diff --git a/framework/yii/data/Sort.php b/framework/yii/data/Sort.php
index a466637..cb5dd82 100644
--- a/framework/yii/data/Sort.php
+++ b/framework/yii/data/Sort.php
@@ -358,4 +358,14 @@ class Sort extends Object
 		}
 		return implode($this->separators[0], $sorts);
 	}
+
+	/**
+	 * Returns a value indicating whether the sort definition supports sorting by the named attribute.
+	 * @param string $name the attribute name
+	 * @return boolean whether the sort definition supports sorting by the named attribute.
+	 */
+	public function hasAttribute($name)
+	{
+		return isset($this->attributes[$name]);
+	}
 }
diff --git a/framework/yii/db/ColumnSchema.php b/framework/yii/db/ColumnSchema.php
index 83453e4..cd2d9fa 100644
--- a/framework/yii/db/ColumnSchema.php
+++ b/framework/yii/db/ColumnSchema.php
@@ -7,13 +7,15 @@
 
 namespace yii\db;
 
+use yii\base\Object;
+
 /**
  * ColumnSchema class describes the metadata of a column in a database table.
  *
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-class ColumnSchema extends \yii\base\Component
+class ColumnSchema extends Object
 {
 	/**
 	 * @var string name of this column (without quotes).
diff --git a/framework/yii/db/Schema.php b/framework/yii/db/Schema.php
index 6ae9ab7..1aef764 100644
--- a/framework/yii/db/Schema.php
+++ b/framework/yii/db/Schema.php
@@ -8,6 +8,7 @@
 namespace yii\db;
 
 use Yii;
+use yii\base\Object;
 use yii\base\NotSupportedException;
 use yii\base\InvalidCallException;
 use yii\caching\Cache;
@@ -25,7 +26,7 @@ use yii\caching\GroupDependency;
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-abstract class Schema extends \yii\base\Object
+abstract class Schema extends Object
 {
 	/**
 	 * The followings are the supported abstract column data types.
diff --git a/framework/yii/db/TableSchema.php b/framework/yii/db/TableSchema.php
index 1065b51..cad4c0a 100644
--- a/framework/yii/db/TableSchema.php
+++ b/framework/yii/db/TableSchema.php
@@ -7,6 +7,7 @@
 
 namespace yii\db;
 
+use yii\base\Object;
 use yii\base\InvalidParamException;
 
 /**
@@ -17,7 +18,7 @@ use yii\base\InvalidParamException;
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-class TableSchema extends \yii\base\Object
+class TableSchema extends Object
 {
 	/**
 	 * @var string name of the catalog (database) that this table belongs to.