diff --git a/docs/api/db/ActiveRecord-find.md b/docs/api/db/ActiveRecord-find.md
index 39ab80f..570c423 100644
--- a/docs/api/db/ActiveRecord-find.md
+++ b/docs/api/db/ActiveRecord-find.md
@@ -1,5 +1,5 @@
-Because [[ActiveQuery]] implements a set of query building methods,
-additional query conditions can be specified by calling the methods of [[ActiveQuery]].
+The returned [[ActiveQuery]] instance can be further customized by calling
+methods defined in [[ActiveQuery]] before returning the populated active records.
 
 Below are some examples:
 
diff --git a/docs/api/db/ActiveRecord.md b/docs/api/db/ActiveRecord.md
index 8b13789..27eeb31 100644
--- a/docs/api/db/ActiveRecord.md
+++ b/docs/api/db/ActiveRecord.md
@@ -1 +1,353 @@
+ActiveRecord implements the [Active Record design pattern](http://en.wikipedia.org/wiki/Active_record).
+An ActiveRecord object is associated with a row in a database table. For example, a `Customer` object
+is associated with a row in the `tbl_customer` table. Instead of writing raw SQL statements to access
+the data in the table, one can call intuitive methods available in the corresponding ActiveRecord class
+to achieve the same goals. For example, calling [[save()]] would insert or update a row
+in the underlying table.
 
