diff --git a/lib/private/activitymanager.php b/lib/private/activitymanager.php
index 66aa039eb18b5eb7375636513d51cfe1d1834481..f31b121c8e82f1b82528ee2315f52def3d9e9c9d 100755
--- a/lib/private/activitymanager.php
+++ b/lib/private/activitymanager.php
@@ -10,12 +10,21 @@ namespace OC;
 
 
 use OCP\Activity\IConsumer;
+use OCP\Activity\IExtension;
 use OCP\Activity\IManager;
 
 class ActivityManager implements IManager {
 
+	/**
+	 * @var \Closure[]
+	 */
 	private $consumers = array();
 
+	/**
+	 * @var \Closure[]
+	 */
+	private $extensions = array();
+
 	/**
 	 * @param $app
 	 * @param $subject
@@ -65,4 +74,189 @@ class ActivityManager implements IManager {
 		array_push($this->consumers, $callable);
 	}
 
+	/**
+	 * In order to improve lazy loading a closure can be registered which will be called in case
+	 * activity consumers are actually requested
+	 *
+	 * $callable has to return an instance of OCA\Activity\IConsumer
+	 *
+	 * @param \Closure $callable
+	 * @return void
+	 */
+	function registerExtension(\Closure $callable) {
+		array_push($this->extensions, $callable);
+	}
+
+	/**
+	 * Will return additional notification types as specified by other apps
+	 *
+	 * @param string $languageCode
+	 * @return array
+	 */
+	function getNotificationTypes($languageCode) {
+		$notificationTypes = array();
+		foreach($this->extensions as $extension) {
+			$c = $extension();
+			if ($c instanceof IExtension) {
+				$result = $c->getNotificationTypes($languageCode);
+				if (is_array($result)) {
+					$notificationTypes = array_merge($notificationTypes, $result);
+				}
+			}
+		}
+
+		return $notificationTypes;
+	}
+
+	/**
+	 * @param array $types
+	 * @param string $filter
+	 * @return array
+	 */
+	function filterNotificationTypes($types, $filter) {
+		foreach($this->extensions as $extension) {
+			$c = $extension();
+			if ($c instanceof IExtension) {
+				$result = $c->filterNotificationTypes($types, $filter);
+				if (is_array($result)) {
+					$types = $result;
+				}
+			}
+		}
+		return $types;
+	}
+
+	/**
+	 * @param string $method
+	 * @return array
+	 */
+	function getDefaultTypes($method) {
+		$defaultTypes = array();
+		foreach($this->extensions as $extension) {
+			$c = $extension();
+			if ($c instanceof IExtension) {
+				$types = $c->getDefaultTypes($method);
+				if (is_array($types)) {
+					$defaultTypes = array_merge($types, $defaultTypes);
+				}
+			}
+		}
+		return $defaultTypes;
+	}
+
+	/**
+	 * @param string $app
+	 * @param string $text
+	 * @param array $params
+	 * @param boolean $stripPath
+	 * @param boolean $highlightParams
+	 * @param string $languageCode
+	 * @return string|false
+	 */
+	function translate($app, $text, $params, $stripPath, $highlightParams, $languageCode) {
+		foreach($this->extensions as $extension) {
+			$c = $extension();
+			if ($c instanceof IExtension) {
+				$translation = $c->translate($app, $text, $params, $stripPath, $highlightParams, $languageCode);
+				if (is_string($translation)) {
+					return $translation;
+				}
+			}
+		}
+
+		return false;
+	}
+
+	/**
+	 * @param string $type
+	 * @return string
+	 */
+	function getTypeIcon($type) {
+		foreach($this->extensions as $extension) {
+			$c = $extension();
+			if ($c instanceof IExtension) {
+				$icon = $c->getTypeIcon($type);
+				if (is_string($icon)) {
+					return $icon;
+				}
+			}
+		}
+
+		return '';
+	}
+
+	/**
+	 * @param array $activity
+	 * @return integer|false
+	 */
+	function getGroupParameter($activity) {
+		foreach($this->extensions as $extension) {
+			$c = $extension();
+			if ($c instanceof IExtension) {
+				$parameter = $c->getGroupParameter($activity);
+				if ($parameter !== false) {
+					return $parameter;
+				}
+			}
+		}
+
+		return false;
+	}
+
+	/**
+	 * @return array
+	 */
+	function getNavigation() {
+		$entries = array(
+			'apps' => array(),
+			'top' => array(),
+		);
+		foreach($this->extensions as $extension) {
+			$c = $extension();
+			if ($c instanceof IExtension) {
+				$additionalEntries = $c->getNavigation();
+				if (is_array($additionalEntries)) {
+					$entries['apps'] = array_merge($entries['apps'], $additionalEntries['apps']);
+					$entries['top'] = array_merge($entries['top'], $additionalEntries['top']);
+				}
+			}
+		}
+
+		return $entries;
+	}
+
+	/**
+	 * @param string $filterValue
+	 * @return boolean
+	 */
+	function isFilterValid($filterValue) {
+		foreach($this->extensions as $extension) {
+			$c = $extension();
+			if ($c instanceof IExtension) {
+				if ($c->isFilterValid($filterValue) === true) {
+					return true;
+				}
+			}
+		}
+
+		return false;
+	}
+
+	/**
+	 * @param string $filter
+	 * @return array
+	 */
+	function getQueryForFilter($filter) {
+		foreach($this->extensions as $extension) {
+			$c = $extension();
+			if ($c instanceof IExtension) {
+				$result = $c->getQueryForFilter($filter);
+				if (is_array($result)) {
+					return $result;
+				}
+			}
+		}
+
+		return array(null, null);
+	}
 }
diff --git a/lib/private/l10n.php b/lib/private/l10n.php
index 3e44be881500378d8997d6da0a171d10b67a32b6..28b35e92a2f74316b482f84c2ce14b1ca21152f6 100644
--- a/lib/private/l10n.php
+++ b/lib/private/l10n.php
@@ -404,14 +404,15 @@ class OC_L10N implements \OCP\IL10N {
 
