STRUCTURAL DESCRIPTION
URDF answers foundational questions extremely well.
URDF is an XML robot description format centered on links and joints. It represents the robot model as a tree and can encode topology, inertial properties, joint limits, origins, dynamics and related structural information.
Those facts are foundational. They answer questions such as: what is connected to what, how can it move, what are the limits, and what physical properties were authored?
SCENE + PHYSICS
OpenUSD can represent richer composed worlds and physics.
UsdPhysics extends the OpenUSD scene graph with rigid bodies, joints, collision and simulation-oriented properties. It is useful for complex scenes and physically meaningful simulation assets.
OpenRGD does not attempt to replace the OpenUSD composition engine. Its current lightweight USDA importer intentionally supports only a narrow, auditable subset and refuses to pretend it has resolved semantics that require the full SDK.
THE SEMANTIC GAP
Structure alone does not tell an AI what the body means operationally.
Identity
Which physical robot or profile does this description belong to?
Capability
What tasks and actions are explicitly declared or supported?
Operational limits
What boundaries apply beyond raw joint ranges?
Safety context
Which constraints must remain explicit before execution?
Provenance
Which facts came from source evidence, calibration or later enrichment?
Lifecycle
How has the effective embodiment changed over time?
OPENRGD IMPORT
Extract evidence. Do not manufacture missing knowledge.
OpenRGD imports only source-supported Foundation evidence from supported URDF and USDA inputs. Missing values remain missing. Import does not create identity, safety policy, alignment, cognition, HAL bindings or hardware authorization.
KEY PRINCIPLE
A description is evidence, not permission.
Even a complete structural description cannot prove that a robot is safe to operate or that a controller is correctly bound to hardware. OpenRGD preserves that distinction deliberately.