+
+### Declaring ActiveRecord Classes
+
+An ActiveRecord class is declared by extending [[\yii\db\ActiveRecord]]. It typically requires the following
+minimal code:
+
+~~~
+class Customer extends \yii\db\ActiveRecord
+{
+	/**
+	 * @return string the name of the table associated with this ActiveRecord class.
+	 */
+	public static function tableName()
+	{
+		return 'tbl_customer';
+	}
+}
+~~~
+
+
+### Connecting to Database
+
+ActiveRecord relies on a [[Connection|DB connection]] to perform DB-related operations. By default,
+it assumes that an application component named `db` gives the needed [[Connection]] instance
+which serves as the DB connection. The following application configuration shows an example:
+
+~~~
+return array(
+	'components' => array(
+		'db' => array(
+			'class' => 'yii\db\Connection',
+			'dsn' => 'mysql:host=localhost;dbname=testdb',
+			'username' => 'demo',
+			'password' => 'demo',
+			// turn on schema caching to improve performance
+			// 'schemaCacheDuration' => 3600,
+		),
+	),
+);
+~~~
+
+
+### Retrieving Data from Database
+
+ActiveRecord provides three methods for data retrieval purpose:
+
+- [[find()]]
+- [[findBySql()]]
+- [[count()]]
+
+They all return an [[ActiveQuery]] instance. Coupled with the various customization and query methods
+provided by [[ActiveQuery]], ActiveRecord supports very flexible and powerful data retrieval approaches.
+
+The followings are some examples,
+
+~~~
+// to retrieve all *active* customers and order them by their ID:
+$customers = Customer::find()
+	->where(array('status' => $active))
+	->orderBy('id')
+	->all();
+
+// to return a single customer whose ID is 1:
+$customer = Customer::find()
+	->where(array('id' => 1))
+	->one();
+
+// or use the following shortcut approach:
+$customer = Customer::find(1);
+
+// to retrieve customers using a raw SQL statement:
+$sql = 'SELECT * FROM tbl_customer';
+$customers = Customer::findBySql($sql)->all();
+
+// to return the number of *active* customers:
+$count = Customer::count()
+	->where(array('status' => $active))
+	->value();
+
+// to return customers in terms of arrays rather than `Customer` objects:
+$customers = Customer::find()->asArray()->all();
+// each $customers element is an array of name-value pairs
+
+// to index the result by customer IDs:
+$customers = Customer::find()->indexBy('id')->all();
+// $customers array is indexed by customer IDs
+~~~
+
+
+### Accessing Column Data
+
+ActiveRecord maps each column in the associated row of database table to an *attribute* in the ActiveRecord
+object. An attribute is like a regular object property whose name is the same as the corresponding column
+name and is case sensitive.
+
+To read the value of a column, we can use the following expression:
+
+~~~
+// "id" is the name of a column in the table associated with $customer ActiveRecord object
+$id = $customer->id;
+// or alternatively,
+$id = $customer->getAttribute('id');
+~~~
+
+And through the [[attributes]] property, we can get all column values:
+
+~~~
+$values = $customer->attributes;
+~~~
+
+
+### Persisting Data to Database
+
+ActiveRecord provides the following methods to support data insertion, updating and deletion:
+
+- [[save()]]
+- [[insert()]]
+- [[update()]]
+- [[delete()]]
+- [[updateCounters()]]
+- [[updateAll()]]
+- [[updateAllCounters()]]
+- [[deleteAll()]]
+
+Note that [[updateAll()]], [[updateAllCounters()]] and [[deleteAll()]] apply to the whole database
+table, while the rest of the methods only apply to the row associated with the ActiveRecord object.
+
+The followings are some examples:
+
+~~~
+// to insert a new customer record
+$customer = new Customer;
+$customer->name = 'James';
+$customer->email = 'james@example.com';
+$customer->save();  // equivalent to $customer->insert();
+
+// to update an existing customer record
+$customer = Customer::find($id);
+$customer->email = 'james@example.com';
+$customer->save();  // equivalent to $customer->update();
+
+// to delete an existing customer record
+$customer = Customer::find($id);
+$customer->delete();
+
+// to increment the age of all customers by 1
+Customer::updateAllCounters(array('age' => 1));
+~~~
+
+
+### Retrieving Relational Data
+
+ActiveRecord supports foreign key relationships by exposing them via component properties. For example,
+with appropriate declaration, the expression `$customer->orders` can return an array of `Order` objects
+which represent the orders placed by the specified customer.
+
+To declare a relationship, define a getter method which returns an [[ActiveRelation]] object. For example,
+
+~~~
+class Customer extends \yii\db\ActiveRecord
+{
+	public function getOrders()
+	{
+		return $this->hasMany('Order', array('customer_id' => 'id'));
+	}
+}
+
+class Order extends \yii\db\ActiveRecord
+{
+	public function getCustomer()
+	{
+		return $this->hasOne('Customer', array('id' => 'customer_id'));
+	}
+}
+~~~
+
+Within the getter methods, we call [[hasMany()]] or [[hasOne()]] to create a new [[ActiveRelation]] object.
+The [[hasMany()]] method declares a one-many relationship. For example, a customer has many orders.
+And the [[hasOne()]] method declares a many-one or one-one relationship. For example, an order has one customer.
+Both methods take two parameters:
+
+- `$class`: the class name of the related models. If the class name is not namespaced, it will take
+  the same namespace as the declaring class.
+- `$link`: the association between columns from two tables. This should be given as an array.
+  The keys of the array are the names of the columns from the table associated with `$class`,
+  while the values of the array the names of the columns from the declaring class.
+
+Retrieving relational data is now as easy as accessing a component property. Remember that a component
+property is defined by the existence of a getter method. The The following example
+shows how to get the orders of a customer, and how to get the customer of the first order.
