DDS-XTypes 1.3 RTF Avatar
  1. OMG Issue

DDSXTY13 — Union discriminator value without associated member

  • Key: DDSXTY13-10
  • Status: closed  
  • Source: Airbus Group ( Mr. Oliver M. Kellogg)
  • Summary:

    The DDS-XTypes 1.2-beta1 document section (Union Types) on page 34 first paragraph states:

    > [...]
    > (Note that it is not required for every potential discriminator value to be
    > associated with a member.)

    Supporting this, (Notation used for the match criteria) on p.121 states:

    > O : UNION_TYPE An object "O" of a Union type as defined in
    > [...]
    > * O.selected_member is the member of the union selected
    > based on the value of the discriminator. Note that certain
    > discriminator values may select no member.

    However, (Omission and Reordering of Members of Aggregated Types) on page 110 third para states:

    > Because union members are identified based on a discriminator value,
    > the value of the discriminator member must be serialized before the
    > value of the current non-discriminator member.
    > Neither member value may be omitted.

    I suggest replacing "Neither member value may be omitted" by:

    " The discriminator value may not be omitted.
    If the discriminator value has an associated member then the member value may not be omitted. "

    Section (Operation: get_item_count) on page 185 states:

    > The "item count" of the data depends on the type of the object.
    > * If the object is of a union type, return the number of members in the
    > object. This value will always be two: the discriminator and the current
    > member corresponding to it.

    I suggest replacing the last sentence by:

    " This value will be two if the discriminator value has a corresponding member. It will be one if the discriminator value has no corresponding member. "

  • Reported: DDS-XTypes 1.2b1 — Wed, 29 Nov 2017 16:12 GMT
  • Disposition: Resolved — DDS-XTypes 1.3
  • Disposition Summary:

    Modify the description of union serializarion

    Indicate that in the case of a union the only mandatory thing to serialize is the discriminator. The member may be omitted if no branch is selected.

  • Updated: Tue, 8 Oct 2019 17:55 GMT