DDSXTY — Provide minimal backwards-compatible conformance point

One of the reasons for the development of the DDS-XTypes specification was the prior lack of explicitness and formality in the DDS type system and in its representations. DDS-XTypes addresses this need—and simultaneously extends both the type system and its representations. It would help the discourse about DDS systems, and the modeling of DDS systems, if a subset of DDS-XTypes were defined that identified only those parts of DDS and/or DDS-RTPS that were in broad use before the existence of DDS-XTypes.
This subset would include the following:
• A subset of the Type System:
o The full set of primitive types
o Strings of narrow or wide characters
o Sequences
o Aliases
o Structures without inheritance and with “final” extensibility
o Enumerations
o Unions
• The IDL Type Representation of the above
• The CDR Data Representation of the above
• The Plain Language Binding for the above

Identify the above subset of the specification in a new, non-normative, annex