php
+++ b/administrator/components/com_content/Service/HTML/AdministratorService.php
@@ -11,11 +11,15 @@
 
 defined('_JEXEC') or die;
 
+use Joomla\CMS\Component\ComponentHelper;
 use Joomla\CMS\Factory;
 use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\Layout\LayoutHelper;
 use Joomla\CMS\Router\Route;
+use Joomla\Component\Associations\Administrator\Helper\DefaultAssocLangHelper;
+use Joomla\Database\ParameterType;
+use Joomla\Utilities\ArrayHelper;
 
 /**
  * Content HTML helper
@@ -37,7 +41,11 @@ class AdministratorService
 	public function association($articleid)
 	{
 		// Defaults
-		$html = '';
+		$html             = '';
+		$defaultAssocLang = Associations::getDefaultAssocLang();
+
+		// Check if versions are enabled
+		$saveHistory = ComponentHelper::getParams('com_content')->get('save_history', 0);
 
 		// Get the associations
 		if ($associations = Associations::getAssociations('com_content', '#__content', 'com_content.item', $articleid))
@@ -51,16 +59,20 @@ public function association($articleid)
 			$db = Factory::getDbo();
 			$query = $db->getQuery(true)
 				->select('c.*')
-				->select('l.sef as lang_sef')
-				->select('l.lang_code')
-				->from('#__content as c')
-				->select('cat.title as category_title')
-				->join('LEFT', '#__categories as cat ON cat.id=c.catid')
-				->where('c.id IN (' . implode(',', array_values($associations)) . ')')
-				->where('c.id != ' . $articleid)
-				->join('LEFT', '#__languages as l ON c.language=l.lang_code')
-				->select('l.image')
-				->select('l.title as language_title');
+				->select($db->quoteName(['l.lang_code', 'l.image']))
+				->select($db->quoteName(['l.sef', 'cat.title', 'l.title'], ['lang_sef', 'category_title', 'language_title']))
+				->from($db->quoteName('#__content', 'c'))
+				->leftJoin($db->quoteName('#__categories', 'cat'), $db->quoteName('cat.id') . ' = ' . $db->quoteName('c.catid'))
+				->whereIN($db->quoteName('c.id'), array_values($associations));
+
+			// Don't get the id of the item itself when there is no default association language used.
+			if (!$defaultAssocLang)
+			{
+				$query->where($db->quoteName('c.id') . ' != :id')
+					->bind(':id', $articleid, ParameterType::INTEGER);
+			}
+
+			$query->leftJoin($db->quoteName('#__languages', 'l'), $db->quoteName('c.language') . ' = ' . $db->quoteName('l.lang_code'));
 			$db->setQuery($query);
 
 			try
@@ -72,18 +84,76 @@ public function association($articleid)
 				throw new \Exception($e->getMessage(), 500, $e);
 			}
 
+			if ($defaultAssocLang)
+			{
+				// Check if the current item is a parent.
+				$isParent = (array_key_exists($articleid, $items) && ($items[$articleid]->lang_code === $defaultAssocLang))
+					? true
+					: false;
+
+				// Check if there is a parent in the association and get its id if so
+				$parentId = array_key_exists($defaultAssocLang, $associations)
+					? $associations[$defaultAssocLang]
+					: '';
+
+				// Get parent dates of each item of associations.
+				$assocParentDates = DefaultAssocLangHelper::getParentDates($associations, 'com_content.item');
+			}
+
 			if ($items)
 			{
-				foreach ($items as &$item)
+				foreach ($items as $key => &$item)
 				{
+					$parentChildInfo = '';
+					$labelClass      = 'badge-success';
+					$url             = Route::_('index.php?option=com_content&task=article.edit&id=' . (int) $item->id);
+
+					if ($defaultAssocLang)
+					{
+						// Don't continue for parent, because it has been set here before
+						if ($key === 'parent')
+						{
+							continue;
+						}
+
+						$classParentInfoItems = DefaultAssocLangHelper::setParentAndChildInfos(
+							$articleid, $items, $key, $item, $defaultAssocLang, $isParent, $parentId, $assocParentDates, $saveHistory
+						);
+						$labelClass      = $classParentInfoItems[0];
+						$parentChildInfo = $classParentInfoItems[1];
+						$items           = $classParentInfoItems[2];
+						$needsUpdate     = $classParentInfoItems[3];
+
+						$url = Route::_(
+							DefaultAssocLangHelper::getAssociationUrl(
+								$item->id, $defaultAssocLang, 'com_content.article', $item->lang_code, $key, $parentId, $needsUpdate
+							)
+						);
+					}
+
 					$text    = $item->lang_sef ? strtoupper($item->lang_sef) : 'XX';
-					$url     = Route::_('index.php?option=com_content&task=article.edit&id=' . (int) $item->id);
 					$tooltip = '<strong>' . htmlspecialchars($item->language_title, ENT_QUOTES, 'UTF-8') . '</strong><br>'
-						. htmlspecialchars($item->title, ENT_QUOTES, 'UTF-8') . '<br>' . Text::sprintf('JCATEGORY_SPRINTF', $item->category_title);
-					$classes = 'badge badge-secondary';
+						. htmlspecialchars($item->title, ENT_QUOTES, 'UTF-8') . '<br>' . Text::sprintf('JCATEGORY_SPRINTF', $item->category_title) . $parentChildInfo;
+					$classes = 'badge ' . $labelClass;
 
 					$item->link = '<a href="' . $url . '" title="' . $item->language_title . '" class="' . $classes . '">' . $text . '</a>'
 						. '<div role="tooltip" id="tip' . (int) $item->id . '">' . $tooltip . '</div>';
+
+					// Reorder the array, so the parent gets to the first place
+					if ($item->lang_code === $defaultAssocLang)
+					{
+						$items = array('parent' => $items[$key]) + $items;
+						unset($items[$key]);
+					}
+				}
+
+				// If a parent doesn't exist, display that there is no association with the default association language.
+				if ($defaultAssocLang && !$parentId)
+				{
+					$link = DefaultAssocLangHelper::addNotAssociatedParentLink($defaultAssocLang, $articleid, 'com_content.article');
+
+					// Add this on the top of the array
+					$items = array('parent' => array('link' => $link)) + $items;
 				}
 			}
 
diff --git a/administrator/components/com_contenthistory/tmpl/compare/compareassocparent.php b/administrator/components/com_contenthistory/tmpl/compare/compareassocparent.php
new file mode 100644
index 0000000000000..82317cf975fe9
--- /dev/null
+++ b/administrator/components/com_contenthistory/tmpl/compare/compareassocparent.php
@@ -0,0 +1,97 @@
+<?php
+/**
+ * @package     Joomla.Administrator
+ * @subpackage  com_contenthistory
+ *
+ * @copyright   Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+defined('_JEXEC') or die;
+
+use Joomla\CMS\HTML\HTMLHelper;
+use Joomla\CMS\Language\Text;
+use Joomla\CMS\Session\Session;
+
+Session::checkToken('get') or die(Text::_('JINVALID_TOKEN'));
+
+$version2 = $this->items[0];
+$version1 = $this->items[1];
+$object1  = $version1->data;
+$object2  = $version2->data;
+
+$objLabel = '';
+if (array_key_exists('title', $object2))
+{
+	$objLabel = $object2->title;
+}
+elseif (array_key_exists('name', $object2))
+{
+	$objLabel = $object2->name;
+}
+
+HTMLHelper::_('script', 'vendor/diff/diff.min.js', array('version' => 'auto', 'relative' => true));
+HTMLHelper::_('script', 'com_associations/admin-compare-assoc-parent.min.js', array('version' => 'auto', 'relative' => true));
+HTMLHelper::_('stylesheet', 'com_associations/sidebyside.css', ['version' => 'auto', 'relative' => true]);
+?>
+
+<div class="m-t-2 m-b-3">
+	<div class="control-group">
+		<div class="control-label">
+			<?php echo $objLabel->label ?>
+		</div>
+		<div class="controls">
+			<input type="text" value="<?php echo $objLabel->value ?>" class="form-control" disabled>
+		</div>
+	</div>
+	<div class="control-group">
+		<div class="control-label">
+			<?php echo $version2->data->alias->label ?>
+		</div>
+		<div class="controls">
+			<input type="text" value="<?php echo $version2->data->alias->value ?>" class="form-control" disabled>
+		</div>
+	</div>
+</div>
+<table id="diff" class="table table-sm">
+	<thead>
+	<tr>
+		<th style="width:25%"><?php echo Text::_('COM_CONTENTHISTORY_PREVIEW_FIELD'); ?></th>
+		<th><?php echo Text::_('COM_CONTENTHISTORY_COMPARE_DIFF'); ?></th>
+	</tr>
+	</thead>
+	<tbody>
+	<?php foreach ($object1 as $name => $value) : ?>
+		<?php if ($value->value != $object2->$name->value) : ?>
+			<tr>
+			<?php if (is_object($value->value)) : ?>
+				<td>
+					<strong><?php echo $value->label; ?></strong>
+				</td>
+				<?php foreach ($value->value as $subName => $subValue) : ?>
+					<?php $newSubValue = $object2->$name->value->$subName->value ?? ''; ?>
+					<?php if ($subValue->value || $newSubValue) : ?>
+						<?php if ($subValue->value != $newSubValue) : ?>
+							<tr>
+								<td><em><?php echo $subValue->label; ?></em></td>
+								<td class="original hidden"><?php echo htmlspecialchars($subValue->value, ENT_COMPAT, 'UTF-8'); ?></td>
+								<td class="changed hidden"><?php echo htmlspecialchars($newSubValue, ENT_COMPAT, 'UTF-8'); ?></td>
+								<td class="diff"></td>
+							</tr>
+						<?php endif; ?>
+					<?php endif; ?>
+				<?php endforeach; ?>
+			<?php else : ?>
+				<td>
+					<strong><?php echo $value->label; ?></strong>
+				</td>
+				<td class="original hidden"><?php echo htmlspecialchars($value->value); ?></td>
+				<?php $object2->$name->value = is_object($object2->$name->value) ? json_encode($object2->$name->value) : $object2->$name->value; ?>
+				<td class="changed hidden"><?php echo htmlspecialchars($object2->$name->value, ENT_COMPAT, 'UTF-8'); ?></td>
+				<td class="diff"></td>
+			<?php endif; ?>
+			</tr>
+		<?php endif; ?>
+	<?php endforeach; ?>
+	</tbody>
+</table>
diff --git a/administrator/components/com_menus/Model/ItemModel.php b/administrator/components/com_menus/Model/ItemModel.php
index 528e2be1f63df..a3f654a023b0b 100644
--- a/administrator/components/com_menus/Model/ItemModel.php
+++ b/administrator/components/com_menus/Model/ItemModel.php
@@ -23,6 +23,7 @@
 use Joomla\CMS\Plugin\PluginHelper;
 use Joomla\CMS\Uri\Uri;
 use Joomla\Component\Menus\Administrator\Helper\MenusHelper;
+use Joomla\Database\ParameterType;
 use Joomla\Registry\Registry;
 use Joomla\String\StringHelper;
 use Joomla\Utilities\ArrayHelper;
@@ -1580,27 +1581,38 @@ public function save($data)
 
