protected $_defaultEntity = "Library_Database_Entity_Tree_Mptt";

    // Field list

    public $id = array("type" => "int", "primary" => true, "serial" => true);
    public $mptt_parent = array("type" => "int");
    public $mptt_left = array("type" => "int");
    public $mptt_right = array("type" => "int");

    // Parent relationship
    public $parent = array(
        'type' => 'relation',
        'relation' => 'HasOne',
        'mapper' => "Application_Mappers_TestMptt",
        'where' => array('mptt_parent' => 'entity.id')
        // Means the current mappers mptt_parent column = currently loaded Post entity id
    );