$user = ORM::factory('user')->where('name','=',$username)->find_all();

defined('SYSPATH') or die('No direct script access.');

class Model_User extends ORM {

	public function get_users($filters = array())
	{
                $user = ORM::factory('user')->where(...
         }
}

$filters = array('username'=>'Alex');
$users = ORM::factory('user')->get_users($filters);

$user = ORM::factory('user')
		->where_open()
		->where('username','LIKE',$name)
		->or_where('surname','=',$surname)
		->where_close()
		->find_all();