Why can't I have an object with no attributes?

Why can't I have an object with no attributes? How else can I make an interface definition? How can I extend an object with additional methods but no additional attributes?

For example ...

create or replace type tobj is object (

    member function foobar

        return varchar2
    );
/

show errors

PLS-00589: no attributes found in object type "TOBJ"

Thanks,
Richard Received on Wed Jun 11 2003 - 14:02:44 CDT