diff --git a/framework/db/Query.php b/framework/db/Query.php
index 1d0c109..2239f5d 100644
--- a/framework/db/Query.php
+++ b/framework/db/Query.php
@@ -35,9 +35,19 @@ namespace yii\db;
 class Query extends \yii\base\Component
 {
 	/**
-	 * @var string|array the columns being selected. This refers to the SELECT clause in a SQL
-	 * statement. It can be either a string (e.g. `'id, name'`) or an array (e.g. `array('id', 'name')`).
-	 * If not set, if means all columns.
+	 * Sort ascending
+	 * @see orderBy
+	 */
+	const SORT_ASC = false;
+	/**
+	 * Sort ascending
+	 * @see orderBy
+	 */
+	const SORT_DESC = true;
+
+	/**
+	 * @var array the columns being selected. For example, `array('id', 'name')`.
+	 * This is used to construct the SELECT clause in a SQL statement. If not set, if means selecting all columns.
 	 * @see select()
 	 */
 	public $select;
@@ -52,8 +62,8 @@ class Query extends \yii\base\Component
 	 */
 	public $distinct;
 	/**
-	 * @var string|array the table(s) to be selected from. This refers to the FROM clause in a SQL statement.
-	 * It can be either a string (e.g. `'tbl_user, tbl_post'`) or an array (e.g. `array('tbl_user', 'tbl_post')`).
+	 * @var array the table(s) to be selected from. For example, `array('tbl_user', 'tbl_post')`.
+	 * This is used to construct the FROM clause in a SQL statement.
 	 * @see from()
 	 */
 	public $from;
@@ -73,20 +83,33 @@ class Query extends \yii\base\Component
 	 */
 	public $offset;
 	/**
-	 * @var string|array how to sort the query results. This refers to the ORDER BY clause in a SQL statement.
-	 * It can be either a string (e.g. `'id ASC, name DESC'`) or an array (e.g. `array('id ASC', 'name DESC')`).
+	 * @var array how to sort the query results. This is used to construct the ORDER BY clause in a SQL statement.
+	 * The array keys are the columns to be sorted by, and the array values are the corresponding sort directions which
+	 * can be either [[Query::SORT_ASC]] or [[Query::SORT_DESC]]. The array may also contain [[Expression]] objects.
+	 * If that is the case, the expressions will be converted into strings without any change.
 	 */
 	public $orderBy;
 	/**
-	 * @var string|array how to group the query results. This refers to the GROUP BY clause in a SQL statement.
-	 * It can be either a string (e.g. `'company, department'`) or an array (e.g. `array('company', 'department')`).
+	 * @var array how to group the query results. For example, `array('company', 'department')`.
+	 * This is used to construct the GROUP BY clause in a SQL statement.
 	 */
 	public $groupBy;
 	/**
-	 * @var string|array how to join with other tables. This refers to the JOIN clause in a SQL statement.
-	 * It can be either a string (e.g. `'LEFT JOIN tbl_user ON tbl_user.id=author_id'`) or an array (e.g.
-	 * `array('LEFT JOIN tbl_user ON tbl_user.id=author_id', 'LEFT JOIN tbl_team ON tbl_team.id=team_id')`).
-	 * @see join()
+	 * @var array how to join with other tables. Each array element represents the specification
+	 * of one join which has the following structure:
+	 *
+	 * ~~~
+	 * array($joinType, $tableName, $joinCondition)
+	 * ~~~
+	 *
+	 * For example,
+	 *
+	 * ~~~
+	 * array(
+	 *     array('INNER JOIN', 'tbl_user', 'tbl_user.id = author_id'),
+	 *     array('LEFT JOIN', 'tbl_team', 'tbl_team.id = team_id'),
+	 * )
+	 * ~~~
 	 */
 	public $join;
 	/**
@@ -95,9 +118,8 @@ class Query extends \yii\base\Component
 	 */
 	public $having;
 	/**
-	 * @var string|Query[] the UNION clause(s) in a SQL statement. This can be either a string
-	 * representing a single UNION clause or an array representing multiple UNION clauses.
-	 * Each union clause can be a string or a `Query` object which refers to the SQL statement.
+	 * @var array this is used to construct the UNION clause(s) in a SQL statement.
+	 * Each array element can be either a string or a [[Query]] object representing a sub-query.
 	 */
 	public $union;
 	/**
@@ -134,6 +156,9 @@ class Query extends \yii\base\Component
 	 */
 	public function select($columns, $option = null)
 	{
+		if (!is_array($columns)) {
+			$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
+		}
 		$this->select = $columns;
 		$this->selectOption = $option;
 		return $this;
@@ -161,6 +186,9 @@ class Query extends \yii\base\Component
 	 */
 	public function from($tables)
 	{
+		if (!is_array($tables)) {
+			$tables = preg_split('/\s*,\s*/', trim($tables), -1, PREG_SPLIT_NO_EMPTY);
+		}
 		$this->from = $tables;
 		return $this;
 	}
@@ -360,10 +388,13 @@ class Query extends \yii\base\Component
 	 * The method will automatically quote the column names unless a column contains some parenthesis
 	 * (which means the column contains a DB expression).
 	 * @return Query the query object itself
-	 * @see addGroup()
+	 * @see addGroupBy()
 	 */
 	public function groupBy($columns)
 	{
+		if (!is_array($columns)) {
+			$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
+		}
 		$this->groupBy = $columns;
 		return $this;
 	}
@@ -375,19 +406,16 @@ class Query extends \yii\base\Component
 	 * The method will automatically quote the column names unless a column contains some parenthesis
 	 * (which means the column contains a DB expression).
 	 * @return Query the query object itself
-	 * @see group()
+	 * @see groupBy()
 	 */
-	public function addGroup($columns)
+	public function addGroupBy($columns)
 	{
-		if (empty($this->groupBy)) {
+		if (!is_array($columns)) {
+			$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
+		}
+		if ($this->groupBy === null) {
 			$this->groupBy = $columns;
 		} else {
-			if (!is_array($this->groupBy)) {
-				$this->groupBy = preg_split('/\s*,\s*/', trim($this->groupBy), -1, PREG_SPLIT_NO_EMPTY);
-			}
-			if (!is_array($columns)) {
-				$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
-			}
 			$this->groupBy = array_merge($this->groupBy, $columns);
 		}
 		return $this;
@@ -454,43 +482,58 @@ class Query extends \yii\base\Component
 	/**
 	 * Sets the ORDER BY part of the query.
 	 * @param string|array $columns the columns (and the directions) to be ordered by.
-	 * Columns can be specified in either a string (e.g. "id ASC, name DESC") or an array (e.g. array('id ASC', 'name DESC')).
+	 * Columns can be specified in either a string (e.g. "id ASC, name DESC") or an array
+	 * (e.g. `array('id' => Query::SORT_ASC ASC, 'name' => Query::SORT_DESC)`).
 	 * The method will automatically quote the column names unless a column contains some parenthesis
 	 * (which means the column contains a DB expression).
 	 * @return Query the query object itself
-	 * @see addOrder()
+	 * @see addOrderBy()
 	 */
 	public function orderBy($columns)
 	{
-		$this->orderBy = $columns;
+		$this->orderBy = $this->normalizeOrderBy($columns);
 		return $this;
 	}
 