 			if (count($associations) > 1)
 			{
+				// If there is an associated item with the default association language, get its id.
+				$defaultAssocLang = Associations::getDefaultAssocLang();
+				$parentId = $associations[$defaultAssocLang] ?? '';
+
 				// Adding new association for these items
 				$key = md5(json_encode($associations));
-				$query->clear()
-					->insert('#__associations');
 
 				foreach ($associations as $id)
 				{
-					$query->values(((int) $id) . ',' . $db->quote($this->associationsContext) . ',' . $db->quote($key));
-				}
-
-				$db->setQuery($query);
-
-				try
-				{
-					$db->execute();
-				}
-				catch (\RuntimeException $e)
-				{
-					$this->setError($e->getMessage());
+					// If there is no parent in this association, then reset the parent id.
+					// Otherwise, if the associated item is a parent, set its parent id to 0, otherwise to the parent Id.
+					$parentIdValue = $parentId ? ($parentId === $id ? 0 : $parentId) : -1;
+					$query->clear()
+						->insert($db->quoteName('#__associations'))
+						->values((' :id, :context, :key, :parentId, NULL'))
+						->bind(':id', $id, ParameterType::INTEGER)
+						->bind(':context', $this->associationsContext)
+						->bind(':key', $key)
+						->bind(':parentId', $parentIdValue, ParameterType::INTEGER);
+
+					$db->setQuery($query);
+
+					try
+					{
+						$db->execute();
+					}
+					catch (\RuntimeException $e)
+					{
+						$this->setError($e->getMessage());
 
-					return false;
+						return false;
+					}
 				}
 			}
 		}
diff --git a/administrator/components/com_menus/Service/HTML/Menus.php b/administrator/components/com_menus/Service/HTML/Menus.php
index 98581db575172..f119cffd3c11a 100644
--- a/administrator/components/com_menus/Service/HTML/Menus.php
+++ b/administrator/components/com_menus/Service/HTML/Menus.php
@@ -12,10 +12,13 @@
 defined('_JEXEC') or die;
 
 use Joomla\CMS\Factory;
+use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\Layout\LayoutHelper;
 use Joomla\CMS\Router\Route;
+use Joomla\Component\Associations\Administrator\Helper\DefaultAssocLangHelper;
 use Joomla\Component\Menus\Administrator\Helper\MenusHelper;
+use Joomla\Database\ParameterType;
 use Joomla\Registry\Registry;
 
 /**
@@ -42,6 +45,7 @@ public function association($itemid)
 	{
 		// Defaults
 		$html = '';
+		$defaultAssocLang = Associations::getDefaultAssocLang();
 
 		// Get the associations
 		if ($associations = MenusHelper::getAssociations($itemid))
@@ -49,16 +53,20 @@ public function association($itemid)
 			// Get the associated menu items
 			$db = Factory::getDbo();
 			$query = $db->getQuery(true)
-				->select('m.id, m.title')
-				->select('l.sef as lang_sef, l.lang_code')
-				->select('mt.title as menu_title')
-				->from('#__menu as m')
-				->join('LEFT', '#__menu_types as mt ON mt.menutype=m.menutype')
-				->where('m.id IN (' . implode(',', array_values($associations)) . ')')
-				->where('m.id != ' . $itemid)
-				->join('LEFT', '#__languages as l ON m.language=l.lang_code')
-				->select('l.image')
-				->select('l.title as language_title');
+				->select($db->quoteName(['m.id', 'm.title', 'l.lang_code', 'l.image']))
+				->select($db->quoteName(['l.sef', 'mt.title', 'l.title'], ['lang_sef', 'menu_title', 'language_title']))
+				->from($db->quoteName('#__menu', 'm'))
+				->leftJoin($db->quoteName('#__menu_types', 'mt'), $db->quoteName('mt.menutype') . ' = ' . $db->quoteName('m.menutype'))
+				->whereIN($db->quoteName('m.id'), array_values($associations));
+
+			// Don't get the id of the item itself when there is no default association language used
+			if (!$defaultAssocLang)
+			{
+				$query->where($db->quoteName('m.id') . ' != :id')
+					->bind(':id', $itemid, ParameterType::INTEGER);
+			}
+
+			$query->leftJoin($db->quoteName('#__languages', 'l'), $db->quoteName('m.language') . ' = ' . $db->quoteName('l.lang_code'));
 			$db->setQuery($query);
 
 			try
@@ -70,19 +78,74 @@ public function association($itemid)
 				throw new \Exception($e->getMessage(), 500);
 			}
 
+			if ($defaultAssocLang)
+			{
+				// Check if current item is the parent.
+				$isParent = (array_key_exists($itemid, $items) && ($items[$itemid]->lang_code === $defaultAssocLang))
+					? true
+					: false;
+
+				// Check if there is a parent in the association and get its id if so
+				$parentId = array_key_exists($defaultAssocLang, $associations)
+					? $associations[$defaultAssocLang]
+					: '';
+			}
+
 			// Construct html
 			if ($items)
 			{
-				foreach ($items as &$item)
+				foreach ($items as $key => &$item)
 				{
+					$parentChildInfo = '';
+					$classes    = 'badge badge-success';
+					$url        = Route::_('index.php?option=com_menus&task=item.edit&id=' . (int) $item->id);
+
+					if ($defaultAssocLang)
+					{
+						// Don't continue for parent, because it has been set here before
+						if ($key === 'parent')
+						{
+							continue;
+						}
+
+						// Don't display other children if the current item is a child.
+						if ($key !== $itemid && $defaultAssocLang !== $item->lang_code && !$isParent)
+						{
+							unset($items[$key]);
+						}
+
+						if ($key === $parentId)
+						{
+							$classes   .= ' parent-item';
+							$parentChildInfo = '<br><br>' . Text::_('JGLOBAL_ASSOCIATIONS_DEFAULT_ASSOC_LANG_ITEM');
+						}
+
+						$url = Route::_(DefaultAssocLangHelper::getAssociationUrl($item->id, $defaultAssocLang, 'com_menus.item', $item->lang_code, $key, $parentId));
+					}
+
 					$text    = strtoupper($item->lang_sef);
-					$url     = Route::_('index.php?option=com_menus&task=item.edit&id=' . (int) $item->id);
 					$tooltip = '<strong>' . htmlspecialchars($item->language_title, ENT_QUOTES, 'UTF-8') . '</strong><br>'
-						. htmlspecialchars($item->title, ENT_QUOTES, 'UTF-8') . '<br>' . Text::sprintf('COM_MENUS_MENU_SPRINTF', $item->menu_title);
-					$classes = 'badge badge-secondary';
+						. htmlspecialchars($item->title, ENT_QUOTES, 'UTF-8') . '<br>' . Text::sprintf('COM_MENUS_MENU_SPRINTF', $item->menu_title)
+						. $parentChildInfo;
 