+
+~~~
+$customer = Customer::find($id);
+$orders = $customer->orders;  // $orders is an array of Order objects
+$customer2 = $orders[0]->customer;  // $customer == $customer2
+~~~
+
+Because [[ActiveRelation]] extends from [[ActiveQuery]], it has the same query customization methods,
+which allows us to customize the query for retrieving the related objects. For example, we may declare a `bigOrder`
+relationship which returns orders whose subtotal exceeds certain amount:
+
+~~~
+class Customer extends \yii\db\ActiveRecord
+{
+	public function getBigOrders()
+	{
+		return $this->hasMany('Order', array('customer_id' => 'id'))
+			->where('subtotal > 100')
+			->orderBy('id');
+	}
+}
+~~~
+
+
+Sometimes, two tables are related together via an intermediary table called
+[pivot table](http://en.wikipedia.org/wiki/Pivot_table). To declare such relationships, we can customize
+the [[ActiveRelation]] object by calling its [[ActiveRelation::via()]] or [[ActiveRelation::viaTable()]]
+method.
+
+For example, if table `tbl_order` and table `tbl_item` are related via pivot table `tbl_order_item`,
+we can declare the `items` relation in the `Order` class like the following:
+
+~~~
+class Order extends \yii\db\ActiveRecord
+{
+	public function getItems()
+	{
+		return $this->hasMany('Item', array('id' => 'item_id'))
+			->viaTable('tbl_order_item', array('order_id' => 'id'));
+	}
+}
+~~~
+
+Method [[ActiveRelation::via()]] is similar to [[ActiveRelation::viaTable()]] except that
+the first parameter of [[ActiveRelation::via()]] takes a relation name declared in the ActiveRecord class.
+For example, the above `items` relation can be equivalently declared as follows:
+
+~~~
+class Order extends \yii\db\ActiveRecord
+{
+	public function getOrderItems()
+	{
+		return $this->hasMany('OrderItem', array('order_id' => 'id'));
+	}
+
+	public function getItems()
+	{
+		return $this->hasMany('Item', array('id' => 'item_id'))
+			->via('orderItems');
+	}
+}
+~~~
+
+
+When we access the related objects the first time, behind the scene ActiveRecord will perform a DB query
+to retrieve the corresponding data and populate them into the related objects. No query will be perform
+if we access again the same related objects. We call this *lazy loading*. For example,
+
+~~~
+// SQL executed: SELECT * FROM tbl_customer WHERE id=1
+$customer = Customer::find(1);
+// SQL executed: SELECT * FROM tbl_order WHERE customer_id=1
+$orders = $customer->orders;
+// no SQL executed
+$orders2 = $customer->orders;
+~~~
+
+
+Lazy loading is convenient to use. However, it may suffer from performance issue in the following scenario:
+
+~~~
+// SQL executed: SELECT * FROM tbl_customer LIMIT 100
+$customers = Customer::find()->limit(100)->all();
+
+foreach ($customers as $customer) {
+	// SQL executed: SELECT * FROM tbl_order WHERE customer_id=...
+	$orders = $customer->orders;
+	// ...handle $orders...
+}
+~~~
+
+How many SQL queries will be performed in the above code, assuming there are more than 100 customers in
+the database? 101! The first SQL query brings back 100 customers. Then for each customer, a SQL query
+is performed to bring back the customer's orders.
+
+To solve the above performance problem, we can use the so-called *eager loading* by calling [[ActiveQuery::with()]]:
+
+~~~
+// SQL executed: SELECT * FROM tbl_customer LIMIT 100
+//               SELECT * FROM tbl_orders WHERE customer_id IN (1,2,...)
+$customers = Customer::find()->limit(100)
+	->with('orders')->all();
+
+foreach ($customers as $customer) {
+	// no SQL executed
+	$orders = $customer->orders;
+	// ...handle $orders...
+}
+~~~
+
+As we can see, only two SQL queries are needed for the same task.
+
+
+Sometimes, we may want to customize the relational queries on the fly. This can be done for both
+lazy loading and eager loading. For example,
+
+~~~
+$customer = Customer::find(1);
+// lazy loading: SELECT * FROM tbl_order WHERE customer_id=1 AND subtotal>100
+$orders = $customer->getOrders()->where('subtotal>100')->all();
+
+// eager loading: SELECT * FROM tbl_customer LIMIT 10
+                  SELECT * FROM tbl_order WHERE customer_id IN (1,2,...) AND subtotal>100
+$customers = Customer::find()->limit(100)->with(array(
+	'orders' => function($query) {
+		$query->andWhere('subtotal>100');
+	},
+))->all();
+~~~
+
+
+### Maintaining Relationships
+
+ActiveRecord provides the following two methods for establishing and breaking relationship
+between two ActiveRecord objects:
+
+- [[link()]]
+- [[unlink()]]
+
+For example, given a customer and a new order, we can use the following code to make the
+order owned by the customer:
+
+~~~
+$customer = Customer::find(1);
+$order = new Order;
+$order->subtotal = 100;
+$customer->link('orders', $order);
+~~~
+
+The [[link()]] call above will set the `customer_id` of the order to be the primary key
+value of `$customer` and then call [[save()]] to save the order into database.
+
+
+### Data Input and Validation
+
+// todo
\ No newline at end of file
diff --git a/framework/db/ActiveQuery.php b/framework/db/ActiveQuery.php
index d47ec18..90e508f 100644
--- a/framework/db/ActiveQuery.php
+++ b/framework/db/ActiveQuery.php
@@ -37,7 +37,6 @@ use yii\db\Exception;
  * - [[with]]: list of relations that this query should be performed with.
  * - [[indexBy]]: the name of the column by which the query result should be indexed.
  * - [[asArray]]: whether to return each record as an array.
- * - [[scopes]]: list of scopes that should be applied to this query.
  *
  * These options can be configured using methods of the same name. For example:
  *
@@ -69,32 +68,11 @@ class ActiveQuery extends Query
 	 */
 	public $asArray;
 	/**
-	 * @var array list of scopes that should be applied to this query
-	 */
-	public $scopes;
-	/**
 	 * @var string the SQL statement to be executed for retrieving AR records.
 	 * This is set by [[ActiveRecord::findBySql()]].
 	 */
 	public $sql;
 