 	/**
 	 * Adds additional ORDER BY columns to the query.
 	 * @param string|array $columns the columns (and the directions) to be ordered by.
-	 * Columns can be specified in either a string (e.g. "id ASC, name DESC") or an array (e.g. array('id ASC', 'name DESC')).
+	 * Columns can be specified in either a string (e.g. "id ASC, name DESC") or an array
+	 * (e.g. `array('id' => Query::SORT_ASC ASC, 'name' => Query::SORT_DESC)`).
 	 * The method will automatically quote the column names unless a column contains some parenthesis
 	 * (which means the column contains a DB expression).
 	 * @return Query the query object itself
-	 * @see order()
+	 * @see orderBy()
 	 */
 	public function addOrderBy($columns)
 	{
-		if (empty($this->orderBy)) {
+		$columns = $this->normalizeOrderBy($columns);
+		if ($this->orderBy === null) {
 			$this->orderBy = $columns;
 		} else {
-			if (!is_array($this->orderBy)) {
-				$this->orderBy = preg_split('/\s*,\s*/', trim($this->orderBy), -1, PREG_SPLIT_NO_EMPTY);
-			}
-			if (!is_array($columns)) {
-				$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
-			}
 			$this->orderBy = array_merge($this->orderBy, $columns);
 		}
 		return $this;
 	}
 
+	protected function normalizeOrderBy($columns)
+	{
+		if (is_array($columns)) {
+			return $columns;
+		} else {
+			$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
+			$result = array();
+			foreach ($columns as $column) {
+				if (preg_match('/^(.*?)\s+(asc|desc)$/i', $column, $matches)) {
+					$result[$matches[1]] = strcasecmp($matches[2], 'desc') ? self::SORT_ASC : self::SORT_DESC;
+				} else {
+					$result[$column] = self::SORT_ASC;
+				}
+			}
+			return $result;
+		}
+	}
+
 	/**
 	 * Sets the LIMIT part of the query.
 	 * @param integer $limit the limit
diff --git a/framework/db/QueryBuilder.php b/framework/db/QueryBuilder.php
index 850020b..75375cc 100644
--- a/framework/db/QueryBuilder.php
+++ b/framework/db/QueryBuilder.php
@@ -60,10 +60,10 @@ class QueryBuilder extends \yii\base\Object
 			$this->buildFrom($query->from),
 			$this->buildJoin($query->join),
 			$this->buildWhere($query->where),
-			$this->buildGroup($query->groupBy),
+			$this->buildGroupBy($query->groupBy),
 			$this->buildHaving($query->having),
 			$this->buildUnion($query->union),
-			$this->buildOrder($query->orderBy),
+			$this->buildOrderBy($query->orderBy),
 			$this->buildLimit($query->limit, $query->offset),
 		);
 		return implode($this->separator, array_filter($clauses));
@@ -673,7 +673,7 @@ class QueryBuilder extends \yii\base\Object
 	}
 