 					$item->link = '<a href="' . $url . '" title="' . $item->language_title . '" class="' . $classes . '">' . $text . '</a>'
 						. '<div role="tooltip" id="tip' . (int) $item->id . '">' . $tooltip . '</div>';
+
+					// Reorder the array, so the parent gets to the first place
+					if ($item->lang_code === $defaultAssocLang)
+					{
+						$items = array('parent' => $items[$key]) + $items;
+						unset($items[$key]);
+					}
+				}
+
+				// If a parent doesn't exist, display that there is no association with the default association language.
+				if ($defaultAssocLang && !$parentId)
+				{
+					$link = DefaultAssocLangHelper::addNotAssociatedParentLink($defaultAssocLang, $itemid, 'com_menus.item');
+
+					// Add this on the top of the array
+					$items = array('parent' => array('link' => $link)) + $items;
 				}
 			}
 
diff --git a/administrator/components/com_newsfeeds/Service/HTML/AdministratorService.php b/administrator/components/com_newsfeeds/Service/HTML/AdministratorService.php
index ad9473e5f27b2..ab3dd0df6cfa7 100644
--- a/administrator/components/com_newsfeeds/Service/HTML/AdministratorService.php
+++ b/administrator/components/com_newsfeeds/Service/HTML/AdministratorService.php
@@ -11,11 +11,14 @@
 
 defined('_JEXEC') or die;
 
+use Joomla\CMS\Component\ComponentHelper;
 use Joomla\CMS\Factory;
 use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\Layout\LayoutHelper;
 use Joomla\CMS\Router\Route;
+use Joomla\Component\Associations\Administrator\Helper\DefaultAssocLangHelper;
+use Joomla\Database\ParameterType;
 
 /**
  * Utility class for creating HTML Grids.
@@ -36,7 +39,11 @@ class AdministratorService
 	public function association($newsfeedid)
 	{
 		// Defaults
-		$html = '';
+		$html             = '';
+		$defaultAssocLang = Associations::getDefaultAssocLang();
+
+		// Check if versions are enabled
+		$saveHistory = ComponentHelper::getParams('com_newsfeeds')->get('save_history', 0);
 
 		// Get the associations
 		if ($associations = Associations::getAssociations('com_newsfeeds', '#__newsfeeds', 'com_newsfeeds.item', $newsfeedid))
@@ -49,16 +56,20 @@ public function association($newsfeedid)
 			// Get the associated newsfeed items
 			$db = Factory::getDbo();
 			$query = $db->getQuery(true)
-				->select('c.id, c.name as title')
-				->select('l.sef as lang_sef, lang_code')
-				->from('#__newsfeeds as c')
-				->select('cat.title as category_title')
-				->join('LEFT', '#__categories as cat ON cat.id=c.catid')
-				->where('c.id IN (' . implode(',', array_values($associations)) . ')')
-				->where('c.id != ' . $newsfeedid)
-				->join('LEFT', '#__languages as l ON c.language=l.lang_code')
-				->select('l.image')
-				->select('l.title as language_title');
+				->select($db->quoteName(['c.id', 'lang_code', 'l.image']))
+				->select($db->quoteName(['c.name', 'l.sef', 'cat.title', 'l.title'], ['title', 'lang_sef', 'category_title', 'language_title']))
+				->from($db->quoteName('#__newsfeeds', 'c'))
+				->leftJoin($db->quoteName('#__categories', 'cat'), $db->quoteName('cat.id') . ' = ' . $db->quoteName('c.catid'))
+				->whereIN($db->quoteName('c.id'), array_values($associations));
+
+			// Don't get the id of the item itself when there is no default association language used
+			if (!$defaultAssocLang)
+			{
+				$query->where($db->quoteName('c.id') . ' != :id')
+					->bind(':id', $newsfeedid, ParameterType::INTEGER);
+			}
+
+			$query->leftJoin($db->quoteName('#__languages', 'l'), $db->quoteName('c.language') . ' = ' . $db->quoteName('l.lang_code'));
 			$db->setQuery($query);
 
 			try
@@ -70,18 +81,76 @@ public function association($newsfeedid)
 				throw new \Exception($e->getMessage(), 500);
 			}
 
+			if ($defaultAssocLang)
+			{
+				// Check if current item is a parent.
+				$isParent = (array_key_exists($newsfeedid, $items) && ($items[$newsfeedid]->lang_code === $defaultAssocLang))
+					? true
+					: false;
+
+				// Check if there is a parent in the association and get its id if so.
+				$parentId = array_key_exists($defaultAssocLang, $associations)
+					? $associations[$defaultAssocLang]
+					: '';
+
+				// Get parent dates of each item of associations.
+				$assocParentDates = DefaultAssocLangHelper::getParentDates($associations, 'com_newsfeeds.item');
+			}
+
 			if ($items)
 			{
-				foreach ($items as &$item)
+				foreach ($items as $key => &$item)
 				{
+					$parentChildInfo = '';
+					$labelClass = 'badge-success';
+					$url        = Route::_('index.php?option=com_newsfeeds&task=newsfeed.edit&id=' . (int) $item->id);
+
+					if ($defaultAssocLang)
+					{
+						// Don't continue for parent, because it has been set here before
+						if ($key === 'parent')
+						{
+							continue;
+						}
+
+						$classParentInfoItems = DefaultAssocLangHelper::setParentAndChildInfos(
+							$newsfeedid, $items, $key, $item, $defaultAssocLang, $isParent, $parentId, $assocParentDates, $saveHistory
+						);
+						$labelClass      = $classParentInfoItems[0];
+						$parentChildInfo = $classParentInfoItems[1];
+						$items           = $classParentInfoItems[2];
+						$needsUpdate     = $classParentInfoItems[3];
+
+						$url = Route::_(
+							DefaultAssocLangHelper::getAssociationUrl(
+								$item->id, $defaultAssocLang, 'com_newsfeeds.newsfeed', $item->lang_code, $key, $parentId, $needsUpdate
+							)
+						);
+					}
+
 					$text    = strtoupper($item->lang_sef);
-					$url     = Route::_('index.php?option=com_newsfeeds&task=newsfeed.edit&id=' . (int) $item->id);
 					$tooltip = '<strong>' . htmlspecialchars($item->language_title, ENT_QUOTES, 'UTF-8') . '</strong><br>'
-						. htmlspecialchars($item->title, ENT_QUOTES, 'UTF-8') . '<br>' . Text::sprintf('JCATEGORY_SPRINTF', $item->category_title);
-					$classes = 'badge badge-secondary';
+						. htmlspecialchars($item->title, ENT_QUOTES, 'UTF-8') . '<br>' . Text::sprintf('JCATEGORY_SPRINTF', $item->category_title) . $parentChildInfo;
+					$classes = 'badge ' . $labelClass;
 
 					$item->link = '<a href="' . $url . '" title="' . $item->language_title . '" class="' . $classes . '">' . $text . '</a>'
 						. '<div role="tooltip" id="tip' . (int) $item->id . '">' . $tooltip . '</div>';
+
+					// Reorder the array, so the parent gets to the first place
+					if ($item->lang_code === $defaultAssocLang)
+					{
+						$items = array('parent' => $items[$key]) + $items;
+						unset($items[$key]);
+					}
+				}
+
+				// If a parent doesn't exist, display that there is no association with the default association language.
+				if ($defaultAssocLang && !$parentId)
+				{
+					$link = DefaultAssocLangHelper::addNotAssociatedParentLink($defaultAssocLang, $newsfeedid, 'com_newsfeeds.newsfeed');
+
+					// Add this on the top of the array
+					$items = array('parent' => array('link' => $link)) + $items;
 				}
 			}
 