 	/**
 	 * find the best language
+	 *
 	 * @param array|string $app details below
-	 * string language
 	 *
 	 * If $app is an array, ownCloud assumes that these are the available
 	 * languages. Otherwise ownCloud tries to find the files in the l10n
 	 * folder.
 	 *
 	 * If nothing works it returns 'en'
+	 * @return string language
 	 */
 	public function getLanguageCode($app=null) {
 		return self::findLanguage($app);
diff --git a/lib/public/activity/iextension.php b/lib/public/activity/iextension.php
new file mode 100644
index 0000000000000000000000000000000000000000..6bb403a88966c3a5584f2a1a8b66325749cc60bb
--- /dev/null
+++ b/lib/public/activity/iextension.php
@@ -0,0 +1,120 @@
+<?php
+/**
+ * ownCloud
+ *
+ * @author Thomas Müller
+ * @copyright 2014 Thomas Müller deepdiver@owncloud.com
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU AFFERO GENERAL PUBLIC LICENSE for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public
+ * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/**
+ * Public interface of ownCloud for apps to use.
+ * Activity/IExtension interface
+ */
+
+// use OCP namespace for all classes that are considered public.
+// This means that they should be used by apps instead of the internal ownCloud classes
+namespace OCP\Activity;
+
+interface IExtension {
+	/**
+	 * The extension can return an array of additional notification types.
+	 * If no additional types are to be added false is to be returned
+	 *
+	 * @param string $languageCode
+	 * @return array|false
+	 */
+	public function getNotificationTypes($languageCode);
+
+	/**
+	 * The extension can filter the types based on the filter if required.
+	 * In case no filter is to be applied false is to be returned unchanged.
+	 *
+	 * @param array $types
+	 * @param string $filter
+	 * @return array|false
+	 */
+	public function filterNotificationTypes($types, $filter);
+
+	/**
+	 * For a given method additional types to be displayed in the settings can be returned.
+	 * In case no additional types are to be added false is to be returned.
+	 *
+	 * @param string $method
+	 * @return array|false
+	 */
+	public function getDefaultTypes($method);
+
+	/**
+	 * The extension can translate a given message to the requested languages.
+	 * If no translation is available false is to be returned.
+	 *
+	 * @param string $app
+	 * @param string $text
+	 * @param array $params
+	 * @param boolean $stripPath
+	 * @param boolean $highlightParams
+	 * @param string $languageCode
+	 * @return string|false
+	 */
+	public function translate($app, $text, $params, $stripPath, $highlightParams, $languageCode);
+
+	/**
+	 * A string naming the css class for the icon to be used can be returned.
+	 * If no icon is known for the given type false is to be returned.
+	 *
+	 * @param string $type
+	 * @return string|false
+	 */
+	public function getTypeIcon($type);
+
+	/**
+	 * The extension can define the parameter grouping by returning the index as integer.
+	 * In case no grouping is required false is to be returned.
+	 *
+	 * @param array $activity
+	 * @return integer|false
+	 */
+	public function getGroupParameter($activity);
+
+	/**
+	 * The extension can define additional navigation entries. The array returned has to contain two keys 'top'
+	 * and 'apps' which hold arrays with the relevant entries.
+	 * If no further entries are to be added false is no be returned.
+	 *
+	 * @return array|false
+	 */
+	public function getNavigation();
+
+	/**
+	 * The extension can check if a customer filter (given by a query string like filter=abc) is valid or not.
+	 *
+	 * @param string $filterValue
+	 * @return boolean
+	 */
+	public function isFilterValid($filterValue);
+
+	/**
+	 * For a given filter the extension can specify the sql query conditions including parameters for that query.
+	 * In case the extension does not know the filter false is to be returned.
+	 * The query condition and the parameters are to be returned as array with two elements.
+	 * E.g. return array('`app` = ? and `message` like ?', array('mail', 'ownCloud%'));
+	 *
+	 * @param string $filter
+	 * @return array|false
+	 */
+	public function getQueryForFilter($filter);
+}
diff --git a/lib/public/activity/imanager.php b/lib/public/activity/imanager.php
index 449fdcc934dcfd4addd86ecd49fff21de0a2829a..0a49fdf499958b4d916ba0c7f1eaa5ba98e436a0 100644
--- a/lib/public/activity/imanager.php
+++ b/lib/public/activity/imanager.php
@@ -50,11 +50,81 @@ interface IManager {
 	 * In order to improve lazy loading a closure can be registered which will be called in case
 	 * activity consumers are actually requested
 	 *
-	 * $callable has to return an instance of OCA\Activity\IConsumer
+	 * $callable has to return an instance of \OCP\Activity\IConsumer
 	 *
 	 * @param \Closure $callable
 	 * @return void
 	 */
 	function registerConsumer(\Closure $callable);
 