 	/**
-	 * @param string|array $columns
+	 * @param array $columns
 	 * @param boolean $distinct
 	 * @param string $selectOption
 	 * @return string the SELECT clause built from [[query]].
@@ -689,13 +689,6 @@ class QueryBuilder extends \yii\base\Object
 			return $select . ' *';
 		}
 
-		if (!is_array($columns)) {
-			if (strpos($columns, '(') !== false) {
-				return $select . ' ' . $columns;
-			} else {
-				$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
-			}
-		}
 		foreach ($columns as $i => $column) {
 			if (is_object($column)) {
 				$columns[$i] = (string)$column;
@@ -716,7 +709,7 @@ class QueryBuilder extends \yii\base\Object
 	}
 
 	/**
-	 * @param string|array $tables
+	 * @param array $tables
 	 * @return string the FROM clause built from [[query]].
 	 */
 	public function buildFrom($tables)
@@ -725,13 +718,6 @@ class QueryBuilder extends \yii\base\Object
 			return '';
 		}
 
-		if (!is_array($tables)) {
-			if (strpos($tables, '(') !== false) {
-				return 'FROM ' . $tables;
-			} else {
-				$tables = preg_split('/\s*,\s*/', trim($tables), -1, PREG_SPLIT_NO_EMPTY);
-			}
-		}
 		foreach ($tables as $i => $table) {
 			if (strpos($table, '(') === false) {
 				if (preg_match('/^(.*?)(?i:\s+as\s+|\s+)(.*)$/i', $table, $matches)) { // with alias
@@ -752,37 +738,36 @@ class QueryBuilder extends \yii\base\Object
 	/**
 	 * @param string|array $joins
 	 * @return string the JOIN clause built from [[query]].
+	 * @throws Exception if the $joins parameter is not in proper format
 	 */
 	public function buildJoin($joins)
 	{
 		if (empty($joins)) {
 			return '';
 		}
-		if (is_string($joins)) {
-			return $joins;
-		}
 
 		foreach ($joins as $i => $join) {
-			if (is_array($join)) { // 0:join type, 1:table name, 2:on-condition
-				if (isset($join[0], $join[1])) {
-					$table = $join[1];
-					if (strpos($table, '(') === false) {
-						if (preg_match('/^(.*?)(?i:\s+as\s+|\s+)(.*)$/', $table, $matches)) { // with alias
-							$table = $this->db->quoteTableName($matches[1]) . ' ' . $this->db->quoteTableName($matches[2]);
-						} else {
-							$table = $this->db->quoteTableName($table);
-						}
+			if (is_object($join)) {
+				$joins[$i] = (string)$join;
+			} elseif (is_array($join) && isset($join[0], $join[1])) {
+				// 0:join type, 1:table name, 2:on-condition
+				$table = $join[1];
+				if (strpos($table, '(') === false) {
+					if (preg_match('/^(.*?)(?i:\s+as\s+|\s+)(.*)$/', $table, $matches)) { // with alias
+						$table = $this->db->quoteTableName($matches[1]) . ' ' . $this->db->quoteTableName($matches[2]);
+					} else {
+						$table = $this->db->quoteTableName($table);
 					}
-					$joins[$i] = $join[0] . ' ' . $table;
-					if (isset($join[2])) {
-						$condition = $this->buildCondition($join[2]);
-						if ($condition !== '') {
-							$joins[$i] .= ' ON ' . $this->buildCondition($join[2]);
-						}
+				}
+				$joins[$i] = $join[0] . ' ' . $table;
+				if (isset($join[2])) {
+					$condition = $this->buildCondition($join[2]);
+					if ($condition !== '') {
+						$joins[$i] .= ' ON ' . $this->buildCondition($join[2]);
 					}
-				} else {
-					throw new Exception('A join clause must be specified as an array of at least two elements.');
 				}
+			} else {
+				throw new Exception('A join clause must be specified as an array of join type, join table, and optionally join condition.');
 			}
 		}
 
@@ -800,16 +785,12 @@ class QueryBuilder extends \yii\base\Object
 	}
 
 	/**
-	 * @param string|array $columns
+	 * @param array $columns
 	 * @return string the GROUP BY clause
 	 */
-	public function buildGroup($columns)
+	public function buildGroupBy($columns)
 	{
-		if (empty($columns)) {
-			return '';
-		} else {
-			return 'GROUP BY ' . $this->buildColumns($columns);
-		}
+		return empty($columns) ? '' : 'GROUP BY ' . $this->buildColumns($columns);
 	}
 