diff --git a/administrator/language/en-GB/en-GB.com_associations.ini b/administrator/language/en-GB/en-GB.com_associations.ini
index e7e2a25b6eb68..42746f785484e 100644
--- a/administrator/language/en-GB/en-GB.com_associations.ini
+++ b/administrator/language/en-GB/en-GB.com_associations.ini
@@ -19,8 +19,10 @@ COM_ASSOCIATIONS_EDIT_HIDE_REFERENCE="Hide Reference"
 COM_ASSOCIATIONS_EDIT_SHOW_REFERENCE="Show Reference"
 COM_ASSOCIATIONS_ERROR_NO_ASSOC="The Multilingual Associations component can't be used if the site is not set as multilingual and/or Associations is not enabled in the <a href=\"%s\">Language Filter plugin</a>."
 COM_ASSOCIATIONS_ERROR_NO_TYPE="The item type selected does not exist for this component."
+COM_ASSOCIATIONS_FILTER_ASSOCIATION_STATE="All Association States"
 COM_ASSOCIATIONS_FILTER_SEARCH_DESC="Search an item by its title"
 COM_ASSOCIATIONS_FILTER_SEARCH_LABEL="Search item"
+COM_ASSOCIATIONS_FILTER_SELECT_ASSOCIATION_STATE="- Select Association State -"
 COM_ASSOCIATIONS_FILTER_SELECT_ITEM="Select Item Type"
 COM_ASSOCIATIONS_FILTER_SELECT_ITEM_TYPE="- Select Item Type -"
 COM_ASSOCIATIONS_FILTER_SELECT_LANGUAGE="Select Language"
@@ -33,20 +35,26 @@ COM_ASSOCIATIONS_ITEMS="Items"
 COM_ASSOCIATIONS_NO_ASSOCIATION="There is no association for this language"
 COM_ASSOCIATIONS_NOTICE_NO_SELECTORS="Please select an Item Type and a reference language to view the associations."
 COM_ASSOCIATIONS_PURGE="Delete All Associations"
-COM_ASSOCIATIONS_PURGE_CONFIRM_PROMPT="Are you sure you want to delete all associations? Confirming will permanently delete them!"
+COM_ASSOCIATIONS_PURGE_CONFIRM_PROMPT="Are you sure you want to delete all associations concerning %s? Confirming will permanently delete them!"
 COM_ASSOCIATIONS_PURGE_FAILED="Failed to delete all associations."
 COM_ASSOCIATIONS_PURGE_NONE="There were no associations to delete."
 COM_ASSOCIATIONS_PURGE_SUCCESS="All associations have been deleted."
 COM_ASSOCIATIONS_REFERENCE_ITEM="Reference"
+COM_ASSOCIATIONS_REFERENCE_ITEM_COMPARE_VIEW="Reference - Compare View"
 COM_ASSOCIATIONS_SAVE_REFERENCE="Save Reference"
 COM_ASSOCIATIONS_SAVE_TARGET="Save Target"
+COM_ASSOCIATIONS_SAVE_AND_UPDATE_TARGET="Update Target and Close"
 COM_ASSOCIATIONS_SELECT_MENU="- Select Menu -"
 COM_ASSOCIATIONS_SELECT_TARGET="Select Target"
 COM_ASSOCIATIONS_SELECT_TARGET_LANGUAGE="- Select Target Language -"
+COM_ASSOCIATIONS_STATE_NOT_ASSOCIATED="Not Associated"
+COM_ASSOCIATIONS_STATE_OUT_OF_DATE="Out-of-date"
+COM_ASSOCIATIONS_STATE_UP_TO_DATE="Up-to-date"
 COM_ASSOCIATIONS_TABLE_CAPTION="Table of Associations"
 COM_ASSOCIATIONS_TITLE="Associations"
 COM_ASSOCIATIONS_TITLE_EDIT="Multilingual Associations: Edit Associations (%1s &gt; %2s)"
 COM_ASSOCIATIONS_TITLE_LIST="Multilingual Associations (%1s &gt; %2s)"
 COM_ASSOCIATIONS_TITLE_LIST_SELECT="Multilingual Associations: Select Item Type and Language"
+COM_ASSOCIATIONS_UPDATE_ASSOCIATION="Update Association"
 COM_ASSOCIATIONS_XML_DESCRIPTION="Improved multilingual content management component"
 COM_ASSOCIATIONS_YOU_ARE_NOT_ALLOWED_TO_CHECKIN_THIS_ITEM="You can't check in this item"
diff --git a/administrator/language/en-GB/en-GB.ini b/administrator/language/en-GB/en-GB.ini
index a97bba951cf6d..1314c08b7e4e6 100644
--- a/administrator/language/en-GB/en-GB.ini
+++ b/administrator/language/en-GB/en-GB.ini
@@ -281,6 +281,8 @@ JGLOBAL_ARTICLE_ORDER_DESC="The order that articles will show in."
 JGLOBAL_ARTICLE_ORDER_LABEL="Article Order"
 JGLOBAL_ARTICLES="Articles"
 JGLOBAL_ASSOC_NOT_POSSIBLE="To define associations, please make sure the item language is not set to 'All'."
+JGLOBAL_ASSOCIATIONS_DEFAULT_ASSOC_LANG="Default Association Language"
+JGLOBAL_ASSOCIATIONS_DEFAULT_ASSOC_LANG_ITEM="The Default Association Language"
 JGLOBAL_ASSOCIATIONS_NEW_ITEM_WARNING="To create associations, first save the item."
 JGLOBAL_ASSOCIATIONS_PROPAGATE_BUTTON="Propagate"
 JGLOBAL_ASSOCIATIONS_PROPAGATE_FAILED="Failed propagating associations. You may have to select or create them manually."
@@ -289,6 +291,10 @@ JGLOBAL_ASSOCIATIONS_PROPAGATE_MESSAGE_NONE="No associations exist to propagate.
 JGLOBAL_ASSOCIATIONS_PROPAGATE_MESSAGE_SOME="Associations have been set for: %s"
 JGLOBAL_ASSOCIATIONS_PROPAGATE_TIP="Propagates this item's existing associations."
 JGLOBAL_ASSOCIATIONS_RESET_WARNING="The language has been changed. If you save this item again it will reset the available associations. If this was not intended, close the item."
+JGLOBAL_ASSOCIATIONS_STATE_MIGHT_BE_OUT_OF_DATE_DESC="This item might be out-of-date with the item in the default association language."
+JGLOBAL_ASSOCIATIONS_STATE_NOT_ASSOCIATED_DESC="There is no association for the default association language."
+JGLOBAL_ASSOCIATIONS_STATE_OUT_OF_DATE_DESC="This item is out-of-date with the item in the default association language."
+JGLOBAL_ASSOCIATIONS_STATE_UP_TO_DATE_DESC="This item is up-to-date with the item in the default association language."
 JGLOBAL_AUTH_ACCESS_DENIED="Access Denied"
 JGLOBAL_AUTH_ACCESS_GRANTED="Access Granted"
 JGLOBAL_AUTH_BIND_FAILED="Failed binding to LDAP server"
diff --git a/administrator/language/en-GB/en-GB.plg_system_languagefilter.ini b/administrator/language/en-GB/en-GB.plg_system_languagefilter.ini
index 5b577e3384b53..358963750ab50 100644
--- a/administrator/language/en-GB/en-GB.plg_system_languagefilter.ini
+++ b/administrator/language/en-GB/en-GB.plg_system_languagefilter.ini
@@ -9,7 +9,11 @@ PLG_SYSTEM_LANGUAGEFILTER_FIELD_ALTERNATE_META_LABEL="Add Alternate Meta Tags"
 PLG_SYSTEM_LANGUAGEFILTER_FIELD_AUTOMATIC_CHANGE_LABEL="Automatic Language Change"
 PLG_SYSTEM_LANGUAGEFILTER_FIELD_COOKIE_LABEL="Cookie Lifetime"
 PLG_SYSTEM_LANGUAGEFILTER_FIELD_DETECT_BROWSER_LABEL="Language Selection for new Visitors"
+PLG_SYSTEM_LANGUAGEFILTER_FIELD_DEFAULT_ASSOC_LANG_LABEL="Default Association Language"
+PLG_SYSTEM_LANGUAGEFILTER_FIELD_DEFAULT_ASSOC_LANG_DESC="Note that changing this value will overwrite all existing parent-child relationships with their association states."
 PLG_SYSTEM_LANGUAGEFILTER_FIELD_ITEM_ASSOCIATIONS_LABEL="Item Associations"
+PLG_SYSTEM_LANGUAGEFILTER_FIELD_USE_DEFAULT_ASSOC_LANG_LABEL="Set a Default Association Language?"
+PLG_SYSTEM_LANGUAGEFILTER_FIELD_USE_DEFAULT_ASSOC_LANG_DESC="When enabled, a parent-child relationship is added between the languages. This adds additional 'out-of-date' and 'up-to-date' association state to a child depending on its parent. Enable versions to get a comparison view for out-of-date items. If this field is disabled, functions dependent on this data are not available."
 PLG_SYSTEM_LANGUAGEFILTER_FIELD_XDEFAULT_LABEL="Add x-default Meta Tag"
 PLG_SYSTEM_LANGUAGEFILTER_FIELD_XDEFAULT_LANGUAGE_LABEL="x-default Language"
 PLG_SYSTEM_LANGUAGEFILTER_OPTION_DEFAULT_LANGUAGE="Default frontend language"
diff --git a/administrator/templates/atum/scss/blocks/_global.scss b/administrator/templates/atum/scss/blocks/_global.scss
index 0ffefe53ba109..f8677f0dfb44a 100644
--- a/administrator/templates/atum/scss/blocks/_global.scss
+++ b/administrator/templates/atum/scss/blocks/_global.scss
@@ -132,11 +132,34 @@ body .container-main {
 // Multilingual associations specific
 .item-associations {
   padding: 0;
-}
+  margin-bottom: 0;
+
+  li, ul {
+    display: inline-block;
+    list-style: none;
+    padding: 0;
+  }
+
+  &.parent {
+    text-align: center;
+
+    div[role="tooltip"] {
+      text-align: left;
+    }
+  }
+
+  hr {
+    margin-top: 0.2rem;
+    margin-bottom: 0.2rem;
+  }
 
-.item-associations li {
-  display: inline-block;
-  list-style: none;
+  .parent-language {
+
+    & > a {
+      border-radius: 0;
+      padding-top: 0.2rem;
+    }
+  }
 }
 
 // Quickicon specific
diff --git a/administrator/templates/atum/scss/blocks/_searchtools.scss b/administrator/templates/atum/scss/blocks/_searchtools.scss
index 9da8a3644f2fc..373b63591c63b 100644
--- a/administrator/templates/atum/scss/blocks/_searchtools.scss
+++ b/administrator/templates/atum/scss/blocks/_searchtools.scss
@@ -82,6 +82,14 @@
     }
   }
 
+  .js-stools-container-selector-second {
+    margin-right: 8px;
+
+    html[dir=rtl] & {
+      margin-left: 8px;
+    }
+  }
+
   .js-stools-container-bar {
 
