public function rules()
{
return array(array('action, model, field, stamp, model_id', 'required'), array('action, model, field', 'length', 'max' => 255), array('model_id, user_id', 'numerical', 'integerOnly' => true), array('id, new_value, old_value, action, model, field, stamp, user_id, model_id', 'safe', 'on' => 'search'));
}