 	/**
@@ -823,36 +804,24 @@ class QueryBuilder extends \yii\base\Object
 	}
 
 	/**
-	 * @param string|array $columns
+	 * @param array $columns
 	 * @return string the ORDER BY clause built from [[query]].
 	 */
-	public function buildOrder($columns)
+	public function buildOrderBy($columns)
 	{
 		if (empty($columns)) {
 			return '';
 		}
-		if (!is_array($columns)) {
-			if (strpos($columns, '(') !== false) {
-				return 'ORDER BY ' . $columns;
+		$orders = array();
+		foreach ($columns as $name => $direction) {
+			if (is_object($direction)) {
+				$orders[] = (string)$direction;
 			} else {
-				$columns = preg_split('/\s*,\s*/', trim($columns), -1, PREG_SPLIT_NO_EMPTY);
-			}
-		}
-		foreach ($columns as $i => $column) {
-			if (is_object($column)) {
-				$columns[$i] = (string)$column;
-			} elseif (strpos($column, '(') === false) {
-				if (preg_match('/^(.*?)\s+(asc|desc)$/i', $column, $matches)) {
-					$columns[$i] = $this->db->quoteColumnName($matches[1]) . ' ' . $matches[2];
-				} else {
-					$columns[$i] = $this->db->quoteColumnName($column);
-				}
+				$orders[] = $this->db->quoteColumnName($name) . ($direction === Query::SORT_DESC ? ' DESC' : '');
 			}
 		}
-		if (is_array($columns)) {
-			$columns = implode(', ', $columns);
-		}
-		return 'ORDER BY ' . $columns;
+
+		return 'ORDER BY ' . implode(', ', $orders);
 	}
 
 	/**
@@ -873,7 +842,7 @@ class QueryBuilder extends \yii\base\Object
 	}
 
 	/**
-	 * @param string|array $unions
+	 * @param array $unions
 	 * @return string the UNION clause built from [[query]].
 	 */
 	public function buildUnion($unions)
@@ -881,9 +850,6 @@ class QueryBuilder extends \yii\base\Object
 		if (empty($unions)) {
 			return '';
 		}
-		if (!is_array($unions)) {
-			$unions = array($unions);
-		}
 		foreach ($unions as $i => $union) {
 			if ($union instanceof Query) {
 				$unions[$i] = $this->build($union);
diff --git a/framework/web/Pagination.php b/framework/web/Pagination.php
index 14685b4..84585d6 100644
--- a/framework/web/Pagination.php
+++ b/framework/web/Pagination.php
@@ -65,7 +65,8 @@ use Yii;
 class Pagination extends \yii\base\Object
 {
 	/**
-	 * @var string name of the GET variable storing the current page index. Defaults to 'page'.
+	 * @var string name of the parameter storing the current page index. Defaults to 'page'.
+	 * @see params
 	 */
 	public $pageVar = 'page';
 	/**
diff --git a/framework/web/Sort.php b/framework/web/Sort.php
index 0afcbec..85e9ce8 100644
--- a/framework/web/Sort.php
+++ b/framework/web/Sort.php
@@ -8,7 +8,6 @@
 namespace yii\web;
 
 use Yii;
-use yii\util\StringHelper;
 use yii\util\Html;
 
