diff --git a/extensions/composer/yii/composer/InstallerPlugin.php b/extensions/composer/yii/composer/InstallerPlugin.php
index f6de6b2..519363d 100644
--- a/extensions/composer/yii/composer/InstallerPlugin.php
+++ b/extensions/composer/yii/composer/InstallerPlugin.php
@@ -26,5 +26,9 @@ class InstallerPlugin implements PluginInterface
 	{
 		$installer = new Installer($io, $composer);
 		$composer->getInstallationManager()->addInstaller($installer);
+		$file = rtrim($composer->getConfig()->get('vendor-dir'), '/') . '/yii-extensions.php';
+		if (!is_file($file)) {
+			file_put_contents($file, "<?php\nreturn array();\n");
+		}
 	}
 }
diff --git a/extensions/jui/composer.json b/extensions/jui/composer.json
index e228973..9e97866 100644
--- a/extensions/jui/composer.json
+++ b/extensions/jui/composer.json
@@ -2,7 +2,7 @@
 	"name": "yiisoft/yii2-jui",
 	"description": "The Jquery UI extension for the Yii framework",
 	"keywords": ["yii", "Jquery UI", "renderer"],
-	"type": "library",
+	"type": "yii-extension",
 	"license": "BSD-3-Clause",
 	"support": {
 		"issues": "https://github.com/yiisoft/yii2/issues?state=open",
@@ -17,5 +17,8 @@
 	},
 	"autoload": {
 		"psr-0": { "yii\\jui\\": "" }
+	},
+	"extra": {
+		"bootstrap": "yii\\jui\\Extension"
 	}
 }
diff --git a/extensions/mutex/composer.json b/extensions/mutex/composer.json
index 99adcdf..172b5b2 100644
--- a/extensions/mutex/composer.json
+++ b/extensions/mutex/composer.json
@@ -24,7 +24,4 @@
 	"autoload": {
 		"psr-0": { "yii\\mutex\\": "" }
 	},
-	"extra": {
-		"bootstrap": "yii\\mutex\\Extension"
-	}
 }
diff --git a/extensions/smarty/composer.json b/extensions/smarty/composer.json
index 333e76e..b2d89a8 100644
--- a/extensions/smarty/composer.json
+++ b/extensions/smarty/composer.json
@@ -2,7 +2,7 @@
 	"name": "yiisoft/yii2-smarty",
 	"description": "The Smarty integration for the Yii framework",
 	"keywords": ["yii", "smarty", "renderer"],
-	"type": "library",
+	"type": "yii-extension",
 	"license": "BSD-3-Clause",
 	"support": {
 		"issues": "https://github.com/yiisoft/yii2/issues?state=open",
diff --git a/extensions/twig/composer.json b/extensions/twig/composer.json
index ba21065..9ff0132 100644
--- a/extensions/twig/composer.json
+++ b/extensions/twig/composer.json
@@ -2,7 +2,7 @@
 	"name": "yiisoft/yii2-twig",
 	"description": "The Twig integration for the Yii framework",
 	"keywords": ["yii", "twig", "renderer"],
-	"type": "library",
+	"type": "yii-extension",
 	"license": "BSD-3-Clause",
 	"support": {
 		"issues": "https://github.com/yiisoft/yii2/issues?state=open",
diff --git a/framework/yii/base/Application.php b/framework/yii/base/Application.php
index d92b05c..2bd3455 100644
--- a/framework/yii/base/Application.php
+++ b/framework/yii/base/Application.php
@@ -109,6 +109,19 @@ abstract class Application extends Module
 	 * @var array the parameters supplied to the requested action.
 	 */
 	public $requestedParams;
+	/**
+	 * @var array list of installed Yii extensions. Each array element represents a single extension
+	 * with the following structure:
+	 *
+	 * ~~~
+	 * [
+	 *     'name' => 'extension name',
+	 *     'version' => 'version number',
+	 *     'bootstrap' => 'BootstrapClassName',
+	 * ]
+	 * ~~~
+	 */
+	public $extensions = array();
 
 	/**
 	 * @var string Used to reserve memory for fatal error handler.
diff --git a/framework/yii/base/Extension.php b/framework/yii/base/Extension.php
new file mode 100644
index 0000000..dac9552
--- /dev/null
+++ b/framework/yii/base/Extension.php
@@ -0,0 +1,19 @@
+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\base;
+
+/**
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class Extension
+{
+	public static function init()
+	{
+	}
+}