ROS 2

A ROS 2 host is Rig when it emits entities with POD components keyed by schema ids it supports (honors). rmw, DDS, launch files, and bags are fulfillment - not this catalog.

Unlike OpenBIM, there is no rig.ros2.* layer. Portable meaning is spatial / I/O / sensor / SUDE. Product protocol names stay out of schema ids (same rule as rig.music.clock). ROS-only fields travel as x.ros2.* until a second speaker needs the same meaning in the catalog.

Map (existing ids only)

ROS 2 idea	Rig
TF frame	Entity with `rig.meta.named` + `rig.spatial.transform`
Parent frame	`rig.spatial.relationship` `parent`
URDF link	Same as TF; mesh / material compose as usual
Joint / constraint	Stay out - `rig.sim.rigidbody` already refuses shared constraint numbers
Graph member (ROS node)	Entity + `rig.meta.named`. Namespace, `domainId`, FQN stay `x.ros2.`. Do not call this a "host" (Rig host* = live program)
Topic / service / action	Named bus, like `rig.io.osc`. Message type strings and QoS stay `x.ros2.*`
Message payload	Land on existing fields in Update (`transform`, `rig.sim.rigidbody.velocity`, `rig.sensor.*`, `rig.pixel.source`) - do not catalog Twist / Image as schemas
`/clock`	SUDE `dt`. Do not reuse `rig.music.clock`
Camera stream	`rig.pixel.source` when it is capture; frames stay in the host
GPIO / occupancy	`rig.sensor.gpio` / `presence`; `device` may point at the node entity

World pose / TF lookup caches stay in the host - rebuild from local transform + parent, same as any scene graph.

Do not map ROS nodes onto rig.node.*. That catalog is an artist patcher (typeId = host behaviour). Different graph - see Grouping graphs (do not merge).

TF sketch

Two frames, existing schemas only:

{
  "entities": [
    {
      "id": "base_link",
      "components": {
        "rig.meta.named": { "name": "base_link", "stableId": "base_link" },
        "rig.spatial.transform": {
          "position": [0, 0, 0],
          "rotation": [0, 0, 0, 1],
          "scale": [1, 1, 1]
        }
      }
    },
    {
      "id": "camera_link",
      "components": {
        "rig.meta.named": { "name": "camera_link", "stableId": "camera_link" },
        "rig.spatial.transform": {
          "position": [0.1, 0, 0.2],
          "rotation": [0, 0, 0, 1],
          "scale": [1, 1, 1]
        },
        "rig.spatial.relationship": { "parent": "base_link" }
      }
    }
  ]
}

(Wrap in a full document with "rig" set to the current VERSION before validating.)

Stay out

Stay out	Why
DDS discovery / `ros2 node list`	Who is alive is a host cache - same class as a LAN scan table
QoS, last message, in-flight goals	Runtime state - do not serialize
Launch, bags, rmw vendor	Process graph and middleware are fulfillment
`rig.ros2.*`	Product protocol names stay out of schema ids

A scan of who is up is not Contract meaning. RigKit's x.rigkit.net_scan / x.rigkit.net_host stay host extensions.

Encodings (fulfillment)

Surface	Role
TF2 / URDF	Map frames and links into spatial transform + relationship
Topics / services / actions	Pub/sub and RPC in Update; write portable fields from payloads
`x.ros2.*`	Namespace, domain, message type, QoS - travel; do not port
Bags / launch	Replay and process graph stay in the host

Honest limit

Two hosts that speak transform + relationship + the sensors they share can exchange a robot pose tree as .rig. Round-tripping every ROS message type, QoS profile, and discovery snapshot is not required. A host that needs the rest keeps it in ROS and maps what it understands.