     .btn-toolbar {
diff --git a/build/media_source/com_associations/css/sidebyside.css b/build/media_source/com_associations/css/sidebyside.css
index c2ddde2af6da2..27df7eb024842 100644
--- a/build/media_source/com_associations/css/sidebyside.css
+++ b/build/media_source/com_associations/css/sidebyside.css
@@ -58,6 +58,21 @@ html[dir=rtl] .target-text {
 	float: right;
 }
 
+.diff .added {
+	background-color: #a6f3a6;
+	border-radius: .2rem;
+}
+
+.diff .removed {
+	background-color: #f8cbcb;
+	border-radius: .2rem;
+}
+
+.diff .same {
+	background-color: unset;
+	border-radius: 0;
+}
+
 /* Responsive layout */
 @media (max-width: 767px) {
 	.sidebyside .outer-panel {
diff --git a/build/media_source/com_associations/js/admin-associations-default.es6.js b/build/media_source/com_associations/js/admin-associations-default.es6.js
deleted file mode 100644
index cf078ebdd53f1..0000000000000
--- a/build/media_source/com_associations/js/admin-associations-default.es6.js
+++ /dev/null
@@ -1,18 +0,0 @@
-/**
- * @copyright   Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
- * @license     GNU General Public License version 2 or later; see LICENSE.txt
- */
-Joomla.submitbutton = (pressbutton) => {
-  if (pressbutton === 'associations.purge') {
-    // eslint-disable-next-line no-restricted-globals
-    if (confirm(Joomla.JText._('COM_ASSOCIATIONS_PURGE_CONFIRM_PROMPT'))) {
-      Joomla.submitform(pressbutton);
-    } else {
-      return false;
-    }
-  } else {
-    Joomla.submitform(pressbutton);
-  }
-
-  return true;
-};
diff --git a/build/media_source/com_associations/js/admin-compare-assoc-parent.es6.js b/build/media_source/com_associations/js/admin-compare-assoc-parent.es6.js
new file mode 100644
index 0000000000000..0a9fcc98fc6b9
--- /dev/null
+++ b/build/media_source/com_associations/js/admin-compare-assoc-parent.es6.js
@@ -0,0 +1,46 @@
+/**
+ * @copyright  Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
+ * @license    GNU General Public License version 2 or later; see LICENSE.txt
+ */
+(() => {
+  'use strict';
+
+  const compare = (original, changed) => {
+    const display = changed.nextElementSibling;
+    const tagName = 'mark';
+    let className = 'same';
+    let tagElement = null;
+
+    const diff = window.JsDiff.diffWords(original.textContent, changed.textContent);
+    const fragment = document.createDocumentFragment();
+
+    diff.forEach((part) => {
+      if (part.added) {
+        className = 'added';
+      }
+
+      if (part.removed) {
+        className = 'removed';
+      }
+
+      tagElement = document.createElement(tagName);
+      tagElement.setAttribute('class', className);
+      tagElement.appendChild(document.createTextNode(part.value));
+      fragment.appendChild(tagElement);
+    });
+
+    display.appendChild(fragment);
+  };
+
+  const onBoot = () => {
+    const diffs = [].slice.call(document.querySelectorAll('.original'));
+    diffs.forEach((fragment) => {
+      compare(fragment, fragment.nextElementSibling);
+    });
+
+    // Cleanup
+    document.removeEventListener('DOMContentLoaded', onBoot);
+  };
+
+  document.addEventListener('DOMContentLoaded', onBoot);
+})();
diff --git a/build/media_source/com_associations/js/sidebysideupdate.es6.js b/build/media_source/com_associations/js/sidebysideupdate.es6.js
new file mode 100644
index 0000000000000..65834eeaf8404
--- /dev/null
+++ b/build/media_source/com_associations/js/sidebysideupdate.es6.js
@@ -0,0 +1,60 @@
+/**
+ * @copyright   Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+Joomla = window.Joomla || {};
+
+((Joomla, document) => {
+  'use strict';
+
+  document.addEventListener('DOMContentLoaded', () => {
+    const referenceIframe = document.getElementById('reference-association');
+    const targetIframe = document.getElementById('target-association');
+
+    // Saving target, send the save action to the target iframe.
+    Joomla.submitbutton = (task) => {
+      // Using close button, normal joomla submit.
+      if (task === 'association.cancel') {
+        Joomla.submitform(task);
+      } else if (task === 'defaultAssocLang.update') {
+        Joomla.submitform(task);
+      } else {
+        window.frames['target-association'].Joomla.submitbutton(`${document.getElementById('adminForm').getAttribute('data-associatedview')}, .apply`);
+        document.getElementById('updateChild').click();
+      }
+    };
+
+    // Attach behaviour to reference frame load event.
+    referenceIframe.addEventListener('load', () => {
+      const reference = referenceIframe.contentDocument;
+      const referenceDiff = reference.querySelector('#diff');
+      // Waiting until the reference has loaded before loading the target to avoid race conditions
+
+      if (!referenceDiff) {
+        // Disable language field.
+        reference.querySelector('#jform_language').setAttribute('disabled', '');
+
+        // Remove modal buttons on the reference
+        reference.querySelector('#associations').querySelectorAll('.btn').forEach(e => e.parentNode.removeChild(e));
+      }
+
+      // Iframe load finished, hide Joomla loading layer.
+      Joomla.loadingLayer('hide');
+    });
+
+    targetIframe.addEventListener('load', () => {
+      if (targetIframe.getAttribute('src') !== '') {
+        const target = targetIframe.contentDocument;
+
+        // Update language field with the selected language and then disable it.
+        target.querySelector('#jform_language').setAttribute('disabled', '');
+
+        // Remove modal buttons on the reference
+        target.querySelector('#associations').querySelectorAll('.btn').forEach(e => e.parentNode.removeChild(e));
+
+        // Iframe load finished, hide Joomla loading layer.
+        Joomla.loadingLayer('hide');
+      }
+    });
+  });
+})(Joomla, document);
diff --git a/installation/sql/mysql/joomla.sql b/installation/sql/mysql/joomla.sql
index 56f5b81922026..bd958e68441e2 100644
--- a/installation/sql/mysql/joomla.sql
+++ b/installation/sql/mysql/joomla.sql
@@ -120,6 +120,8 @@ CREATE TABLE IF NOT EXISTS `#__associations` (
   `id` int(11) NOT NULL COMMENT 'A reference to the associated item.',
   `context` varchar(50) NOT NULL COMMENT 'The context of the associated item.',
   `key` char(32) NOT NULL COMMENT 'The key for the association computed from an md5 on associated ids.',
+  `parent_id` int(11) NOT NULL DEFAULT -1 COMMENT 'The parent of an association.',
+  `parent_date` datetime COMMENT 'The save or modified date of the parent.',
   PRIMARY KEY (`context`,`id`),
   KEY `idx_key` (`key`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 DEFAULT COLLATE=utf8mb4_unicode_ci;
diff --git a/installation/sql/postgresql/joomla.sql b/installation/sql/postgresql/joomla.sql
index b35c6cbb5cea4..0cea9919a2899 100644
--- a/installation/sql/postgresql/joomla.sql
+++ b/installation/sql/postgresql/joomla.sql
@@ -124,6 +124,8 @@ CREATE TABLE IF NOT EXISTS "#__associations" (
   "id" int NOT NULL,
   "context" varchar(50) NOT NULL,
   "key" char(32) NOT NULL,
+  "parent_id" integer DEFAULT -1 NOT NULL,
+  "parent_date" timestamp without time zone,
   CONSTRAINT "#__associations_idx_context_id" PRIMARY KEY ("context", "id")
 );
 CREATE INDEX "#__associations_idx_key" ON "#__associations" ("key");
@@ -131,6 +133,8 @@ CREATE INDEX "#__associations_idx_key" ON "#__associations" ("key");
 COMMENT ON COLUMN "#__associations"."id" IS 'A reference to the associated item.';
 COMMENT ON COLUMN "#__associations"."context" IS 'The context of the associated item.';
 COMMENT ON COLUMN "#__associations"."key" IS 'The key for the association computed from an md5 on associated ids.';
+COMMENT ON COLUMN "#__associations"."parent_id" IS 'The parent of an association.';
+COMMENT ON COLUMN "#__associations"."parent_date" IS 'The save or modified date of the parent.';
 
 --
 -- Table structure for table `#__banners`
diff --git a/installation/src/Model/LanguagesModel.php b/installation/src/Model/LanguagesModel.php
index 4726583540d4b..01572f5cfe383 100644
--- a/installation/src/Model/LanguagesModel.php
+++ b/installation/src/Model/LanguagesModel.php
@@ -17,6 +17,7 @@
 use Joomla\CMS\Form\Form;
 use Joomla\CMS\Installer\Installer;
 use Joomla\CMS\Installer\InstallerHelper;
+use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Language\Language;
 use Joomla\CMS\Language\LanguageHelper;
 use Joomla\CMS\Language\Text;
@@ -24,6 +25,7 @@
 use Joomla\CMS\Updater\Update;
 use Joomla\CMS\Updater\Updater;
 use Joomla\Database\Exception\ExecutionFailureException;
+use Joomla\Database\ParameterType;
 