+	/**
+	 * In order to improve lazy loading a closure can be registered which will be called in case
+	 * activity consumers are actually requested
+	 *
+	 * $callable has to return an instance of \OCP\Activity\IExtension
+	 *
+	 * @param \Closure $callable
+	 * @return void
+	 */
+	function registerExtension(\Closure $callable);
+
+	/**
+	 * Will return additional notification types as specified by other apps
+	 * @param string $languageCode
+	 * @return array
+	 */
+	function getNotificationTypes($languageCode);
+
+	/**
+	 * @param array $types
+	 * @param string $filter
+	 * @return array
+	 */
+	function filterNotificationTypes($types, $filter);
+
+	/**
+	 * @param string $method
+	 * @return array
+	 */
+	function getDefaultTypes($method);
+
+	/**
+	 * @param string $app
+	 * @param string $text
+	 * @param array $params
+	 * @param boolean $stripPath
+	 * @param boolean $highlightParams
+	 * @param string $languageCode
+	 * @return string|false
+	 */
+	function translate($app, $text, $params, $stripPath, $highlightParams, $languageCode);
+
+	/**
+	 * @param string $type
+	 * @return string
+	 */
+	function getTypeIcon($type);
+
+	/**
+	 * @param array $activity
+	 * @return integer|false
+	 */
+	function getGroupParameter($activity);
+
+	/**
+	 * @return array
+	 */
+	function getNavigation();
+
+	/**
+	 * @param string $filterValue
+	 * @return boolean
+	 */
+	function isFilterValid($filterValue);
+
+	/**
+	 * @param string $filter
+	 * @return array
+	 */
+	function getQueryForFilter($filter);
 }
diff --git a/tests/lib/activitymanager.php b/tests/lib/activitymanager.php
new file mode 100644
index 0000000000000000000000000000000000000000..f21b82c52c368ed1a6a7d62f7373cdce609fd829
--- /dev/null
+++ b/tests/lib/activitymanager.php
@@ -0,0 +1,202 @@
+<?php
+
+/**
+ * Copyright (c) 2014 Thomas Müller <deepdiver@owncloud.com>
+ * This file is licensed under the Affero General Public License version 3 or
+ * later.
+ * See the COPYING-README file.
+ *
+*/
+
+class Test_ActivityManager extends PHPUnit_Framework_TestCase {
+
+	/** @var \OC\ActivityManager */
+	private $activityManager;
+
+	public function setUp() {
+		$this->activityManager = new \OC\ActivityManager();
+		$this->activityManager->registerExtension(function() {
+			return new NoOpExtension();
+		});
+		$this->activityManager->registerExtension(function() {
+			return new SimpleExtension();
+		});
+	}
+
+	public function testNotificationTypes() {
+		$result = $this->activityManager->getNotificationTypes('en');
+		$this->assertTrue(is_array($result));
+		$this->assertEquals(2, sizeof($result));
+	}
+
+	public function testFilterNotificationTypes() {
+		$result = $this->activityManager->filterNotificationTypes(array('NT0', 'NT1', 'NT2', 'NT3'), 'FILTER1');
+		$this->assertTrue(is_array($result));
+		$this->assertEquals(3, sizeof($result));
+
+		$result = $this->activityManager->filterNotificationTypes(array('NT0', 'NT1', 'NT2', 'NT3'), 'FILTER2');
+		$this->assertTrue(is_array($result));
+		$this->assertEquals(4, sizeof($result));
+	}
+
+	public function testDefaultTypes() {
+		$result = $this->activityManager->getDefaultTypes('stream');
+		$this->assertTrue(is_array($result));
+		$this->assertEquals(1, sizeof($result));
+
+		$result = $this->activityManager->getDefaultTypes('email');
+		$this->assertTrue(is_array($result));
+		$this->assertEquals(0, sizeof($result));
+	}
+
+	public function testTranslate() {
