function _define_class_properties()
	{
		return complex_array :: array_merge(
					parent :: _define_attributes_definition(),
					array('abstract_class' => true)
				);
	}
	function _define_attributes_definition()
	{
		return complex_array :: array_merge(
				parent :: _define_attributes_definition(),
				array(
				'question' => array('search' => true),
				'answer' => array('search' => true)
				));
	}
 function _define_attributes_definition()
 {
   return complex_array :: array_merge(
       parent :: _define_attributes_definition(),
       array(
       'content' => array('search' => true),
       'annotation' => array('search' => true),
       'identifier' => array('search' => false)
       ));
 }
 function _define_attributes_definition()
 {
   return complex_array :: array_merge(
       parent :: _define_attributes_definition(),
       array(
       'second_password' => '',
       ));
 }
	function _define_attributes_definition()
	{
		return complex_array :: array_merge(
				parent :: _define_attributes_definition(),
				array(
				'identifier' => array('search' => true)
				));
	}
 function _define_attributes_definition()
 {
   return complex_array :: array_merge(
       parent :: _define_attributes_definition(),
       array(
       'content' => array('search' => true, 'search_weight' => 1),
       ));
 }
	function _define_attributes_definition()
	{
		return complex_array :: array_merge(
				parent :: _define_attributes_definition(),
				array(
					'content' => array('search' => true, 'search_weight' => 1),
					'annotation' => array('search' => true, 'search_weight' => 5),
					'author' => array('search' => true, 'search_weight' => 10),
					'source' => array('search' => true, 'search_weight' => 10),
				));
	}