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  1. OMG Issue

CORBA35 — Implications of any/valuetype marshalling

  • Key: CORBA35-172
  • Legacy Issue Number: 4137
  • Status: open  
  • Source: Iconixx ( Thomas Hawker)
  • Summary:

    RE: CCM chapters document [orbrev] 99-10-04, section 61.6.2, page 61-45.
    The document citation indicates that the integrity of the valuetype –
    that is, the received marshalled state – is to be preserved in an
    ORB-mediated operation, even if that valuetype cannot be unmarshalled,
    either partially (truncated) or at all. If this value is then passed to
    another operation, the original marshalled state is to be transmitted.
    This preserves the transmitted object in its entirety, regardless of
    local implementation concerns. This is obviously necessary for bridges
    or event processing, such as through the notification service.

    So the question arises, what happens if you have a partial (truncated)
    unmarshall and the recipient application changes the local state of the
    valuetype through its attributes or local operations? How can/will you
    even know the state was changed? Do you ignore the changes and send the
    originally received marshalled stream, send only the new valuetype even
    though it is a truncation of the original, or "merge" the new values for
    the unmarshalled part followed by the original appended data for the
    truncated part? Should this third option be possible through an
    explicit ORB call – that is, the application is responsible to identify
    the change in state to the ORB? I assume that the semantics of
    "truncatable" must come to include the understanding that data in the
    truncatable portions may not be contextually dependent on the inherited
    parent of the valuetype.

    As a further question, is there a reason why this semantic
    interpretation should not be extended to be a general requirement rather
    than only with respect to transmission of anys? My experience has found
    that passing anys tends to be expensive and is avoided where it can be.
    A more general interpretation permits transmission of a comprehensive
    data structure among intermediate agents that only use (unmarshall) the
    information they need.

  • Reported: CORBA 2.4.1 — Fri, 5 Jan 2001 05:00 GMT
  • Updated: Wed, 6 Dec 2023 23:15 GMT