 /**
  * Language Installer model for the Joomla Core Installer.
@@ -1405,27 +1407,38 @@ public function addBlogMenuItem($itemLanguage, $categoryId)
 	public function addAssociations($groupedAssociations)
 	{
 		$db = Factory::getDbo();
+		$defaultAssocLang = Associations::getDefaultAssocLang();
 
 		foreach ($groupedAssociations as $context => $associations)
 		{
-			$key   = md5(json_encode($associations));
-			$query = $db->getQuery(true)
-				->insert('#__associations');
+			// If there is an association item with the default association language, get its id.
+			$parentId = $associations[$defaultAssocLang] ?? '';
+			$key      = md5(json_encode($associations));
 
 			foreach ($associations as $language => $id)
 			{
-				$query->values(((int) $id) . ',' . $db->quote($context) . ',' . $db->quote($key));
-			}
-
-			$db->setQuery($query);
-
-			try
-			{
-				$db->execute();
-			}
-			catch (\RuntimeException $e)
-			{
-				return false;
+				// If there is no parent within this association, then reset the parent_id to -1
+				// Otherwise, if the associated item is a parent set the parent_id to 0, otherwise to the parentId.
+				$parentIdValue = $parentId ? ($parentId === $id ? 0 : $parentId) : -1;
+
+				$query = $db->getQuery(true)
+					->insert($db->quoteName('#__associations'))
+					->values((' :id, :context, :key, :parentId, NULL'))
+					->bind(':id', $id, ParameterType::INTEGER)
+					->bind(':context', $context)
+					->bind(':key', $key)
+					->bind(':parentId', $parentIdValue, ParameterType::INTEGER);
+
+				$db->setQuery($query);
+
+				try
+				{
+					$db->execute();
+				}
+				catch (\RuntimeException $e)
+				{
+					return false;
+				}
 			}
 		}
 
diff --git a/layouts/joomla/content/associations.php b/layouts/joomla/content/associations.php
index 9bd8cd3fa1138..f61a0ce4653f6 100644
--- a/layouts/joomla/content/associations.php
+++ b/layouts/joomla/content/associations.php
@@ -12,11 +12,28 @@
 $items = $displayData;
 
 if (!empty($items)) : ?>
-	<ul class="item-associations">
-		<?php foreach ($items as $id => $item) : ?>
-			<li>
-				<?php echo is_array($item) ? $item['link'] : $item->link; ?>
-			</li>
-		<?php endforeach; ?>
+		<?php if (array_key_first($items) === 'parent') : ?>
+			<ul class="item-associations parent">
+				<li class="parent-language">
+					<?php echo is_array(array_values($items)[0]) ? array_values($items)[0]['link'] : array_values($items)[0]->link; ?>
+					<hr>
+					<ul class="target-languages">
+						<?php foreach ($items as $id => $item) : ?>
+							<?php if ($id !== 'parent') : ?>
+								<li>
+									<?php echo is_array($item) ? $item['link'] : $item->link; ?>
+								</li>
+							<?php endif; ?>
+						<?php endforeach; ?>
+					</ul>
+				</li>
+		<?php else : ?>
+			<ul class="item-associations">
+				<?php foreach ($items as $id => $item) : ?>
+					<li>
+						<?php echo is_array($item) ? $item['link'] : $item->link; ?>
+					</li>
+				<?php endforeach; ?>
+		<?php endif; ?>
 	</ul>
 <?php endif; ?>
diff --git a/libraries/src/Language/Associations.php b/libraries/src/Language/Associations.php
index fe753a8a700bc..3a57e2aba19b4 100644
--- a/libraries/src/Language/Associations.php
+++ b/libraries/src/Language/Associations.php
@@ -43,6 +43,8 @@ public static function getAssociations($extension, $tablename, $context, $id, $p
 		$advClause = array()
 	)
 	{
+		$defaultAssocLang = self::getDefaultAssocLang();
+
 		// To avoid doing duplicate database queries.
 		static $multilanguageAssociations = array();
 
@@ -126,11 +128,19 @@ public static function getAssociations($extension, $tablename, $context, $id, $p
 			{
 				foreach ($items as $tag => $item)
 				{
-					// Do not return itself as result
-					if ((int) $item->{$pk} !== $id)
+					if ($defaultAssocLang)
 					{
+						// If a default association language is set, we need all items of an associations
 						$multilanguageAssociations[$queryKey][$tag] = $item;
 					}
+					else
+					{
+						// Do not return itself as result
+						if ((int) $item->{$pk} !== $id)
+						{
+							$multilanguageAssociations[$queryKey][$tag] = $item;
+						}
+					}
 				}
 			}
 		}
@@ -173,4 +183,39 @@ public static function isEnabled()
 
 		return $enabled;
 	}
+
+	/**
+	 * Method to get the default association language parameter for associations.
+	 *
+	 * @return  string  empty if not set, lang_code otherwise.
+	 *
+	 * @since   4.0
+	 */
+	public static function getDefaultAssocLang()
+	{
+		// Flag to avoid doing multiple database queries.
+		static $tested = false;
+
+		// Status of default association language parameter.
+		static $defaultAssocLang = '';
+
+		if (self::isEnabled())
+		{
+			// If already tested, don't test again.
+			if (!$tested)
+			{
+				$plugin = PluginHelper::getPlugin('system', 'languagefilter');
+
+				if (!empty($plugin))
+				{
+					$params = new Registry($plugin->params);
+					$defaultAssocLang  = $params->get('default_assoc_lang');
+				}
+
+				$tested = true;
+			}
+		}
+
+		return $defaultAssocLang ?? '';
+	}
 }
diff --git a/libraries/src/MVC/Model/AdminModel.php b/libraries/src/MVC/Model/AdminModel.php
index 0cd2934107de2..c33bc1d362c85 100644
--- a/libraries/src/MVC/Model/AdminModel.php
+++ b/libraries/src/MVC/Model/AdminModel.php
@@ -23,6 +23,8 @@
 use Joomla\CMS\Router\Route;
 use Joomla\CMS\Table\Table;
 use Joomla\CMS\UCM\UCMType;
+use Joomla\Component\Associations\Administrator\Helper\DefaultAssocLangHelper;
+use Joomla\Database\ParameterType;
 use Joomla\Registry\Registry;
 use Joomla\String\StringHelper;
 use Joomla\Utilities\ArrayHelper;
@@ -1319,6 +1321,12 @@ public function save($data)
 				);
 			}
 
+			// Get association params before they get deleted
+			if ($associations)
+			{
+				$assocParentDates = DefaultAssocLangHelper::getParentDates($associations, $this->associationsContext);
+			}
+
 			// Get associationskey for edited item
 			$db    = $this->getDbo();
 			$query = $db->getQuery(true)
@@ -1356,18 +1364,49 @@ public function save($data)
 
 			if (count($associations) > 1)
 			{
+				// If there is an associated item with the default association language, then get its id
+				$defaultAssocLang = Associations::getDefaultAssocLang();
+				$parentId         = $associations[$defaultAssocLang] ?? '';
+
+				// Get id of the item that get saved
+				$dataId           = (int) $table->id;
+
+				// Get the latest modified date of the parent
+				$parentModified   = DefaultAssocLangHelper::getParentModifiedDate($parentId, $table->getTableName(), $table->typeAlias);
+
 				// Adding new association for these items
-				$key   = md5(json_encode($associations));
-				$query = $db->getQuery(true)
-					->insert('#__associations');
+				$key   = md5(json_encode($associations) . $context);
 
 				foreach ($associations as $id)
 				{
-					$query->values(((int) $id) . ',' . $db->quote($this->associationsContext) . ',' . $db->quote($key));
-				}
+					$parentIdAndDateValues = DefaultAssocLangHelper::getParentValues(
+						$id, $dataId, $parentId, $parentModified, $assocParentDates, $old_key
+					);
+					$parentIdValue         = $parentIdAndDateValues[0];
+					$parentDateValue       = $parentIdAndDateValues[1] === 'NULL' ? 'NULL' : Factory::getDate($parentIdAndDateValues[1])->toSql();
+
+					$query = $db->getQuery(true)
+						->insert($db->quoteName('#__associations'));
 
-				$db->setQuery($query);
-				$db->execute();
+					// Save NULL for parent_date
+					if ($parentDateValue === 'NULL')
+					{
+						$query->values((' :id, :context, :key, :parentId, NULL'));
+					}
+					else
+					{
+						$query->values((' :id, :context, :key, :parentId, :parentDate'))
+							->bind(':parentDate', $parentDateValue);
+					}
+
+					$query->bind(':id', $id, ParameterType::INTEGER)
+						->bind(':context', $this->associationsContext)
+						->bind(':key', $key)
+						->bind(':parentId', $parentIdValue, ParameterType::INTEGER);
+
+					$db->setQuery($query);
+					$db->execute();
+				}
 			}
 		}
 