 /**
@@ -18,38 +17,24 @@ use yii\util\Html;
  * we can use Sort to represent the sorting information and generate
  * appropriate hyperlinks that can lead to sort actions.
  *
- * Sort is designed to be used together with {@link CActiveRecord}.
- * When creating a Sort instance, you need to specify {@link modelClass}.
- * You can use Sort to generate hyperlinks by calling {@link link}.
- * You can also use Sort to modify a {@link CDbCriteria} instance by calling {@link applyOrder} so that
- * it can cause the query results to be sorted according to the specified
- * attributes.
- *
- * In order to prevent SQL injection attacks, Sort ensures that only valid model attributes
- * can be sorted. This is determined based on {@link modelClass} and {@link attributes}.
- * When {@link attributes} is not set, all attributes belonging to {@link modelClass}
- * can be sorted. When {@link attributes} is set, only those attributes declared in the property
- * can be sorted.
- *
- * By configuring {@link attributes}, one can perform more complex sorts that may
- * consist of things like compound attributes (e.g. sort based on the combination of
- * first name and last name of users).
- *
- * The property {@link attributes} should be an array of key-value pairs, where the keys
- * represent the attribute names, while the values represent the virtual attribute definitions.
- * For more details, please check the documentation about {@link attributes}.
- *
- *  * Controller action:
+ * A typical usage example is as follows,
  *
  * ~~~
  * function actionIndex()
  * {
  *     $sort = new Sort(array(
- *         'attributes' => Article::attributes(),
+ *         'attributes' => array(
+ *             'age',
+ *             'name' => array(
+ *                 'asc' => array('last_name', 'first_name'),
+ *                 'desc' => array('last_name' => true, 'first_name' => true),
+ *             ),
+ *         ),
  *     ));
+ *
  *     $models = Article::find()
  *         ->where(array('status' => 1))
- *         ->orderBy($sort->orderBy)
+ *         ->orderBy($sort->orders)
  *         ->all();
  *
  *     $this->render('index', array(
@@ -62,21 +47,23 @@ use yii\util\Html;
  * View:
  *
  * ~~~
+ * // display links leading to sort actions
+ * echo $sort->link('name', 'Name') . ' | ' . $sort->link('age', 'Age');
+ *
  * foreach($models as $model) {
  *     // display $model here
  * }
- *
- * // display pagination
- * $this->widget('yii\web\widgets\LinkPager', array(
- *     'pages' => $pages,
- * ));
  * ~~~
  *
- * @property string $orderBy The order-by columns represented by this sort object.
- * This can be put in the ORDER BY clause of a SQL statement.
- * @property array $directions Sort directions indexed by attribute names.
- * The sort direction. Can be either Sort::SORT_ASC for ascending order or
- * Sort::SORT_DESC for descending order.
+ * In the above, we declare two [[attributes]] that support sorting: name and age.
+ * We pass the sort information to the Article query so that the query results are
+ * sorted by the orders specified by the Sort object. In the view, we show two hyperlinks
+ * that can lead to pages with the data sorted by the corresponding attributes.
+ *
+ * @property array $orders Sort directions indexed by column names. The sort direction
+ * can be either [[Sort::ASC]] for ascending order or [[Sort::DESC]] for descending order.
+ * @property array $attributeOrders Sort directions indexed by attribute names. The sort
+ * direction can be either [[Sort::ASC]] for ascending order or [[Sort::DESC]] for descending order.
  *
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
@@ -86,12 +73,12 @@ class Sort extends \yii\base\Object
 	/**
 	 * Sort ascending
 	 */
-	const SORT_ASC = false;
+	const ASC = false;
 
 	/**
 	 * Sort descending
 	 */
-	const SORT_DESC = true;
+	const DESC = true;
 
 	/**
 	 * @var boolean whether the sorting can be applied to multiple attributes simultaneously.
@@ -100,111 +87,66 @@ class Sort extends \yii\base\Object
 	public $enableMultiSort = false;
 
 	/**
-	 * @var array list of attributes that are allowed to be sorted.
-	 * For example, array('user_id','create_time') would specify that only 'user_id'
-	 * and 'create_time' of the model {@link modelClass} can be sorted.
-	 * By default, this property is an empty array, which means all attributes in
-	 * {@link modelClass} are allowed to be sorted.
-	 *
-	 * This property can also be used to specify complex sorting. To do so,
-	 * a virtual attribute can be declared in terms of a key-value pair in the array.
-	 * The key refers to the name of the virtual attribute that may appear in the sort request,
-	 * while the value specifies the definition of the virtual attribute.
+	 * @var array list of attributes that are allowed to be sorted. Its syntax can be
+	 * described using the following example:
 	 *
-	 * In the simple case, a key-value pair can be like <code>'user'=>'user_id'</code>
-	 * where 'user' is the name of the virtual attribute while 'user_id' means the virtual
-	 * attribute is the 'user_id' attribute in the {@link modelClass}.
-	 *
-	 * A more flexible way is to specify the key-value pair as
-	 * <pre>
-	 * 'user'=>array(
-	 *     'asc'=>'first_name, last_name',
-	 *     'desc'=>'first_name DESC, last_name DESC',
-	 *     'label'=>'Name'
-	 * )
-	 * </pre>
-	 * where 'user' is the name of the virtual attribute that specifies the full name of user
-	 * (a compound attribute consisting of first name and last name of user). In this case,
-	 * we have to use an array to define the virtual attribute with three elements: 'asc',
-	 * 'desc' and 'label'.
-	 *
-	 * The above approach can also be used to declare virtual attributes that consist of relational
-	 * attributes. For example,
-	 * <pre>
-	 * 'price'=>array(
-	 *     'asc'=>'item.price',
-	 *     'desc'=>'item.price DESC',
-	 *     'label'=>'Item Price'
+	 * ~~~
+	 * array(
+	 *     'age',
+	 *     'user' => array(
+	 *         'asc' => array('first_name' => Sort::ASC, 'last_name' => Sort::ASC),
+	 *         'desc' => array('first_name' => Sort::DESC, 'last_name' => Sort::DESC),
+	 *         'default' => 'desc',
+	 *     ),
 	 * )
-	 * </pre>
+	 * ~~~
 	 *
-	 * Note, the attribute name should not contain '-' or '.' characters because
-	 * they are used as {@link separators}.
+	 * In the above, two attributes are declared: "age" and "user". The "age" attribute is
+	 * a simple attribute which is equivalent to the following:
 	 *
-	 * Starting from version 1.1.3, an additional option named 'default' can be used in the virtual attribute
-	 * declaration. This option specifies whether an attribute should be sorted in ascending or descending
-	 * order upon user clicking the corresponding sort hyperlink if it is not currently sorted. The valid
-	 * option values include 'asc' (default) and 'desc'. For example,
-	 * <pre>
-	 * 'price'=>array(
-	 *     'asc'=>'item.price',
-	 *     'desc'=>'item.price DESC',
-	 *     'label'=>'Item Price',
-	 *     'default'=>'desc',
+	 * ~~~
+	 * 'age' => array(
+	 *     'asc' => array('age' => Sort::ASC),
+	 *     'desc' => array('age' => Sort::DESC),
 	 * )
-	 * </pre>
+	 * ~~~
 	 *
-	 * Also starting from version 1.1.3, you can include a star ('*') element in this property so that
-	 * all model attributes are available for sorting, in addition to those virtual attributes. For example,
-	 * <pre>
-	 * 'attributes'=>array(
-	 *     'price'=>array(
-	 *         'asc'=>'item.price',
-	 *         'desc'=>'item.price DESC',
-	 *         'label'=>'Item Price',
-	 *         'default'=>'desc',
-	 *     ),
-	 *     '*',
-	 * )
-	 * </pre>
-	 * Note that when a name appears as both a model attribute and a virtual attribute, the position of
-	 * the star element in the array determines which one takes precedence. In particular, if the star
-	 * element is the first element in the array, the model attribute takes precedence; and if the star
-	 * element is the last one, the virtual attribute takes precedence.
+	 * The "user" attribute is a composite attribute:
+	 *
+	 * - The "user" key represents the attribute name which will appear in the URLs leading
+	 *   to sort actions. Attribute names cannot contain characters listed in [[separators]].
+	 * - The "asc" and "desc" elements specify how to sort by the attribute in ascending
+	 *   and descending orders, respectively. Their values represent the actual columns and
+	 *   the directions by which the data should be sorted by.
+	 * - And the "default" element specifies if the attribute is not sorted currently,
+	 *   in which direction it should be sorted (the default value is ascending order).
 	 */
 	public $attributes = array();
 	/**
-	 * @var string the name of the GET parameter that specifies which attributes to be sorted
+	 * @var string the name of the parameter that specifies which attributes to be sorted
 	 * in which direction. Defaults to 'sort'.
+	 * @see params
 	 */
 	public $sortVar = 'sort';
 	/**
-	 * @var string the tag appeared in the GET parameter that indicates the attribute should be sorted
+	 * @var string the tag appeared in the [[sortVar]] parameter that indicates the attribute should be sorted
 	 * in descending order. Defaults to 'desc'.
 	 */
 	public $descTag = 'desc';
 	/**
-	 * @var mixed the default order that should be applied to the query criteria when
-	 * the current request does not specify any sort. For example, 'name, create_time DESC' or
-	 * 'UPPER(name)'.
+	 * @var array the order that should be used when the current request does not specify any order.
+	 * The array keys are attribute names and the array values are the corresponding sort directions. For example,
 	 *
-	 * Starting from version 1.1.3, you can also specify the default order using an array.
-	 * The array keys could be attribute names or virtual attribute names as declared in {@link attributes},
-	 * and the array values indicate whether the sorting of the corresponding attributes should
-	 * be in descending order. For example,
-	 * <pre>
-	 * 'defaultOrder'=>array(
-	 *     'price'=>Sort::SORT_DESC,
+	 * ~~~
+	 * array(
+	 *     'name' => Sort::ASC,
+	 *     'create_time' => Sort::DESC,
 	 * )
-	 * </pre>
-	 * `SORT_DESC` and `SORT_ASC` are available since 1.1.10. In earlier Yii versions you should use
-	 * `true` and `false` respectively.
+	 * ~~~
 	 *
-	 * Please note when using array to specify the default order, the corresponding attributes
-	 * will be put into {@link directions} and thus affect how the sort links are rendered
-	 * (e.g. an arrow may be displayed next to the currently active sort link).
+	 * @see attributeOrders
 	 */
-	public $defaultOrder;
+	public $defaults;
 	/**
 	 * @var string the route of the controller action for displaying the sorted contents.
 	 * If not set, it means using the currently requested route.
@@ -218,61 +160,52 @@ class Sort extends \yii\base\Object
 	 */
 	public $separators = array('-', '.');
 	/**
-	 * @var array parameters (name=>value) that should be used to obtain the current sort directions
+	 * @var array parameters (name => value) that should be used to obtain the current sort directions
 	 * and to create new sort URLs. If not set, $_GET will be used instead.
 	 *
 	 * The array element indexed by [[sortVar]] is considered to be the current sort directions.
-	 * If the element does not exist, the [[defaultOrder]] will be used.
+	 * If the element does not exist, the [[defaults|default order]] will be used.