-	/**
-	 * PHP magic method.
-	 * This method is overridden so that scope methods declared in [[modelClass]]
-	 * can be invoked as methods of ActiveQuery.
-	 * @param string $name
-	 * @param array $params
-	 * @return mixed|ActiveQuery
-	 */
-	public function __call($name, $params)
-	{
-		if (method_exists($this->modelClass, $name)) {
-			$this->scopes[$name] = $params;
-			return $this;
-		} else {
-			return parent::__call($name, $params);
-		}
-	}
 
 	/**
 	 * Executes query and returns all results as an array.
@@ -179,9 +157,6 @@ class ActiveQuery extends Query
 				$tableName = $modelClass::tableName();
 				$this->from = array($tableName);
 			}
-			if (!empty($this->scopes)) {
-				$this->applyScopes($this->scopes);
-			}
 			/** @var $qb QueryBuilder */
 			$qb = $db->getQueryBuilder();
 			$this->sql = $qb->build($this);
@@ -243,37 +218,6 @@ class ActiveQuery extends Query
 		return $this;
 	}
 
-	/**
-	 * Specifies the scopes to be applied to this query.
-	 *
-	 * The parameters to this method can be either one or multiple strings, or a single array
-	 * of scopes names and their corresponding customization parameters.
-	 *
-	 * The followings are some usage examples:
-	 *
-	 * ~~~
-	 * // find all active customers
-	 * Customer::find()->scopes('active')->all();
-	 * // find active customers whose age is greater than 30
-	 * Customer::find()->scopes(array(
-	 *     'active',
-	 *     'olderThan' => array(30),
-	 * ))->all();
-	 * // alternatively the above statement can be written as:
-	 * Customer::find()->active()->olderThan(30)->all();
-	 * ~~~
-	 * @return ActiveQuery the query object itself
-	 */
-	public function scopes()
-	{
-		$this->scopes = func_get_args();
-		if (isset($this->scopes[0]) && is_array($this->scopes[0])) {
-			// the parameter is given as an array
-			$this->scopes = $this->scopes[0];
-		}
-		return $this;
-	}
-
 	private function createModels($rows)
 	{
 		$models = array();
@@ -352,17 +296,4 @@ class ActiveQuery extends Query
 		}
 		return $relations;
 	}
-
-	private function applyScopes($scopes)
-	{
-		$modelClass = $this->modelClass;
-		foreach ($scopes as $name => $config) {
-			if (is_integer($name)) {
-				$modelClass::$config($this);
-			} else {
-				array_unshift($config, $this);
-				call_user_func_array(array($modelClass, $name), $config);
-			}
-		}
-	}
 }
diff --git a/framework/db/ActiveRecord.php b/framework/db/ActiveRecord.php
index 90d817d..860a388 100644
--- a/framework/db/ActiveRecord.php
+++ b/framework/db/ActiveRecord.php
@@ -20,7 +20,7 @@ use yii\db\Expression;
 use yii\util\StringHelper;
 
