diff --git a/framework/YiiBase.php b/framework/YiiBase.php
index 7d1ab98..b962c19 100644
--- a/framework/YiiBase.php
+++ b/framework/YiiBase.php
@@ -76,16 +76,16 @@ class YiiBase
 	/**
 	 * @var array initial property values that will be applied to objects newly created via [[createObject]].
 	 * The array keys are fully qualified namespaced class names, and the array values are the corresponding
-	 * name-value pairs for initializing the created class instances. Make sure the class names do NOT have
-	 * the leading backslashes. For example,
+	 * name-value pairs for initializing the created class instances. Please make sure class names are starting
+	 * with a backslash. For example,
 	 *
 	 * ~~~
 	 * array(
-	 *     'mycompany\foo\Bar' => array(
+	 *     '\Bar' => array(
 	 *         'prop1' => 'value1',
 	 *         'prop2' => 'value2',
 	 *     ),
-	 *     'mycompany\foo\Car' => array(
+	 *     '\mycompany\foo\Car' => array(
 	 *         'prop1' => 'value1',
 	 *         'prop2' => 'value2',
 	 *     ),
@@ -301,6 +301,9 @@ class YiiBase
 	/**
 	 * Creates a new object using the given configuration.
 	 *
+	 * The class of the object can be any class. It does not have to
+	 * extend from [[Object]] or [[Component]].
+	 *
 	 * The configuration can be either a string or an array.
 	 * If a string, it is treated as the *object type*; if an array,
 	 * it must contain a `class` element specifying the *object type*, and
@@ -310,7 +313,7 @@ class YiiBase
 	 * The object type can be either a class name or the [[getAlias|alias]] of
 	 * the class. For example,
 	 *
-	 * - `\app\components\GoogleMap`: namespaced class
+	 * - `\app\components\GoogleMap`: full qualified namespaced class.
 	 * - `@app/components/GoogleMap`: an alias
 	 *
 	 * This method does the following steps to create an object:
@@ -319,7 +322,7 @@ class YiiBase
 	 * - if [[objectConfig]] contains the configuration for the object class,
 	 *   it will be merged with the configuration passed to this method;
 	 * - initialize the object properties using the configuration passed to this method;
-	 * - call the `init` method of the object if it implements the [[yii\base\Initable]] interface.
+	 * - call the `init` method of the object if it implements the [[\yii\base\Initable]] interface.
 	 *
 	 * Below are some usage examples:
 	 *
@@ -337,6 +340,7 @@ class YiiBase
 	 * @param mixed $config the configuration. It can be either a string or an array.
 	 * @return mixed the created object
 	 * @throws \yii\base\Exception if the configuration is invalid.
+	 * @see \yii\base\Object::newInstance()
 	 */
 	public static function createObject($config)
 	{
@@ -372,9 +376,9 @@ class YiiBase
 			$object = $r->newInstanceArgs($args);
 		}
 
-		$c = get_class($object);
-		if (isset(\Yii::$objectConfig[$c])) {
-			$config = array_merge(\Yii::$objectConfig[$c], $config);
+		$class = '\\' . get_class($object);
+		if (isset(\Yii::$objectConfig[$class])) {
+			$config = array_merge(\Yii::$objectConfig[$class], $config);
 		}
 
 		foreach ($config as $name => $value) {
diff --git a/framework/base/Component.php b/framework/base/Component.php
index 1705904..8f1f660 100644
--- a/framework/base/Component.php
+++ b/framework/base/Component.php
@@ -461,11 +461,8 @@ class Component extends Object
 	 */
 	public function attachBehavior($name, $behavior)
 	{
-		if (!($behavior instanceof Behavior)) {
-			$behavior = \Yii::createObject($behavior);
-		}
-		$behavior->attach($this);
-		return $this->_b[$name] = $behavior;
+		$this->ensureBehaviors();
+		return $this->attachBehaviorInternal($name, $behavior);
 	}
 
 	/**
@@ -478,8 +475,9 @@ class Component extends Object
 	 */
 	public function attachBehaviors($behaviors)
 	{
+		$this->ensureBehaviors();
 		foreach ($behaviors as $name => $behavior) {
-			$this->attachBehavior($name, $behavior);
+			$this->attachBehaviorInternal($name, $behavior);
 		}
 	}
 
@@ -523,8 +521,23 @@ class Component extends Object
 		if ($this->_b === null) {
 			$this->_b = array();
 			foreach ($this->behaviors() as $name => $behavior) {
-				$this->attachBehavior($name, $behavior);
+				$this->attachBehaviorInternal($name, $behavior);
 			}
 		}
 	}
+
+	/**
+	 * Attaches a behavior to this component.
