'lv_zcl_xml' is not convertable to type 'ls_obj_ref-prt'

Hi all,

DATA: ls_obj_ref TYPE ty_obj_ref ,

lv_zcl_xml TYPE REF TO zcl_xml_local.

ls_obj_ref-prt = lv_zcl_xml.

where zcl_xml_local is class.

I am new to oops concept ... can anyone tell me what is wrong in this case ?

it is showing error saying that 'lv_zcl_xml' is not convertable to type 'ls_obj_ref-prt'.

thanks in advance.....