diff --git a/docs/api/db/ActiveRecord.md b/docs/api/db/ActiveRecord.md
index b6e6041..cf4e0b1 100644
--- a/docs/api/db/ActiveRecord.md
+++ b/docs/api/db/ActiveRecord.md
@@ -363,4 +363,86 @@ value of `$customer` and then call [[save()]] to save the order into database.
 
 ### Data Input and Validation
 
-// todo
\ No newline at end of file
+TBD
+
+
+### Life Cycles of an ActiveRecord Object
+
+An ActiveRecord object undergoes different life cycles when it is used in different cases.
+Subclasses or ActiveRecord behaviors may "inject" custom code in these life cycles through
+method overriding and event handling mechanisms.
+
+When instantiating a new ActiveRecord instance, we will have the following life cycles:
+
+1. constructor
+2. [[init()]]: will trigger an [[init]] event
+
+When getting an ActiveRecord instance through the [[find()]] method, we will have the following life cycles:
+
+1. constructor
+2. [[init()]]: will trigger an [[init]] event
+3. [[afterFind()]]: will trigger an [[afterFind]] event
+
+When calling [[save()]] to insert or update an ActiveRecord, we will have the following life cycles:
+
+1. [[beforeValidate()]]: will trigger an [[beforeValidate]] event
+2. [[beforeSave()]]: will trigger an [[beforeSave]] event
+3. perform the actual data insertion or updating
+4. [[afterSave()]]: will trigger an [[afterSave]] event
+5. [[afterValidate()]]: will trigger an [[afterValidate]] event
+
+Finally when calling [[delete()]] to delete an ActiveRecord, we will have the following life cycles:
+
+1. [[beforeDelete()]]: will trigger an [[beforeDelete]] event
+2. perform the actual data deletion
+3. [[afterDelete()]]: will trigger an [[afterDelete]] event
+
+
+### Scopes
+
+A scope is a method that customizes a given [[ActiveQuery]] object. Scope methods are defined
+in the ActiveRecord classes. They can be invoked through the [[ActiveQuery]] object that is created
+via [[find()]] or [[findBySql()]]. The following is an example:
+
+~~~
+class Customer extends \yii\db\ActiveRecord
+{
+	// ...
+
+	/**
+	 * @param ActiveQuery $query
+	 */
+	public function active($query)
+	{
+		$query->andWhere('status = 1');
+	}
+}
+
+$customers = Customer::find()->active()->all();
+~~~
+
+In the above, the `active()` method is defined in `Customer` while we are calling it
+through `ActiveQuery` returned by `Customer::find()`.
+
+Scopes can be parameterized. For example, we can define and use the following `olderThan` scope:
+
+~~~
+class Customer extends \yii\db\ActiveRecord
+{
+	// ...
+
+	/**
+	 * @param ActiveQuery $query
+	 * @param integer $age
+	 */
+	public function olderThan($query, $age = 30)
+	{
+		$query->andWhere('age > :age', array(':age' => $age));
+	}
+}
+
+$customers = Customer::find()->olderThan(50)->all();
+~~~
+
+The parameters should follow after the `$query` parameter when defining the scope method, and they
+can take default values like shown above.
diff --git a/framework/base/Object.php b/framework/base/Object.php
index ddfe36b..a3425dc 100644
--- a/framework/base/Object.php
+++ b/framework/base/Object.php
@@ -78,7 +78,8 @@ class Object
 	 * will be implicitly called when executing `$object->property = $value;`.
 	 * @param string $name the property name or the event name
 	 * @param mixed $value the property value
-	 * @throws UnknownPropertyException if the property is not defined or read-only.
+	 * @throws UnknownPropertyException if the property is not defined
+	 * @throws InvalidCallException if the property is read-only.
 	 * @see __get
 	 */
 	public function __set($name, $value)
@@ -122,7 +123,7 @@ class Object
 	 * Note that if the property is not defined, this method will do nothing.
 	 * If the property is read-only, it will throw an exception.
 	 * @param string $name the property name
-	 * @throws UnknownPropertyException if the property is read only.
+	 * @throws InvalidCallException if the property is read only.
 	 */
 	public function __unset($name)
 	{
diff --git a/framework/db/ActiveQuery.php b/framework/db/ActiveQuery.php
index dc857ef..df81a07 100644
--- a/framework/db/ActiveQuery.php
+++ b/framework/db/ActiveQuery.php
@@ -14,7 +14,6 @@ use yii\db\Connection;
 use yii\db\Command;
 use yii\db\QueryBuilder;
 use yii\db\Expression;
-use yii\db\Exception;
 
 /**
  * ActiveQuery represents a DB query associated with an Active Record class.
diff --git a/framework/db/ActiveRecord.php b/framework/db/ActiveRecord.php
index 4647067..a1b9313 100644
--- a/framework/db/ActiveRecord.php
+++ b/framework/db/ActiveRecord.php
@@ -32,6 +32,8 @@ use yii\util\StringHelper;
  * @property mixed $primaryKey the primary key value.
  * @property mixed $oldPrimaryKey the old primary key value.
  *
+ * @event ModelEvent init an event that is triggered when the record is initialized (in [[init()]]).
+ * @event ModelEvent afterFind an event that is triggered after the record is created and populated with query result.
  * @event ModelEvent beforeInsert an event that is triggered before inserting a record.
  * You may set [[ModelEvent::isValid]] to be false to stop the insertion.
  * @event Event afterInsert an event that is triggered before inserting a record.
@@ -762,6 +764,30 @@ class ActiveRecord extends Model
 	}
 
 	/**
+	 * Initializes the object.
+	 * This method is called at the end of the constructor.
+	 * The default implementation will trigger an [[afterInsert]] event.
+	 * If you override this method, make sure you call the parent implementation at the end
+	 * to ensure triggering of the event.
+	 */
+	public function init()
+	{
+		parent::init();
+		$this->trigger('init');
+	}
+
+	/**
+	 * This method is called when the AR object is created and populated with the query result.
+	 * The default implementation will trigger an [[afterFind]] event.
+	 * When overriding this method, make sure you call the parent implementation to ensure the
+	 * event is triggered.
+	 */
+	public function afterFind()
+	{
+		$this->trigger('afterFind');
+	}
+
+	/**
 	 * Sets the value indicating whether the record is new.
 	 * @param boolean $value whether the record is new and should be inserted when calling [[save()]].
 	 * @see getIsNewRecord
@@ -956,6 +982,7 @@ class ActiveRecord extends Model
 			}
 		}
 		$record->_oldAttributes = $record->_attributes;
+		$record->afterFind();
 		return $record;
 	}
 
diff --git a/framework/db/Schema.php b/framework/db/Schema.php
index bb4352a..ff7cc72 100644
--- a/framework/db/Schema.php
+++ b/framework/db/Schema.php
@@ -329,10 +329,10 @@ abstract class Schema extends \yii\base\Object
 
 	/**
 	 * Extracts the PHP type from abstract DB type.
-	 * @param string $type abstract DB type
+	 * @param ColumnSchema $column the column schema information
 	 * @return string PHP type name
 	 */
-	protected function getColumnPhpType($type)
+	protected function getColumnPhpType($column)
 	{
 		static $typeMap = array( // abstract type => php type
 			'smallint' => 'integer',
@@ -341,13 +341,13 @@ abstract class Schema extends \yii\base\Object
 			'boolean' => 'boolean',
 			'float' => 'double',
 		);
-		if (isset($typeMap[$type])) {
-			if ($type === 'bigint') {
-				return PHP_INT_SIZE == 8 && !$this->unsigned ? 'integer' : 'string';
-			} elseif ($type === 'integer') {
-				return PHP_INT_SIZE == 4 && $this->unsigned ? 'string' : 'integer';
+		if (isset($typeMap[$column->type])) {
+			if ($column->type === 'bigint') {
+				return PHP_INT_SIZE == 8 && !$column->unsigned ? 'integer' : 'string';
+			} elseif ($column->type === 'integer') {
+				return PHP_INT_SIZE == 4 && $column->unsigned ? 'string' : 'integer';
 			} else {
-				return $typeMap[$this->type];
+				return $typeMap[$column->type];
 			}
 		} else {
 			return 'string';
diff --git a/framework/db/mysql/Schema.php b/framework/db/mysql/Schema.php
index 82e02f0..f7826ed 100644
--- a/framework/db/mysql/Schema.php
+++ b/framework/db/mysql/Schema.php
@@ -165,7 +165,7 @@ class Schema extends \yii\db\Schema
 			}
 		}
 
-		$column->phpType = $this->getColumnPhpType($column->type);
+		$column->phpType = $this->getColumnPhpType($column);
 
 		if ($column->type !== 'timestamp' || $info['Default'] !== 'CURRENT_TIMESTAMP') {
 			$column->defaultValue = $column->typecast($info['Default']);