Appendix G: Frame Identifiers (Informative Reference)

SpatialDDS represents reference frames using the FrameRef structure:

The normative IDL for FrameRef resides in Appendix A (Core profile). This appendix is descriptive/informative and restates the usage guidance for reference frames.

struct FrameRef {
  string uuid;   // globally unique frame ID
  string fqn;    // normalized fully-qualified name, e.g. "earth-fixed/map/cam_front"
};

UUID Rules

  • uuid is authoritative for identity.
  • fqn is an optional human-readable alias.
  • Implementations MUST treat uuid uniqueness as the identity key.
  • Deployments SHOULD establish well-known UUIDs for standard roots (e.g., earth-fixed, map, body) and document them for participants.

Name and Hierarchy Rules

  • fqn components are slash-delimited.
  • Reserved roots include earth-fixed, map, body, anchor, local.
  • A FrameRef DAG MUST be acyclic.

Manifest References

Manifest entries that refer to frames MUST use a FrameRef object rather than raw strings. Each manifest MAY define local frame aliases resolvable by fqn.

Notes

Derived schemas (e.g. GeoPose, Anchors) SHALL refer to the Appendix A definition by reference and MUST NOT re-declare frame semantics. The conventions in §2.1 and the coverage/discovery rules in §3.3 reference this appendix for their frame requirements.