+	 * @param string $name the name of the behavior.
+	 * @param string|array|Behavior $behavior the behavior to be attached
+	 * @return Behavior the attached behavior.
+	 */
+	private function attachBehaviorInternal($name, $behavior)
+	{
+		if (!($behavior instanceof Behavior)) {
+			$behavior = \Yii::createObject($behavior);
+		}
+		$behavior->attach($this);
+		return $this->_b[$name] = $behavior;
+	}
 }
diff --git a/framework/base/Object.php b/framework/base/Object.php
index 5d4103b..af72f2a 100644
--- a/framework/base/Object.php
+++ b/framework/base/Object.php
@@ -300,8 +300,7 @@ class Object
 	 */
 	public static function newInstance($config = array())
 	{
-		$c = get_called_class();
-		$class = '\\' . $c;
+		$class = '\\' . get_called_class();
 
 		if (($n = func_num_args()-1) > 0) {
 			$args = func_get_args();
@@ -321,8 +320,8 @@ class Object
 			$object = $r->newInstanceArgs($args);
 		}
 
-		if (isset(\Yii::$objectConfig[$c])) {
-			$config = array_merge(\Yii::$objectConfig[$c], $config);
+		if (isset(\Yii::$objectConfig[$class])) {
+			$config = array_merge(\Yii::$objectConfig[$class], $config);
 		}
 
 		foreach ($config as $name => $value) {
diff --git a/framework/db/ar/ActiveQuery.php b/framework/db/ar/ActiveQuery.php
index 8d7caca..b1f0872 100644
--- a/framework/db/ar/ActiveQuery.php
+++ b/framework/db/ar/ActiveQuery.php
@@ -10,6 +10,9 @@
 
 namespace yii\db\ar;
 
+use yii\db\dao\BaseQuery;
+use yii\base\VectorIterator;
+
 /**
  * ActiveFinder.php is ...
  * todo: add SQL monitor
@@ -17,86 +20,72 @@ namespace yii\db\ar;
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-class ActiveQuery extends \yii\db\dao\BaseQuery implements \IteratorAggregate, \ArrayAccess, \Countable
+class ActiveQuery extends BaseQuery implements \IteratorAggregate, \ArrayAccess, \Countable
 {
 	public $modelClass;
 
 	public $with;
 	public $alias;
-	public $index;
+	public $indexBy;
+	public $asArray;
 
-	private $_count;
-	private $_sql;
-	private $_countSql;
-	private $_asArray;
-	private $_records;
+	public $records;
+	public $sql;
 
-	public function all()
+	public function all($refresh = false)
 	{
-		return $this->performQuery();
+		if ($this->records === null || $refresh) {
+			$this->records = $this->performQuery();
+		}
+		return $this->records;
 	}
 
-	public function one()
+	public function one($refresh = false)
 	{
-		$this->limit = 1;
-		$records = $this->performQuery();
-		if (isset($records[0])) {
-			$this->_count = 1;
-			return $records[0];
+		if ($this->records === null || $refresh) {
+			$this->limit = 1;
+			$this->records = $this->performQuery();
+		}
+		if (isset($this->records[0])) {
+			return $this->records[0];
 		} else {
-			$this->_count = 0;
 			return null;
 		}
 	}
 
 	public function asArray($value = true)
 	{
-		$this->_asArray = $value;
-	}
-
-	protected function performQuery()
-	{
-		$class = $this->modelClass;
-		$db = $class::getDbConnection();
-		$this->_sql = $this->getSql($db);
-		$command = $db->createCommand($this->_sql);
-		$command->bindValues($this->params);
-		$rows = $command->queryAll();
-		if ($this->_asArray) {
-			$records = $rows;
-		} else {
-			$records = array();
-			foreach ($rows as $row) {
-				$records[] = $class::populateRecord($row);
-			}
-		}
-		$this->_count = count($records);
-		return $records;
+		$this->asArray = $value;
+		return $this;
 	}
 
 	public function with()
 	{
-
+		$this->with = func_get_args();
+		return $this;
 	}
-//
-//	public function getSql($connection = null)
-//	{
-//
-//	}
 
-	public function setSql($value)
+	public function indexBy($column)
 	{
-		$this->_sql = $value;
+		$this->indexBy = $column;
+		return $this;
 	}
 
-	public function getCountSql()
+	public function alias($tableAlias)
 	{
-
+		$this->alias = $tableAlias;
+		return $this;
 	}
 
-	public function getOneSql()
+	/**
+	 * Returns the database connection used by this query.