@@ -1647,6 +1686,20 @@ public function editAssociations($data)
 			}
 		}
 
+		$defaultAssocLang = Associations::getDefaultAssocLang();
+		$isParent = $data['language'] === $defaultAssocLang;
+
+		// If a default association language is set and the current item is a child item, then open his parent as reference and the child as target
+		if ($defaultAssocLang && !$isParent)
+		{
+			// If there is an associated parent, change reference id.
+			if ($data['associations'][$defaultAssocLang])
+			{
+				$id     = $data['associations'][$defaultAssocLang];
+				$target = '&target=' . $data['language'] . '%3A' . $data['id'] . '%3Aedit';
+			}
+		}
+
 		$app->redirect(
 			Route::_(
 				'index.php?option=com_associations&view=association&layout=edit&itemtype=' . $this->typeAlias
diff --git a/plugins/sampledata/multilang/multilang.php b/plugins/sampledata/multilang/multilang.php
index 11416a25f2bbb..958520651ce40 100644
--- a/plugins/sampledata/multilang/multilang.php
+++ b/plugins/sampledata/multilang/multilang.php
@@ -20,6 +20,7 @@
 use Joomla\CMS\Plugin\CMSPlugin;
 use Joomla\CMS\Table\Table;
 use Joomla\Database\Exception\ExecutionFailureException;
+use Joomla\Database\ParameterType;
 
 /**
  * Sampledata - Multilang Plugin
@@ -517,7 +518,9 @@ private function enablePlugin($pluginName)
 					. '"item_associations":"1",'
 					. '"remove_default_prefix":"0",'
 					. '"lang_cookie":"0",'
-					. '"alternate_meta":"1"'
+					. '"alternate_meta":"1",'
+					. '"use_default_assoc_lang":0,'
+					. '"default_assoc_lang":""'
 				. '}';
 			$query
 				->clear()
@@ -901,24 +904,29 @@ private function addAssociations($groupedAssociations)
 
 		foreach ($groupedAssociations as $context => $associations)
 		{
-			$key   = md5(json_encode($associations));
-			$query = $db->getQuery(true)
-				->insert('#__associations');
+			$key      = md5(json_encode($associations));
+			$parentId = -1;
 
 			foreach ($associations as $language => $id)
 			{
-				$query->values(((int) $id) . ',' . $db->quote($context) . ',' . $db->quote($key));
-			}
-
-			$db->setQuery($query);
-
-			try
-			{
-				$db->execute();
-			}
-			catch (\RuntimeException $e)
-			{
-				return false;
+				$query = $db->getQuery(true)
+					->insert($db->quoteName('#__associations'))
+					->values((' :id, :context, :key, :parentId, NULL'))
+					->bind(':id', $id, ParameterType::INTEGER)
+					->bind(':context', $context)
+					->bind(':key', $key)
+					->bind(':parentId', $parentId, ParameterType::INTEGER);
+
+				$db->setQuery($query);
+
+				try
+				{
+					$db->execute();
+				}
+				catch (\RuntimeException $e)
+				{
+					return false;
+				}
 			}
 		}
 
diff --git a/plugins/system/languagefilter/Field/ContentsitelanguageField.php b/plugins/system/languagefilter/Field/ContentsitelanguageField.php
new file mode 100644
index 0000000000000..0835815ee8a72
--- /dev/null
+++ b/plugins/system/languagefilter/Field/ContentsitelanguageField.php
@@ -0,0 +1,67 @@
+<?php
+/**
+ * @package     Joomla.Plugin
+ * @subpackage  System.languagefilter
+ *
+ * @copyright   Copyright (C) 2005 - 2019 Open Source Matters, Inc. All rights reserved.
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+namespace Joomla\Plugin\System\Languagefilter\Field;
+
+defined('_JEXEC') or die;
+
+use Joomla\CMS\Component\ComponentHelper;
+use Joomla\CMS\Form\Field\ContentlanguageField;
+use Joomla\CMS\HTML\HTMLHelper;
+use Joomla\CMS\Language\LanguageHelper;
+use Joomla\CMS\Language\Text;
+
+
+/**
+ * Content Site Languages Field class.
+ *
+ * @since  4.0
+ */
+class ContentsitelanguageField extends ContentlanguageField
+{
+	/**
+	 * The list field type.
+	 *
+	 * @var    string
+	 *
+	 * @since  4.0
+	 */
+	public $type = 'contentsitelanguage';
+
+	/**
+	 * Method to get the field options.
+	 *
+	 * @return  array The field option objects.
+	 *
+	 * @since   4.0
+	 */
+	public function getOptions()
+	{
+		$defaultSiteLanguage = ComponentHelper::getParams('com_languages')->get('site');
+		$contentLanguages = LanguageHelper::getContentLanguages(array(0, 1));
+		$options = array();
+
+		foreach ($contentLanguages as $langCode)
+		{
+			// Add the information to the language if it is the default site language
+			if ($langCode->lang_code == $defaultSiteLanguage)
+			{
+				$options[] = HTMLHelper::_('select.option', $langCode->lang_code, $langCode->title
+					. ' - ' . Text::_('PLG_SYSTEM_LANGUAGEFILTER_OPTION_DEFAULT_LANGUAGE')
+				);
+			}
+			else
+			{
+				$options[] = HTMLHelper::_('select.option', $langCode->lang_code, $langCode->title);
+			}
+		}
+
+		return $options;
+	}
+}
diff --git a/plugins/system/languagefilter/languagefilter.php b/plugins/system/languagefilter/languagefilter.php
index 7ef448fc93721..9612a92a13402 100644
--- a/plugins/system/languagefilter/languagefilter.php
+++ b/plugins/system/languagefilter/languagefilter.php
@@ -17,6 +17,7 @@
 use Joomla\CMS\Event\BeforeExecuteEvent;
 use Joomla\CMS\Factory;
 use Joomla\CMS\Filesystem\Folder;
+use Joomla\CMS\Helper\ContentHistoryHelper;
 use Joomla\CMS\Language\Associations;
 use Joomla\CMS\Language\Language;
 use Joomla\CMS\Language\LanguageHelper;
@@ -25,10 +26,14 @@
 use Joomla\CMS\Plugin\CMSPlugin;
 use Joomla\CMS\Router\Route;
 use Joomla\CMS\Router\Router;
+use Joomla\CMS\Table\Table;
 use Joomla\CMS\Uri\Uri;
+use Joomla\Component\Associations\Administrator\Helper\AssociationsHelper;
 use Joomla\Component\Menus\Administrator\Helper\MenusHelper;
+use Joomla\Database\ParameterType;
 use Joomla\Registry\Registry;
 use Joomla\String\StringHelper;
+use Joomla\Utilities\ArrayHelper;
 
 /**
  * Joomla! Language Filter Plugin.
@@ -960,4 +965,309 @@ private function getLanguageCookie()
 
