CREATE OBJ_SUPER1 as object
(num1 number,
 num2 number,
 str1 varchar2(100),
 date1 date,
 MEMBER FUNCTION getNum1 RETURN NUMBER,
 MEMBER FUNCTION getStr1 RETURN VARCHAR2,
 MEMBER FUNCTION getDate RETURN DATE
) NOT FINAL;

CREATE TYPE BODY OBJ_SUPER1 AS
-- list supertype methods' body

CREATE OBJ_MY_SUB1 UNDER OBJ_SUPER1
(  subnum1 number,
   subnum2 number,
   subdate1 date,
   MEMBER FUNCTION subnum1 RETURN NUMBER,
   MEMBER FUNCTION subdate1 RETURN NUMBER
) NOT FINAL
/

CREATE TYPE BODY OBJ_MY_SUB1 AS
-- list subtype methods' body

SQL> CREATE TYPE parentType AS OBJECT
  2  (
  3      parentAttr1 NUMBER
  4  ) NOT FINAL;
  5  /

Type created.

SQL> SHOW ERRORS;
No errors.
SQL> 
SQL> CREATE TYPE childType UNDER parentType
  2  (
  3      childAttr DATE
  4  );
  5  /

Type created.

SQL> SHOW ERRORS;
No errors.
SQL> 
SQL> ALTER TYPE parentType ADD ATTRIBUTE parentAttr2 NUMBER CASCADE;

Type altered.

SQL> SHOW ERRORS;
No errors.
SQL> 
SQL> 
SQL> DESCRIBE childType;
 childType extends TRAINING.PARENTTYPE
 Name					   Null?    Type
 ----------------------------------------- -------- ----------------------------
 PARENTATTR1					    NUMBER
 PARENTATTR2					    NUMBER
 CHILDATTR					    DATE

SQL>