+	 *
+	 * @see sortVar
+	 * @see defaults
 	 */
 	public $params;
 
-	private $_directions;
-
-
 	/**
-	 * @return string the order-by columns represented by this sort object.
-	 * This can be put in the ORDER BY clause of a SQL statement.
+	 * Returns the columns and their corresponding sort directions.
+	 * @return array the columns (keys) and their corresponding sort directions (values).
+	 * This can be passed to [[\yii\db\Query::orderBy()]] to construct a DB query.
 	 */
-	public function getOrderBy()
+	public function getOrders()
 	{
-		$directions = $this->getDirections();
-		if (empty($directions)) {
-			return is_string($this->defaultOrder) ? $this->defaultOrder : '';
-		} else {
-			$orders = array();
-			foreach ($directions as $attribute => $descending) {
-				$definition = $this->getDefinition($attribute);
-				if ($descending) {
-					$orders[] = isset($definition['desc']) ? $definition['desc'] : $attribute . ' DESC';
-				} else {
-					$orders[] = isset($definition['asc']) ? $definition['asc'] : $attribute;
-				}
+		$attributeOrders = $this->getAttributeOrders();
+		$orders = array();
+		foreach ($attributeOrders as $attribute => $direction) {
+			$definition = $this->getAttribute($attribute);
+			$columns = $definition[$direction === self::ASC ? 'asc' : 'desc'];
+			foreach ($columns as $name => $dir) {
+				$orders[$name] = $dir;
 			}
-			return implode(', ', $orders);
 		}
+		return $orders;
 	}
 
 	/**
-	 * Generates a hyperlink that can be clicked to cause sorting.
-	 * @param string $attribute the attribute name. This must be the actual attribute name, not alias.
-	 * If it is an attribute of a related AR object, the name should be prefixed with
-	 * the relation name (e.g. 'author.name', where 'author' is the relation name).
-	 * @param string $label the link label. If null, the label will be determined according
-	 * to the attribute (see {@link resolveLabel}).
+	 * Generates a hyperlink that links to the sort action to sort by the specified attribute.
+	 * Based on the sort direction, the CSS class of the generated hyperlink will be appended
+	 * with "asc" or "desc".
+	 * @param string $attribute the attribute name by which the data should be sorted by.
+	 * @param string $label the link label. Note that the label will not be HTML-encoded.
 	 * @param array $htmlOptions additional HTML attributes for the hyperlink tag
 	 * @return string the generated hyperlink
 	 */
-	public function link($attribute, $label = null, $htmlOptions = array())
+	public function link($attribute, $label, $htmlOptions = array())
 	{
-		if (($definition = $this->getDefinition($attribute)) === false) {
-			return false;
-		}
-
-		if ($label === null) {
-			$label = isset($definition['label']) ? $definition['label'] : StringHelper::camel2words($attribute);
+		if (($definition = $this->getAttribute($attribute)) === false) {
+			return $label;
 		}
 
-		if (($direction = $this->getDirection($attribute)) !== null) {
+		if (($direction = $this->getAttributeOrder($attribute)) !== null) {
 			$class = $direction ? 'desc' : 'asc';
 			if (isset($htmlOptions['class'])) {
 				$htmlOptions['class'] .= ' ' . $class;
@@ -286,17 +219,19 @@ class Sort extends \yii\base\Object
 		return Html::link($label, $url, $htmlOptions);
 	}
 
+	private $_attributeOrders;
+
 	/**
 	 * Returns the currently requested sort information.
 	 * @param boolean $recalculate whether to recalculate the sort directions
 	 * @return array sort directions indexed by attribute names.
-	 * Sort direction can be either Sort::SORT_ASC for ascending order or
-	 * Sort::SORT_DESC for descending order.
+	 * Sort direction can be either [[Sort::ASC]] for ascending order or
+	 * [[Sort::DESC]] for descending order.
 	 */
-	public function getDirections($recalculate = false)
+	public function getAttributeOrders($recalculate = false)
 	{
-		if ($this->_directions === null || $recalculate) {
-			$this->_directions = array();
+		if ($this->_attributeOrders === null || $recalculate) {
+			$this->_attributeOrders = array();
 			$params = $this->params === null ? $_GET : $this->params;
 			if (isset($params[$this->sortVar]) && is_scalar($params[$this->sortVar])) {
 				$attributes = explode($this->separators[0], $params[$this->sortVar]);
@@ -308,49 +243,50 @@ class Sort extends \yii\base\Object
 						}
 					}
 
-					if (($this->getDefinition($attribute)) !== false) {
-						$this->_directions[$attribute] = $descending;
+					if (($this->getAttribute($attribute)) !== false) {
+						$this->_attributeOrders[$attribute] = $descending;
 						if (!$this->enableMultiSort) {
-							return $this->_directions;
+							return $this->_attributeOrders;
 						}
 					}
 				}
 			}
-			if ($this->_directions === array() && is_array($this->defaultOrder)) {
-				$this->_directions = $this->defaultOrder;
+			if ($this->_attributeOrders === array() && is_array($this->defaults)) {
+				$this->_attributeOrders = $this->defaults;
 			}
 		}
-		return $this->_directions;
+		return $this->_attributeOrders;
 	}
 
 	/**
 	 * Returns the sort direction of the specified attribute in the current request.
 	 * @param string $attribute the attribute name
-	 * @return boolean|null Sort direction of the attribute. Can be either Sort::SORT_ASC
-	 * for ascending order or Sort::SORT_DESC for descending order. Value is null
-	 * if the attribute does not need to be sorted.
+	 * @return boolean|null Sort direction of the attribute. Can be either [[Sort::ASC]]
+	 * for ascending order or [[Sort::DESC]] for descending order. Null is returned
+	 * if the attribute is invalid or does not need to be sorted.
 	 */
-	public function getDirection($attribute)
+	public function getAttributeOrder($attribute)
 	{
