DTD Handling @dtd_element: @user_data: @dtd: @callback: @user_data: @dtd_element: @attr: @user_data: @dtd_element: @callback: @user_data: @content: @Returns: @dtd: @xml_node: @Returns: @content: @dtd_element: @Returns: @dtd: @content: @Returns: @dtd: @dtd_element: @callback: @user_data: @dtd: @dtd_element: @Returns: @dtd: @Returns: