diff --git a/framework/YiiBase.php b/framework/YiiBase.php
index 61c80ae..5767e1f 100644
--- a/framework/YiiBase.php
+++ b/framework/YiiBase.php
@@ -189,10 +189,12 @@ class YiiBase
 
 	/**
 	 * Translates a path alias into an actual path.
+	 *
 	 * The path alias can be either a root alias registered via [[setAlias]] or an
 	 * alias starting with a root alias (e.g. `@yii/base/Component.php`).
 	 * In the latter case, the root alias will be replaced by the corresponding registered path
 	 * and the remaining part will be appended to it.
+	 *
 	 * Note, this method does not ensure the existence of the resulting path.
 	 * @param string $alias alias
 	 * @return mixed path corresponding to the alias, false if the root alias is not previously registered.
@@ -214,12 +216,20 @@ class YiiBase
 
 	/**
 	 * Registers a path alias.
+	 *
 	 * A path alias is a short name representing a path (a file path, a URL, etc.)
 	 * A path alias must start with '@' (e.g. '@yii').
+	 *
 	 * Note that this method neither checks the existence of the path nor normalizes the path.
+	 * Any trailing '/' and '\' characters in the path will be trimmed.
+	 *
 	 * @param string $alias alias to the path. The alias must start with '@'.
-	 * @param string $path the path corresponding to the alias. If this is null, the corresponding
-	 * path alias will be removed. The path can be a file path (e.g. `/tmp`) or a URL (e.g. `http://www.yiiframework.com`).
+	 * @param string $path the path corresponding to the alias. This can be
+	 *
+	 * - a directory or a file path (e.g. `/tmp`, `/tmp/main.txt`)
+	 * - a URL (e.g. `http://www.yiiframework.com`)
+	 * - a path alias (e.g. `@yii/base`). In this case, the path alias will be converted into the
+	 *   actual path first by calling [[getAlias]].
 	 * @see getAlias
 	 */
 	public static function setAlias($alias, $path)
@@ -227,9 +237,15 @@ class YiiBase
 		if ($path === null) {
 			unset(self::$aliases[$alias]);
 		}
-		else {
+		elseif ($path[0] !== '@') {
 			self::$aliases[$alias] = rtrim($path, '\\/');
 		}
+		elseif (($p = self::getAlias($path)) !== false) {
+			self::$aliases[$alias] = $p;
+		}
+		else {
+			throw new \yii\base\Exception('Invalid path: ' . $path);
+		}
 	}
 
 	/**
diff --git a/framework/base/Event.php b/framework/base/Event.php
index 33b2c86..abb46ec 100644
--- a/framework/base/Event.php
+++ b/framework/base/Event.php
@@ -16,7 +16,8 @@ namespace yii\base;
  * The [[sender]] property describes who raises the event.
  * And the [[handled]] property indicates if the event is handled.
  * If an event handler sets [[handled]] to be true, the rest of the
- * uninvoked handlers will be canceled.
+ * uninvoked handlers will no longer be called to handle the event.
+ * Additionally, an event may specify extra parameters via the [[params]] property.
  *
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
@@ -32,6 +33,10 @@ class Event extends Component
 	 * When a handler sets this to be true, the rest of the uninvoked event handlers will be canceled.
 	 */
 	public $handled = false;
+	/**
+	 * @var mixed extra parameters associated with the event.
+	 */
+	public $params;
 
 	/**
 	 * Constructor.
diff --git a/framework/base/Module.php b/framework/base/Module.php
index f6a408f..99ac5dc 100644
--- a/framework/base/Module.php
+++ b/framework/base/Module.php
@@ -21,17 +21,24 @@ namespace yii\base;
 abstract class Module extends Component
 {
 	/**
+	 * @var string the ID of this module. This should follow the same rule as naming PHP variables.
+	 */
+	public $id;
+	/**
+	 * @var array custom module parameters (name => value).
+	 */
+	public $params = array();
+	/**
 	 * @var array the IDs of the application components that should be preloaded.
 	 */
 	public $preload = array();
 	/**
 	 * @var array the behaviors that should be attached to the module.
-	 * The behaviors will be attached to the module when {@link init} is called.
-	 * Please refer to {@link CModel::behaviors} on how to specify the value of this property.
+	 * The behaviors will be attached to the module when [[init]] is called.
+	 * Please refer to [[Model::behaviors]] on how to specify the value of this property.
 	 */
 	public $behaviors = array();
 