-		$this->getDirections();
-		return isset($this->_directions[$attribute]) ? $this->_directions[$attribute] : null;
+		$this->getAttributeOrders();
+		return isset($this->_attributeOrders[$attribute]) ? $this->_attributeOrders[$attribute] : null;
 	}
 
 	/**
 	 * Creates a URL for sorting the data by the specified attribute.
-	 * This method will consider the current sorting status given by [[directions]].
+	 * This method will consider the current sorting status given by [[attributeOrders]].
 	 * For example, if the current page already sorts the data by the specified attribute in ascending order,
 	 * then the URL created will lead to a page that sorts the data by the specified attribute in descending order.
 	 * @param string $attribute the attribute name
 	 * @return string|boolean the URL for sorting. False if the attribute is invalid.
+	 * @see attributeOrders
 	 * @see params
 	 */
 	public function createUrl($attribute)
 	{
-		if (($definition = $this->getDefinition($attribute)) === false) {
+		if (($definition = $this->getAttribute($attribute)) === false) {
 			return false;
 		}
-		$directions = $this->getDirections();
+		$directions = $this->getAttributeOrders();
 		if (isset($directions[$attribute])) {
 			$descending = !$directions[$attribute];
 			unset($directions[$attribute]);
@@ -378,28 +314,20 @@ class Sort extends \yii\base\Object
 	}
 
 	/**
-	 * Returns the real definition of an attribute given its name.
-	 *
-	 * The resolution is based on {@link attributes} and {@link CActiveRecord::attributeNames}.
-	 * <ul>
-	 * <li>When {@link attributes} is an empty array, if the name refers to an attribute of {@link modelClass},
-	 * then the name is returned back.</li>
-	 * <li>When {@link attributes} is not empty, if the name refers to an attribute declared in {@link attributes},
-	 * then the corresponding virtual attribute definition is returned. Starting from version 1.1.3, if {@link attributes}
-	 * contains a star ('*') element, the name will also be used to match against all model attributes.</li>
-	 * <li>In all other cases, false is returned, meaning the name does not refer to a valid attribute.</li>
-	 * </ul>
-	 * @param string $attribute the attribute name that the user requests to sort on
-	 * @return mixed the attribute name or the virtual attribute definition. False if the attribute cannot be sorted.
+	 * Returns the attribute definition of the specified name.
+	 * @param string $name the attribute name
+	 * @return array|boolean the sort definition (column names => sort directions).
+	 * False is returned if the attribute cannot be sorted.
+	 * @see attributes
 	 */
-	public function getDefinition($attribute)
+	public function getAttribute($name)
 	{
-		if (isset($this->attributes[$attribute])) {
-			return $this->attributes[$attribute];
-		} elseif (in_array($attribute, $this->attributes, true)) {
+		if (isset($this->attributes[$name])) {
+			return $this->attributes[$name];
+		} elseif (in_array($name, $this->attributes, true)) {
 			return array(
-				'asc' => $attribute,
-				'desc' => "$attribute DESC",
+				'asc' => array($name => self::ASC),
+				'desc' => array($name => self::DESC),
 			);
 		} else {
 			return false;
diff --git a/tests/unit/framework/db/QueryTest.php b/tests/unit/framework/db/QueryTest.php
index 645b844..2c4359f 100644
--- a/tests/unit/framework/db/QueryTest.php
+++ b/tests/unit/framework/db/QueryTest.php
@@ -14,13 +14,13 @@ class QueryTest extends \yiiunit\MysqlTestCase
 		// default
 		$query = new Query;
 		$query->select('*');
-		$this->assertEquals('*', $query->select);
+		$this->assertEquals(array('*'), $query->select);
 		$this->assertNull($query->distinct);
 		$this->assertEquals(null, $query->selectOption);
 
 		$query = new Query;
 		$query->select('id, name', 'something')->distinct(true);
-		$this->assertEquals('id, name', $query->select);
+		$this->assertEquals(array('id','name'), $query->select);
 		$this->assertTrue($query->distinct);
 		$this->assertEquals('something', $query->selectOption);
 	}
@@ -29,7 +29,7 @@ class QueryTest extends \yiiunit\MysqlTestCase
 	{
 		$query = new Query;
 		$query->from('tbl_user');
-		$this->assertEquals('tbl_user', $query->from);
+		$this->assertEquals(array('tbl_user'), $query->from);
 	}
 
 	function testWhere()
@@ -57,12 +57,12 @@ class QueryTest extends \yiiunit\MysqlTestCase
 	{
 		$query = new Query;
 		$query->groupBy('team');
-		$this->assertEquals('team', $query->groupBy);
+		$this->assertEquals(array('team'), $query->groupBy);
 
-		$query->addGroup('company');
+		$query->addGroupBy('company');
 		$this->assertEquals(array('team', 'company'), $query->groupBy);
 
-		$query->addGroup('age');
+		$query->addGroupBy('age');
 		$this->assertEquals(array('team', 'company', 'age'), $query->groupBy);
 	}
 
@@ -86,13 +86,19 @@ class QueryTest extends \yiiunit\MysqlTestCase
 	{
 		$query = new Query;
 		$query->orderBy('team');
-		$this->assertEquals('team', $query->orderBy);
+		$this->assertEquals(array('team' => false), $query->orderBy);
 
 		$query->addOrderBy('company');
-		$this->assertEquals(array('team', 'company'), $query->orderBy);
+		$this->assertEquals(array('team' => false, 'company' => false), $query->orderBy);
 
 		$query->addOrderBy('age');
-		$this->assertEquals(array('team', 'company', 'age'), $query->orderBy);
+		$this->assertEquals(array('team' => false, 'company' => false, 'age' => false), $query->orderBy);
+
+		$query->addOrderBy(array('age' => true));
+		$this->assertEquals(array('team' => false, 'company' => false, 'age' => true), $query->orderBy);
+
+		$query->addOrderBy('age ASC, company DESC');
+		$this->assertEquals(array('team' => false, 'company' => true, 'age' => false), $query->orderBy);
 	}
 
 	function testLimitOffset()