Proposal: URML (substrate-neutral robot intent) Layer-3 → BehaviorTree.CPP as a typed-intent compilation target

[idoco2003]

Hi @BehaviorTree team,

Proposing a URML v0.1 capability-manifest mapping for BehaviorTree.CPP over BehaviorTree/BehaviorTree.CPP. URML (Apache-2.0) is a substrate-neutral spec for robot intent: typed primitive vocabulary + Layer-3 behavior composition + capability manifest + static validator.

This is URML's first robot-command-library RFC. URML's Layer-3 (behavior composition) needs a substrate to compile down to; BehaviorTree.CPP is the dominant C++ choice in ROS 2 and standalone robotics, and the architectural mapping is direct — URML primitives become custom TreeNode subclasses, Layer-3 composition becomes BT XML. The "URML the typed-intent language → BT the executable graph → Groot the visualizer" pipeline gives URML programs the BT tooling ecosystem for free.

This is proposal-only, part of URML's Move #12 outreach (16 RFCs covering speech / translation / robot-command-library substrates for URML's NL layer).

Full RFC with manifest mapping, four alternatives, and the BT-XML schema-versioning discussion: https://github.com/URML-MARS/URML/blob/main/docs/rfcs/0160-behaviortree-cpp-outreach.md

Questions worth maintainer input on:

1. Behavior-tree-runtime declaration shape. Is behaviortree_cpp the right slug for URML's manifest, or do you prefer a different convention?
2. BT XML schema version. Which schema version (3.x vs. 4.x) should URML's v0.1 compilation target? Is there a forward-looking version you'd recommend pinning to?
3. Custom-node registry declaration. URML compilation produces custom BT nodes (one per URML primitive). Is the manifest's enumerated registry the right shape?
4. Groot 2 boundary. URML's manifest declares the BehaviorTree.CPP runtime, not Groot 2 (separate concern, different license). Should URML's documentation explicitly distinguish the open-source runtime from the commercial-tier editor?
5. Adapter home. URML-side compiler in reference/bt-bridge/, contributed example in BehaviorTree.CPP/examples/, or external bridge repo?
6. Anything else.

Ido Yahalomi (URML maintainer, urml.dev, greenvh@gmail.com)

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