-	private $_id;
 	private $_parentModule;
 	private $_basePath;
 	private $_modulePath;
@@ -104,32 +111,13 @@ abstract class Module extends Component
 	}
 
 	/**
-	 * Returns the module ID.
-	 * @return string the module ID.
-	 */
-	public function getId()
-	{
-		return $this->_id;
-	}
-
-	/**
-	 * Sets the module ID.
-	 * @param string $id the module ID
-	 */
-	public function setId($id)
-	{
-		$this->_id = $id;
-	}
-
-	/**
 	 * Returns the root directory of the module.
 	 * @return string the root directory of the module. Defaults to the directory containing the module class.
 	 */
 	public function getBasePath()
 	{
-		if ($this->_basePath === null)
-		{
-			$class = new ReflectionClass(get_class($this));
+		if ($this->_basePath === null) {
+			$class = new ReflectionClass($this);
 			$this->_basePath = dirname($class->getFileName());
 		}
 		return $this->_basePath;
@@ -139,74 +127,51 @@ abstract class Module extends Component
 	 * Sets the root directory of the module.
 	 * This method can only be invoked at the beginning of the constructor.
 	 * @param string $path the root directory of the module.
-	 * @throws CException if the directory does not exist.
+	 * @throws Exception if the directory does not exist.
 	 */
 	public function setBasePath($path)
 	{
-		if (($this->_basePath = realpath($path)) === false || !is_dir($this->_basePath))
-			throw new CException(Yii::t('yii', 'Base path "{path}" is not a valid directory.',
-				array('{path}' => $path)));
-	}
-
-	/**
-	 * Returns user-defined parameters.
-	 * @return CAttributeCollection the list of user-defined parameters
-	 */
-	public function getParams()
-	{
-		if ($this->_params !== null)
-			return $this->_params;
-		else
-		{
-			$this->_params = new CAttributeCollection;
-			$this->_params->caseSensitive = true;
-			return $this->_params;
+		if (($this->_basePath = realpath($path)) === false || !is_dir($this->_basePath)) {
+			throw new Exception('Invalid base path: ' . $path);
 		}
 	}
 
 	/**
-	 * Sets user-defined parameters.
-	 * @param array $value user-defined parameters. This should be in name-value pairs.
-	 */
-	public function setParams($value)
-	{
-		$params = $this->getParams();
-		foreach ($value as $k => $v)
-			$params->add($k, $v);
-	}
-
-	/**
-	 * Returns the directory that contains the application modules.
-	 * @return string the directory that contains the application modules. Defaults to the 'modules' subdirectory of {@link basePath}.
+	 * Returns the directory that contains child modules.
+	 * @return string the directory that contains child modules. Defaults to the `modules` subdirectory under [[basePath]].
 	 */
 	public function getModulePath()
 	{
-		if ($this->_modulePath !== null)
+		if ($this->_modulePath !== null) {
 			return $this->_modulePath;
-		else
+		}
+		else {
 			return $this->_modulePath = $this->getBasePath() . DIRECTORY_SEPARATOR . 'modules';
+		}
 	}
 
 	/**
-	 * Sets the directory that contains the application modules.
-	 * @param string $value the directory that contains the application modules.
-	 * @throws CException if the directory is invalid
+	 * Sets the directory that contains child modules.
+	 * @param string $value the directory that contains child modules.
+	 * @throws Exception if the directory is invalid
 	 */
 	public function setModulePath($value)
 	{
-		if (($this->_modulePath = realpath($value)) === false || !is_dir($this->_modulePath))
-			throw new CException(Yii::t('yii', 'The module path "{path}" is not a valid directory.',
-				array('{path}' => $value)));
+		if (($this->_modulePath = realpath($value)) === false || !is_dir($this->_modulePath)) {
+			throw new Exception('Invalid module path: ' . $value);
+		}
 	}
 
 	/**
-	 * Sets the aliases that are used in the module.
-	 * @param array $aliases list of aliases to be imported
+	 * Imports the specified path aliases.
+	 * This method is provided so that you can import a set of path aliases by module configuration.
+	 * @param array $aliases list of path aliases to be imported
 	 */
 	public function setImport($aliases)
 	{
-		foreach ($aliases as $alias)
-			Yii::import($alias);
+		foreach ($aliases as $alias) {
+			\Yii::import($alias);
+		}
 	}
 
 	/**