DDS-XTypes 1.3 RTF Avatar
  1. OMG Issue

DDSXTY13 — Inheritance rules not sufficient regarding keys and memberID assignment

  • Key: DDSXTY13-23
  • Status: open  
  • Source: Real-Time Innovations ( Gerardo Pardo-Castellote)
  • Summary:

    XTYPES should specify that if a type declares key members then derived types cannot add additional key members.

    The reason is that the derived type will never be compatible with the base type according to the compatibility rules so there is no purpose on allowing that inheritance which would mislead the user.

    Semantically it seems that extending the key breaks the substitution principle where a derived class can be used in place of a base-class anywhere. If we allowed key extension two different objects could appear to be the same when viewed as a "base class"

    Additionally in section 'Member IDs' there is no mention of how inheritance impacts the automatic assignment of member IDs.

  • Reported: DDS-XTypes 1.2 — Fri, 20 Apr 2018 13:02 GMT
  • Updated: Mon, 1 Apr 2019 17:40 GMT