+	 * This method returns the connection used by the [[modelClass]].
+	 * @return \yii\db\dao\Connection the database connection used by this query
+	 */
+	public function getDbConnection()
 	{
-
+		$class = $this->modelClass;
+		return $class::getDbConnection();
 	}
 
 	/**
@@ -105,23 +94,7 @@ class ActiveQuery extends \yii\db\dao\BaseQuery implements \IteratorAggregate, \
 	 */
 	public function getCount()
 	{
-		if ($this->_count !== null) {
-			return $this->_count;
-		} else {
-			return $this->_count = $this->performCountQuery();
-		}
-	}
-
-	protected function performCountQuery()
-	{
-		$select = $this->select;
-		$this->select = 'COUNT(*)';
-		$class = $this->modelClass;
-		$command = $this->createCommand($class::getDbConnection());
-		$this->_countSql = $command->getSql();
-		$count = $command->queryScalar();
-		$this->select = $select;
-		return $count;
+		return $this->count();
 	}
 
 	/**
@@ -137,7 +110,7 @@ class ActiveQuery extends \yii\db\dao\BaseQuery implements \IteratorAggregate, \
 	 */
 	public function cache($duration, $dependency = null, $queryCount = 1)
 	{
-		$this->connection->cache($duration, $dependency, $queryCount);
+		$this->getDbConnection()->cache($duration, $dependency, $queryCount);
 		return $this;
 	}
 
@@ -149,19 +122,30 @@ class ActiveQuery extends \yii\db\dao\BaseQuery implements \IteratorAggregate, \
 	 */
 	public function getIterator()
 	{
-		$records = $this->performQuery();
-		return new \yii\base\VectorIterator($records);
+		if ($this->records === null) {
+			$this->records = $this->performQuery();
+		}
+		return new VectorIterator($this->records);
 	}
 
 	/**
 	 * Returns the number of items in the vector.
 	 * This method is required by the SPL `Countable` interface.
 	 * It will be implicitly called when you use `count($vector)`.
+	 * @param boolean $bySql whether to get the count by performing a SQL COUNT query.
+	 * If this is false, it will count the number of records brought back by this query.
 	 * @return integer number of items in the vector.
 	 */
-	public function count()
+	public function count($bySql = false)
 	{
-		return $this->getCount();
+		if ($bySql) {
+			return $this->performCountQuery();
+		} else {
+			if ($this->records === null) {
+				$this->records = $this->performQuery();
+			}
+			return count($this->records);
+		}
 	}
 
 	/**
@@ -173,10 +157,10 @@ class ActiveQuery extends \yii\db\dao\BaseQuery implements \IteratorAggregate, \
 	 */
 	public function offsetExists($offset)
 	{
-		if ($this->_records === null) {
-			$this->_records = $this->performQuery();
+		if ($this->records === null) {
+			$this->records = $this->performQuery();
 		}
-		return isset($this->_records[$offset]);
+		return isset($this->records[$offset]);
 	}
 
 	/**
@@ -190,10 +174,10 @@ class ActiveQuery extends \yii\db\dao\BaseQuery implements \IteratorAggregate, \
 	 */
 	public function offsetGet($offset)
 	{
-		if ($this->_records === null) {
-			$this->_records = $this->performQuery();
+		if ($this->records === null) {
+			$this->records = $this->performQuery();
 		}
-		return isset($this->_records[$offset]) ? $this->_records[$offset] : null;
+		return isset($this->records[$offset]) ? $this->records[$offset] : null;
 	}
 
 	/**
@@ -209,10 +193,10 @@ class ActiveQuery extends \yii\db\dao\BaseQuery implements \IteratorAggregate, \
 	 */
 	public function offsetSet($offset, $item)
 	{
-		if ($this->_records === null) {
-			$this->_records = $this->performQuery();
+		if ($this->records === null) {
+			$this->records = $this->performQuery();
 		}
-		$this->_records[$offset] = $item;
+		$this->records[$offset] = $item;
 	}
 
 	/**
@@ -225,9 +209,38 @@ class ActiveQuery extends \yii\db\dao\BaseQuery implements \IteratorAggregate, \
 	 */
 	public function offsetUnset($offset)
 	{
-		if ($this->_records === null) {
-			$this->_records = $this->performQuery();
+		if ($this->records === null) {
+			$this->records = $this->performQuery();
+		}
+		unset($this->records[$offset]);
+	}
+