+		$result = $this->activityManager->translate('APP0', '', '', array(), false, false, 'en');
+		$this->assertEquals('Stupid translation', $result);
+
+		$result = $this->activityManager->translate('APP1', '', '', array(), false, false, 'en');
+		$this->assertFalse($result);
+	}
+
+	public function testTypeIcon() {
+		$result = $this->activityManager->getTypeIcon('NT1');
+		$this->assertEquals('icon-nt-one', $result);
+
+		$result = $this->activityManager->getTypeIcon('NT2');
+		$this->assertEquals('', $result);
+	}
+
+	public function testGroupParameter() {
+		$result = $this->activityManager->getGroupParameter(array());
+		$this->assertEquals(5, $result);
+	}
+
+	public function testNavigation() {
+		$result = $this->activityManager->getNavigation();
+		$this->assertEquals(4, sizeof($result['apps']));
+		$this->assertEquals(2, sizeof($result['top']));
+	}
+
+	public function testIsFilterValid() {
+		$result = $this->activityManager->isFilterValid('fv01');
+		$this->assertTrue($result);
+
+		$result = $this->activityManager->isFilterValid('FV2');
+		$this->assertFalse($result);
+	}
+
+	public function testQueryForFilter() {
+		$result = $this->activityManager->getQueryForFilter('filter1');
+		$this->assertEquals(
+			array(
+				'`app` = ? and `message` like ?',
+				array('mail', 'ownCloud%')
+			), $result
+		);
+
+		$result = $this->activityManager->isFilterValid('filter2');
+		$this->assertFalse($result);
+	}
+}
+
+class SimpleExtension implements \OCP\Activity\IExtension {
+
+	public function getNotificationTypes($languageCode) {
+		return array('NT1', 'NT2');
+	}
+
+	public function filterNotificationTypes($types, $filter) {
+		if ($filter === 'FILTER1') {
+			unset($types[0]);
+		}
+		return $types;
+	}
+
+	public function getDefaultTypes($method) {
+		if ($method === 'stream') {
+			return array('DT0');
+		}
+
+		return array();
+	}
+
+	public function translate($app, $text, $params, $stripPath, $highlightParams, $languageCode) {
+		if ($app === 'APP0') {
+			return "Stupid translation";
+		}
+
+		return false;
+	}
+
+	public function getTypeIcon($type) {
+		if ($type === 'NT1') {
+			return 'icon-nt-one';
+		}
+		return '';
+	}
+
+	public function getGroupParameter($activity) {
+		return 5;
+	}
+
+	public function getNavigation() {
+		return array(
+			'apps' => array('nav1', 'nav2', 'nav3', 'nav4'),
+			'top'  => array('top1', 'top2')
+		);
+	}
+
+	public function isFilterValid($filterValue) {
+		if ($filterValue === 'fv01') {
+			return true;
+		}
+
+		return false;
+	}
+
+	public function getQueryForFilter($filter) {
+		if ($filter === 'filter1') {
+			return array('`app` = ? and `message` like ?', array('mail', 'ownCloud%'));
+		}
+
+		return false;
+	}
+}
+
+class NoOpExtension implements \OCP\Activity\IExtension {
+
+	public function getNotificationTypes($languageCode) {
+		return false;
+	}
+
+	public function filterNotificationTypes($types, $filter) {
+		return false;
+	}
+
+	public function getDefaultTypes($method) {
+		return false;
+	}
+
+	public function translate($app, $text, $params, $stripPath, $highlightParams, $languageCode) {
+		return false;
+	}
+
+	public function getTypeIcon($type) {
+		return false;
+	}
+
+	public function getGroupParameter($activity) {
+		return false;
+	}
+
+	public function getNavigation() {
+		return false;
+	}
+
+	public function isFilterValid($filterValue) {
+		return false;
+	}
+
+	public function getQueryForFilter($filter) {
+		return false;
+	}
+}