The query results in:

<?xml version=”1.0″?> <EMP/>

With:
CREATE OR REPLACE TYPE BODY hrm_employee_obj
IS
CONSTRUCTOR FUNCTION hrm_employee_obj
RETURN SELF AS RESULT
IS
BEGIN
department := hrm_department_obj();
RETURN;
END;
END;

The query results in:

<?xml version=”1.0″?> <EMP> <DEPARTMENT/> </EMP>

SQL>set serveroutput on
SQL>create or replace type obj1 as object
  2  ( name varchar2(100) );
  3  /
Type created.
SQL>create or replace type obj2 as object
  2  ( name varchar2(100)
  3  , o1 obj1
  4  , constructor function obj2 return self as result 
  5  );
  6  /
Type created.
SQL>create or replace type body obj2
  2  as
  3    constructor function obj2 return self as result
  4    is
  5    begin
  6      return;
  7    end;
  8  end; 
  9  /
Type body created.
SQL>declare
  2   o2 obj2;
  3   o3 obj2;
  4  begin
  5    o2 := obj2();
  6    o2.name := ‘Hello’;
  7    o2.o1 := obj1( ‘World’ );
  8    dbms_output.put_line( o2.name || ‘ ‘ || o2.o1.name );
  9    o3 := obj2( ‘Hallo’, obj1( ‘Wereld’ ) );
 10    dbms_output.put_line( o3.name || ‘ ‘ || o3.o1.name );
 11  end;
 12  /
Hello World
Hallo Wereld
PL/SQL procedure successfully completed.
SQL>