+	protected function performQuery()
+	{
+		$db = $this->getDbConnection();
+		$this->sql = $this->getSql($db);
+		$command = $db->createCommand($this->sql);
+		$command->bindValues($this->params);
+		$rows = $command->queryAll();
+		if ($this->asArray) {
+			$records = $rows;
+		} else {
+			$records = array();
+			$class = $this->modelClass;
+			foreach ($rows as $row) {
+				$records[] = $class::populateData($row);
+			}
 		}
-		unset($this->_records[$offset]);
+		return $records;
+	}
+
+	protected function performCountQuery()
+	{
+		$this->select = 'COUNT(*)';
+		$class = $this->modelClass;
+		$command = $this->createCommand($class::getDbConnection());
+		$this->sql = $command->getSql();
+		$count = $command->queryScalar();
+		return $count;
 	}
 }
diff --git a/framework/db/ar/ActiveRecord.php b/framework/db/ar/ActiveRecord.php
index e13a9c6..19f20ac 100644
--- a/framework/db/ar/ActiveRecord.php
+++ b/framework/db/ar/ActiveRecord.php
@@ -308,7 +308,7 @@ abstract class ActiveRecord extends \yii\base\Model
 	 */
 	public function __construct($scenario = 'insert')
 	{
-		if ($scenario === null) // internally used by populateRecord() and model()
+		if ($scenario === null) // internally used by populateData() and model()
 		{
 			return;
 		}
@@ -1186,7 +1186,7 @@ abstract class ActiveRecord extends \yii\base\Model
 	 * @return ActiveRecord the newly created active record. The class of the object is the same as the model class.
 	 * Null is returned if the input data is false.
 	 */
-	public static function populateRecord($row)
+	public static function populateData($row)
 	{
 		$record = static::instantiate($row);
 		$record->setScenario('update');
@@ -1204,7 +1204,7 @@ abstract class ActiveRecord extends \yii\base\Model
 
 	/**
 	 * Creates an active record instance.
-	 * This method is called by {@link populateRecord} and {@link populateRecords}.
+	 * This method is called by {@link populateData}.
 	 * You may override this method if the instance being created
 	 * depends the attributes that are to be populated to the record.
 	 * For example, by creating a record based on the value of a column,
diff --git a/framework/db/dao/BaseQuery.php b/framework/db/dao/BaseQuery.php
index 82a2431..d9b1520 100644
--- a/framework/db/dao/BaseQuery.php
+++ b/framework/db/dao/BaseQuery.php
@@ -11,12 +11,12 @@
 namespace yii\db\dao;
 
 /**
- * Query represents a SQL statement in a way that is independent of DBMS.
+ * BaseQuery represents a SQL statement in a way that is independent of DBMS.
  *
- * Query not only can represent a SELECT statement, it can also represent INSERT, UPDATE, DELETE,
+ * BaseQuery not only can represent a SELECT statement, it can also represent INSERT, UPDATE, DELETE,
  * and other commonly used DDL statements, such as CREATE TABLE, CREATE INDEX, etc.
  *
- * Query provides a set of methods to facilitate the specification of different clauses.
+ * BaseQuery provides a set of methods to facilitate the specification of different clauses.
  * These methods can be chained together. For example,
  *
  * ~~~
@@ -120,27 +120,36 @@ class BaseQuery extends \yii\base\Object
 	 * Columns can contain table prefixes (e.g. "tbl_user.id") and/or column aliases (e.g. "tbl_user.id AS user_id").
 	 * The method will automatically quote the column names unless a column contains some parenthesis
 	 * (which means the column contains a DB expression).
-	 * @param boolean $distinct whether to use 'SELECT DISTINCT'.
 	 * @param string $option additional option that should be appended to the 'SELECT' keyword. For example,
 	 * in MySQL, the option 'SQL_CALC_FOUND_ROWS' can be used.
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 */
-	public function select($columns = '*', $distinct = false, $option = '')
+	public function select($columns = '*', $option = '')
 	{
 		$this->select = $columns;
-		$this->distinct = $distinct;
 		$this->selectOption = $option;
 		return $this;
 	}
 
 	/**
+	 * Sets the value indicating whether to SELECT DISTINCT or not.
+	 * @param bool $value whether to SELECT DISTINCT or not.
+	 * @return BaseQuery the query object itself
+	 */
+	public function distinct($value = true)
+	{
+		$this->distinct = $value;
+		return $this;
+	}
+
+	/**
 	 * Sets the FROM part of the query.
 	 * @param mixed $tables the table(s) to be selected from. This can be either a string (e.g. 'tbl_user')
 	 * or an array (e.g. array('tbl_user', 'tbl_profile')) specifying one or several table names.
 	 * Table names can contain schema prefixes (e.g. 'public.tbl_user') and/or table aliases (e.g. 'tbl_user u').
 	 * The method will automatically quote the table names unless it contains some parenthesis
 	 * (which means the table is given as a sub-query or DB expression).
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 */
 	public function from($tables)
 	{
@@ -215,7 +224,7 @@ class BaseQuery extends \yii\base\Object
 	 * @param array $params the parameters (name=>value) to be bound to the query.
 	 * For anonymous parameters, they can alternatively be specified as separate parameters to this method.
 	 * For example, `where('type=? AND status=?', 100, 1)`.
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see andWhere()
 	 * @see orWhere()
 	 */
@@ -237,7 +246,7 @@ class BaseQuery extends \yii\base\Object
 	 * on how to specify this parameter.
 	 * @param array $params the parameters (name=>value) to be bound to the query.
 	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see where()
 	 * @see orWhere()
 	 */
@@ -263,7 +272,7 @@ class BaseQuery extends \yii\base\Object
 	 * on how to specify this parameter.
 	 * @param array $params the parameters (name=>value) to be bound to the query.
 	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see where()
 	 * @see andWhere()
 	 */
@@ -292,7 +301,7 @@ class BaseQuery extends \yii\base\Object
 	 * Please refer to [[where()]] on how to specify this parameter.
 	 * @param array $params the parameters (name=>value) to be bound to the query.
 	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 */
 	public function join($table, $condition, $params = array())
 	{
@@ -314,7 +323,7 @@ class BaseQuery extends \yii\base\Object
 	 * @param string|array $condition the join condition that should appear in the ON part.
 	 * Please refer to [[where()]] on how to specify this parameter.
 	 * @param array $params the parameters (name=>value) to be bound to the query
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 */
 	public function leftJoin($table, $condition, $params = array())
 	{
@@ -336,7 +345,7 @@ class BaseQuery extends \yii\base\Object
 	 * @param string|array $condition the join condition that should appear in the ON part.
 	 * Please refer to [[where()]] on how to specify this parameter.
 	 * @param array $params the parameters (name=>value) to be bound to the query
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 */
 	public function rightJoin($table, $condition, $params = array())
 	{
@@ -356,7 +365,7 @@ class BaseQuery extends \yii\base\Object
 	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
 	 * The method will automatically quote the table name unless it contains some parenthesis
 	 * (which means the table is given as a sub-query or DB expression).
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 */
 	public function crossJoin($table)
 	{
@@ -371,7 +380,7 @@ class BaseQuery extends \yii\base\Object
 	 * Table name can contain schema prefix (e.g. 'public.tbl_user') and/or table alias (e.g. 'tbl_user u').
 	 * The method will automatically quote the table name unless it contains some parenthesis
 	 * (which means the table is given as a sub-query or DB expression).
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 */
 	public function naturalJoin($table)
 	{
@@ -385,7 +394,7 @@ class BaseQuery extends \yii\base\Object
 	 * Columns can be specified in either a string (e.g. "id, name") or an array (e.g. array('id', 'name')).
 	 * The method will automatically quote the column names unless a column contains some parenthesis
 	 * (which means the column contains a DB expression).
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see addGroupBy()
 	 */
 	public function groupBy($columns)
@@ -400,7 +409,7 @@ class BaseQuery extends \yii\base\Object
 	 * Columns can be specified in either a string (e.g. "id, name") or an array (e.g. array('id', 'name')).
 	 * The method will automatically quote the column names unless a column contains some parenthesis
 	 * (which means the column contains a DB expression).
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see groupBy()
 	 */
 	public function addGroupBy($columns)
@@ -425,7 +434,7 @@ class BaseQuery extends \yii\base\Object
 	 * Please refer to [[where()]] on how to specify this parameter.
 	 * @param array $params the parameters (name=>value) to be bound to the query.