 /**
- * ActiveRecord is the base class for classes representing relational data.
+ * ActiveRecord is the base class for classes representing relational data in terms of objects.
  *
  * @include @yii/db/ActiveRecord.md
  *
@@ -1127,9 +1127,10 @@ abstract class ActiveRecord extends Model
 	 * @param ActiveRecord $model the model to be unlinked from the current one.
 	 * @param boolean $delete whether to delete the model that contains the foreign key.
 	 * If false, the model's foreign key will be set null and saved.
+	 * If true, the model containing the foreign key will be deleted.
 	 * @throws BadParamException if the models cannot be unlinked
 	 */
-	public function unlink($name, $model, $delete = true)
+	public function unlink($name, $model, $delete = false)
 	{
 		$relation = $this->getRelation($name);
 
diff --git a/tests/unit/data/ar/Customer.php b/tests/unit/data/ar/Customer.php
index d242f4d..a04694a 100644
--- a/tests/unit/data/ar/Customer.php
+++ b/tests/unit/data/ar/Customer.php
@@ -19,13 +19,4 @@ class Customer extends ActiveRecord
 	{
 		return $this->hasMany('Order', array('customer_id' => 'id'))->orderBy('id');
 	}
-
-	/**
-	 * @param ActiveQuery $query
-	 * @return ActiveQuery
-	 */
-	public static function active($query)
-	{
-		return $query->andWhere(array('status' => self::STATUS_ACTIVE));
-	}
 }
\ No newline at end of file
diff --git a/tests/unit/framework/db/ActiveRecordTest.php b/tests/unit/framework/db/ActiveRecordTest.php
index 6cf0ea2..a0809b1 100644
--- a/tests/unit/framework/db/ActiveRecordTest.php
+++ b/tests/unit/framework/db/ActiveRecordTest.php
@@ -95,15 +95,6 @@ class ActiveRecordTest extends \yiiunit\MysqlTestCase
 		$this->assertEquals('user2', $customer->name);
 	}
 
-	public function testScope()
-	{
-		$customers = Customer::find()->scopes('active')->all();
-		$this->assertEquals(2, count($customers));
-
-		$customers = Customer::find()->active()->all();
-		$this->assertEquals(2, count($customers));
-	}
-
 	public function testFindLazy()
 	{
 		/** @var $customer Customer */
@@ -256,7 +247,7 @@ class ActiveRecordTest extends \yiiunit\MysqlTestCase
 		// has many
 		$customer = Customer::find(2);
 		$this->assertEquals(2, count($customer->orders));
-		$customer->unlink('orders', $customer->orders[1]);
+		$customer->unlink('orders', $customer->orders[1], true);
 		$this->assertEquals(1, count($customer->orders));
 		$this->assertNull(Order::find(3));
 
@@ -264,14 +255,14 @@ class ActiveRecordTest extends \yiiunit\MysqlTestCase
 		$order = Order::find(2);
 		$this->assertEquals(3, count($order->items));
 		$this->assertEquals(3, count($order->orderItems));
-		$order->unlink('items', $order->items[2]);
+		$order->unlink('items', $order->items[2], true);
 		$this->assertEquals(2, count($order->items));
 		$this->assertEquals(2, count($order->orderItems));
 
 		// via table
 		$order = Order::find(1);
 		$this->assertEquals(2, count($order->books));
-		$order->unlink('books', $order->books[1]);
+		$order->unlink('books', $order->books[1], true);
 		$this->assertEquals(1, count($order->books));
 		$this->assertEquals(1, count($order->orderItems));
 	}