 		return $languageCode;
 	}
+
+	// Events for Default Association Language:
+
+	/**
+	 * Before Saving extensions
+	 * Method is called when an extension is going to be saved.
+	 * Change parameters for default association language as they depends on other parameters.
+	 *
+	 * @param   string  $context  The extension
+	 * @param   JTable  $table    DataBase Table object
+	 *
+	 * @return  void
+	 *
+	 * @since   4.0.0
+	 */
+	public function onExtensionBeforeSave($context, $table)
+	{
+		if ($context !== 'com_plugins.plugin')
+		{
+			return true;
+		}
+
+		$tableElement = $table->element;
+
+		if ($tableElement !== 'languagefilter')
+		{
+			return true;
+		}
+
+		// Get the parameters which are to be saved.
+		$params          = json_decode($table->params);
+		$pluginStatus    = $table->enabled;
+		$itemAssocStatus = $params->item_associations ?? false;
+
+		// If the plugin and the parameter item_associations are enabled then set the correct value for the default association language.
+		if ($pluginStatus && $itemAssocStatus)
+		{
+			$params->default_assoc_lang = ($params->use_default_assoc_lang === 1)
+				? $params->default_assoc_lang
+				: '';
+		}
+		// Reset parameters for default association language
+		else
+		{
+			$params->use_default_assoc_lang = '';
+			$params->default_assoc_lang     = '';
+		}
+
+		// Check if there were changes for the default association language.
+		$this->hasAssocLangChanged = ($params->default_assoc_lang === $this->params->get('default_assoc_lang')) ? false : true;
+
+		return $table->params = json_encode($params);
+	}
+
+	/**
+	 * After save extensions
+	 * Method is called when an extension has been saved.
+	 *
+	 * @param   string  $context  The extension
+	 * @param   JTable  $table    DataBase Table object
+	 *
+	 * @return  void
+	 *
+	 * @since   4.0.0
+	 */
+	public function onExtensionAfterSave($context, $table)
+	{
+		if ($context !== 'com_plugins.plugin')
+		{
+			return true;
+		}
+
+		$tableElement = $table->element;
+
+		if ($tableElement !== 'languagefilter')
+		{
+			return true;
+		}
+
+		// Get the parameters which have been saved
+		$params = json_decode($table->params);
+
+		// Only set association parent items if the default association language has changed.
+		if ($this->hasAssocLangChanged)
+		{
+			$this->_setParentItem($params->default_assoc_lang);
+		}
+
+		unset($this->hasAssocLangChanged);
+	}
+
+	/**
+	 * Method to set the parent id and modified dates to all associated items.
+	 * This resets all current parent ids and modified dates and set these new.
+	 * Parent and children will be up-to-date, as they get the same modified date.
+	 *
+	 * @param   string  $language  The default association language
+	 *
+	 * @return  boolean  Returns true on success, false on failure.
+	 *
+	 * @throws  Exception
+	 *
+	 * @since   4.0.0
+	 */
+	private function _setParentItem($language)
+	{
+		$db               = Factory::getDbo();
+		$defaultAssocLang = $language;
+
+		// If there is no default association language set, set all parent ids to -1 and parent dates to null
+		if (!$defaultAssocLang)
+		{
+			$resetQuery = $db->getQuery(true)
+				->update($db->quoteName('#__associations'))
+				->set($db->quoteName('parent_id') . ' = -1')
+				->set($db->quoteName('parent_date') . ' = NULL');
+			$db->setQuery($resetQuery);
+
+			try
+			{
+				$db->execute();
+			}
+			catch (ExecutionFailureException $e)
+			{
+				return false;
+			}
+		}
+		else
+		{
+			// Get every different key
+			$keyQuery = $db->getQuery(true)
+				->select($db->quoteName('key'))
+				->from($db->quoteName('#__associations'))
+				->group($db->quoteName('key'))
+				->having('COUNT(*) > 1');
+			$assocKeys = $db->setQuery($keyQuery)->loadColumn();
+
+			foreach ($assocKeys as $value)
+			{
+				// Get the context of this association with the current key
+				$contextQuery = $db->getQuery(true)
+					->select($db->quoteName('context'))
+					->from($db->quoteName('#__associations'))
+					->where($db->quoteName('key') . ' = :key')
+					->bind(':key', $value);
+				$assocContext = $db->setQuery($contextQuery)->loadResult();
+
+				// Get the right table to search for modified date or save_date from history
+
+				$checkCategoryComponent = '';
+				$component = explode('.', $assocContext)[0];
+
+				if ($component === 'com_categories')
+				{
+					$fromTable              = $db->quoteName('#__categories', 'e');
+					$modified               = $db->quoteName('e.modified_time');
+					$checkCategoryComponent = $db->quoteName('e.extension');
+				}
+				else
+				{
+					$extension      = AssociationsHelper::getSupportedExtension($component);
+					$extensionType  = $extension['helper']->getItemTypes()[0];
+					$extensionTable = $extension['types'][$extensionType]->get('details')['tables'];
+					$tableName      = $extensionTable[array_keys($extensionTable)[0]];
+					$fromTable      = $db->quoteName($tableName, 'e');
+					$typeAlias      = $component . '.' . $extensionType;
+					$modified       = ($component === 'com_menus') ? '' : $db->quoteName('e.modified');
+				}
+
+				// Get ids of items with the default association language
+				$subQuery = $db->getQuery(true)
+					->select($db->quoteName('e.id'))
+					->from($fromTable)
+					->where($db->quoteName('e.language') . ' = :lang')
+					->bind(':lang', $defaultAssocLang);
+				$idResults = $db->setQuery($subQuery)->loadColumn();
+
+				// Get parent id of an item that has the default association language
+				$parentQuery = $db->getQuery(true)
+					->select($db->quoteName('id'))
+					->from($db->quoteName('#__associations'))
+					->whereIn($db->quoteName('id'), $idResults, ParameterType::INTEGER)
+					->where($db->quoteName('key') . ' = :key')
+					->bind(':key', $value);
+				$parentId = $db->setQuery($parentQuery)->loadResult();
+
+				// Get modified date of parent
+				if ($modified)
+				{
+					// Get the context of this category
+					if ($checkCategoryComponent)
+					{
+						$categoryQuery = $db->getQuery(true)
+							->select($checkCategoryComponent)
+							->from($fromTable)
+							->where($db->quoteName('id') . ' = :id')
+							->bind(':id', $parentId, ParameterType::INTEGER);
+						$categoryParentExtension = $db->setQuery($categoryQuery)->loadResult();
+						$typeAlias = $categoryParentExtension . '.category';
+					}
+
+					$component   = $categoryParentExtension ?? $component;
+					$saveHistory = ComponentHelper::getParams($component)->get('save_history', 0);
+
+					// If versions are enabled get the save_date of the parent item from history table otherwise use the modified date
+					if ($saveHistory)
+					{
+						$typeId        = Table::getInstance('ContentType')->getTypeId($typeAlias);
+						$parentHistory = ContentHistoryHelper::getHistory($typeId, $parentId);
+
+						// Latest saved date of the parent item
+						$parentModified = $parentHistory[0]->save_date;
+					}
+					else
+					{
+						$parentModQuery = $db->getQuery(true)
+							->select($modified)
+							->from($fromTable)
+							->where($db->quoteName('id') . ' = :id')
+							->bind(':id', $parentId, ParameterType::INTEGER);
+						$parentModified = $db->setQuery($parentModQuery)->loadResult();
+					}
+
+					$parentModifiedSql = Factory::getDate($parentModified)->toSql();
+				}
+
+				$parentId       = $parentId ?? -1;
+
+				// Set the id and the modified date of the parent item.
+				$query = $db->getQuery(true)
+					->update($db->quoteName('#__associations'))
+					->set($db->quoteName('parent_id') . ' = ' . $db->quote(0));
+
+				if ($modified)
+				{
+					$query->set($db->quoteName('parent_date') . ' = :parentDate')
+						->bind(':parentDate', $parentModifiedSql);
+				}
+				else
+				{
+					$query->set($db->quoteName('parent_date') . ' = NULL');
+				}
+
+				$query->where(
+					[
+						$db->quoteName('id') . ' = :id',
+						$db->quoteName('key') . ' = :key',
+						$db->quoteName('context') . ' = :context'
+					]
+				)
+					->bind(':id', $parentId, ParameterType::INTEGER)
+					->bind(':key', $value)
+					->bind(':context', $assocContext);
+				$db->setQuery($query);
+
+				try
+				{
+					$db->execute();
+				}
+				catch (ExecutionFailureException $e)
+				{
+					return false;
+				}
+
+				// Set the id and modified date of the parent item to the children
+				$query = $db->getQuery(true)
+					->update($db->quoteName('#__associations'))
+					->set($db->quoteName('parent_id') . ' = :parentId');
+
+				if ($modified)
+				{
+					$query->set($db->quoteName('parent_date') . ' = :parentDate')
+						->bind(':parentDate', $parentModifiedSql);
+				}
+				else
+				{
+					$query->set($db->quoteName('parent_date') . ' = NULL');
+				}
+
+				$query->where(
+					[
+						$db->quoteName('id') . ' <> :id',
+						$db->quoteName('key') . ' = :key',
+						$db->quoteName('context') . ' = :context'
+					]
+				)
+					->bind(':parentId', $parentId, ParameterType::INTEGER)
+					->bind(':id', $parentId, ParameterType::INTEGER)
+					->bind(':key', $value)
+					->bind(':context', $assocContext);
+				$db->setQuery($query);
+
+				try
+				{
+					$db->execute();
+				}
+				catch (ExecutionFailureException $e)
+				{
+					return false;
+				}
+			}
+		}
+
+		return true;
+	}
 }
diff --git a/plugins/system/languagefilter/languagefilter.xml b/plugins/system/languagefilter/languagefilter.xml
index fea021cbea836..c7aff4fbac573 100644
--- a/plugins/system/languagefilter/languagefilter.xml
+++ b/plugins/system/languagefilter/languagefilter.xml
@@ -9,8 +9,10 @@
 	<authorUrl>www.joomla.org</authorUrl>
 	<version>3.0.0</version>
 	<description>PLG_SYSTEM_LANGUAGEFILTER_XML_DESCRIPTION</description>
+	<namespace>Joomla\Plugin\System\Languagefilter</namespace>
 	<files>
 		<filename plugin="languagefilter">languagefilter.php</filename>
+		<folder>Field</folder>
 	</files>
 	<languages>
 		<language tag="en-GB">en-GB.plg_system_languagefilter.ini</language>
@@ -42,6 +44,11 @@
 					<option value="1">JYES</option>
 				</field>
 
+				<field
+						type="spacer"
+						hr="true"
+				/>
+
 				<field
 					name="item_associations"
 					type="radio"
@@ -54,6 +61,34 @@
 					<option value="1">JYES</option>
 				</field>
 
+				<field
+						name="use_default_assoc_lang"
+						type="radio"
+						label="PLG_SYSTEM_LANGUAGEFILTER_FIELD_USE_DEFAULT_ASSOC_LANG_LABEL"
+						description="PLG_SYSTEM_LANGUAGEFILTER_FIELD_USE_DEFAULT_ASSOC_LANG_DESC"
+						class="switcher"
+						default="0"
+						filter="integer"
+						showon="item_associations:1"
+					>
+					<option value="0">JNO</option>
+					<option value="1">JYES</option>
+				</field>
+
+				<field
+						name="default_assoc_lang"
+						type="contentsitelanguage"
+						label="PLG_SYSTEM_LANGUAGEFILTER_FIELD_DEFAULT_ASSOC_LANG_LABEL"
+						description="PLG_SYSTEM_LANGUAGEFILTER_FIELD_DEFAULT_ASSOC_LANG_DESC"
+						showon="item_associations:1[AND]use_default_assoc_lang:1"
+						addfieldprefix="Joomla\Plugin\System\Languagefilter\Field"
+				/>
+
+				<field
+						type="spacer"
+						hr="true"
+				/>
+
 				<field
 					name="alternate_meta"
 					type="radio"
@@ -114,4 +149,4 @@
 			</fieldset>
 		</fields>
 	</config>
-</extension>
\ No newline at end of file
+</extension>