 	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see andHaving()
 	 * @see orHaving()
 	 */
@@ -447,7 +456,7 @@ class BaseQuery extends \yii\base\Object
 	 * on how to specify this parameter.
 	 * @param array $params the parameters (name=>value) to be bound to the query.
 	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see having()
 	 * @see orHaving()
 	 */
@@ -473,7 +482,7 @@ class BaseQuery extends \yii\base\Object
 	 * on how to specify this parameter.
 	 * @param array $params the parameters (name=>value) to be bound to the query.
 	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see having()
 	 * @see andHaving()
 	 */
@@ -498,7 +507,7 @@ class BaseQuery extends \yii\base\Object
 	 * Columns can be specified in either a string (e.g. "id ASC, name DESC") or an array (e.g. array('id ASC', 'name DESC')).
 	 * The method will automatically quote the column names unless a column contains some parenthesis
 	 * (which means the column contains a DB expression).
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see addOrderBy()
 	 */
 	public function orderBy($columns)
@@ -513,7 +522,7 @@ class BaseQuery extends \yii\base\Object
 	 * Columns can be specified in either a string (e.g. "id ASC, name DESC") or an array (e.g. array('id ASC', 'name DESC')).
 	 * The method will automatically quote the column names unless a column contains some parenthesis
 	 * (which means the column contains a DB expression).
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see orderBy()
 	 */
 	public function addOrderBy($columns)
@@ -535,7 +544,7 @@ class BaseQuery extends \yii\base\Object
 	/**
 	 * Sets the LIMIT part of the query.
 	 * @param integer $limit the limit
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 */
 	public function limit($limit)
 	{
@@ -546,7 +555,7 @@ class BaseQuery extends \yii\base\Object
 	/**
 	 * Sets the OFFSET part of the query.
 	 * @param integer $offset the offset
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 */
 	public function offset($offset)
 	{
@@ -557,7 +566,7 @@ class BaseQuery extends \yii\base\Object
 	/**
 	 * Appends a SQL statement using UNION operator.
 	 * @param string $sql the SQL statement to be appended using UNION
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 */
 	public function union($sql)
 	{
@@ -570,7 +579,7 @@ class BaseQuery extends \yii\base\Object
 	 * @param array list of query parameter values indexed by parameter placeholders.
 	 * For example, `array(':name'=>'Dan', ':age'=>31)`.
 	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see addParams()
 	 */
 	public function params($params)
@@ -584,7 +593,7 @@ class BaseQuery extends \yii\base\Object
 	 * @param array list of query parameter values indexed by parameter placeholders.
 	 * For example, `array(':name'=>'Dan', ':age'=>31)`.
 	 * Please refer to [[where()]] on alternative syntax of specifying anonymous parameters.
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 * @see params()
 	 */
 	public function addParams($params)
@@ -703,7 +712,7 @@ class BaseQuery extends \yii\base\Object
 
 	/**
 	 * Resets the query object to its original state.
-	 * @return Query the query object itself
+	 * @return BaseQuery the query object itself
 	 */
 	public function reset()
 	{
diff --git a/framework/db/dao/Query.php b/framework/db/dao/Query.php
index d48744e..a6c4322 100644
--- a/framework/db/dao/Query.php
+++ b/framework/db/dao/Query.php
@@ -43,7 +43,7 @@ class Query extends BaseQuery
 {
 	/**
 	 * @var array the operation that this query represents. This refers to the method call as well as
-	 * the corresponding parameters for constructing a non-query SQL statement (e.g. INSERT, CREATE TABLE).
+	 * the corresponding parameters for constructing a non-select SQL statement (e.g. INSERT, CREATE TABLE).
 	 * This property is mainly maintained by methods such as [[insert()]], [[update()]], [[createTable()]].
 	 * If this property is not set, it means this query represents a SELECT statement.
 	 */
diff --git a/upgrade.md b/upgrade.md
index d38beba..803be7c 100644
--- a/upgrade.md
+++ b/upgrade.md
@@ -31,6 +31,9 @@ Upgrading from v1.1.x
 - The root alias `@yii` now represents the framework installation directory.
    In 1.x, this is named as `system`. We also removed `zii` root alias.
 
+- Object serves as the base class that supports properties. And Component extends
+  from Object and supports events and behaviors. Behaviors declared in
+  Component::behaviors() are attached on demand.
 
 - `CList` is renamed to `Vector`, and `CMap` is renamed to `Dictionary`.
   Other collection classes are dropped in favor of SPL classes.