CORBA 2.5 NO IDEA Avatar
  1. OMG Issue

CORBA25 — Local interface is-a Object?

  • Key: CORBA25-39
  • Legacy Issue Number: 4388
  • Status: closed  
  • Source: Triodia Technologies Pty Ltd ( Michi Henning)
  • Summary:

    For local interfaces, we seem to have internal inconsistencies in the spec.
    For one, it is not clear whether or not a local interface implicitly inherits
    from Object. There is one sentence in the spec that seems to imply that
    there is implicit inheritance from object, on page 3-23 of the 2.5 draft

    Any attempt to marshal a local object, such as via an unconstrained
    base interface, as an Object, or as the contents of an any, or to
    pass a local object to ORB::object_to_string, shall result in a
    MARSHAL system exception with OMG minor code 4.

    This implies that I can at least try to pass local object as CORBA::Object,
    which implies that local interfaces do indeed implicitly inherit from Object.

    But then, a bit further down, it says:

    The is_a, get_interface, get_domain_managers, get_policy,
    get_client_policy, set_policy_overrides, get_policy_overrides, and
    validate_connection pseudo-operations, and any DII support
    pseudo-operations, may result in a NO_IMPLEMENT system exception
    with minor code 3 when invoked on a reference to a local object.

    "May result in a NO_IMPLEMENT system exception"? I would suggest "shall"!

    But, more seriously, I can't call is_a() on a local interface. In turn,
    that seems to imply that I can't narrow a local interface either, but
    narrowing is clearly necessary in the presence of inheritance for local

    It seems that local interfaces must inherit from Object. After all,
    it would be difficult to see, for example, how resolve_initial_references
    can return a reference to the Root POA if it were otherwise... But then,
    if local interfaces do inherit from Object, It doesn't make sense to
    prohibit calling is_a() on them.

    Related to that then is the question of "What is the repository ID of
    a local interface?" Given that they can be narrowed, it would seem that
    they must have repository IDs. (Although, you could argue that narrowing
    is to be achieved via some mechanism other than repository IDs – that
    would also permit is_a() not to be supported and would make narrowing
    an issue that is specific to each language mapping.)

    But the inheritance issue seems serious – if something doesn't inherit
    from Object, I can't return or pass it as an Object, but we are doing
    just that for local objects.

    I think this will require some careful thought. We don't want to find
    ourselves in yet another maze of twisty little passages, all different,
    as we did with pseudo-objects...

  • Reported: CORBA 2.4.2 — Fri, 29 Jun 2001 04:00 GMT
  • Disposition: Resolved — CORBA 2.5
  • Disposition Summary:

    Incorporate changes and close issue

  • Updated: Fri, 6 Mar 2015 20:58 GMT