DATA_SCHEMA.md

Data schema

Row semantics

One Parquet row is one complete trajectory. All arrays with leading dimension T share the row's ordered trajectory time axis.

Top-level fields

Field	Type	Meaning
trajectory_id	string	stable public ID, traj_########
frame_rate_hz	float32	inverse median interval of timestamps_s
num_frames	int32	shared time dimension T
action_label	nullable string	action/gesture label
timestamps_s	list, T	trajectory-relative timestamps
hands	list	active hands; reserved empty source slots are removed
objects	list	rigid object trajectories
contacts	list<list>, T	zero or more contacts for every frame

HandTrajectory

Field	Shape	Unit / representation
hand_id	scalar	row-local ID
side	scalar	right
mano_shape	[10]	MANO beta vector
global_position_world_m	[T,3]	metres, world coordinates
global_rotation_world_rotvec_rad	[T,3]	axis-angle rotation vector, radians
mano_pose_rotvec_rad	[T,48]	MANO axis-angle pose, radians
joint_positions_world_m	[T,21,3]	metres, SNAP/manotorch joint order
urdf_dof	[T,28]	6 floating-base + 22 finger DoF
urdf_dof_target	[T,28]	controller target in the same DoF order

The 28-DoF order is:

ARTx, ARTy, ARTz, ARRx, ARRy, ARRz,
j1_thumb_cmc_abd, j1_thumb_cmc_flex, j1_thumb_cmc_twist,
j1_thumb_mcp_flex, j1_thumb_mcp_abd, j1_thumb_ip,
j2_index_mcp_abd, j2_index_mcp_flex, j2_index_pip, j2_index_dip,
j3_middle_mcp_abd, j3_middle_mcp_flex, j3_middle_pip, j3_middle_dip,
j4_ring_mcp_abd, j4_ring_mcp_flex, j4_ring_pip, j4_ring_dip,
j5_pinky_mcp_abd, j5_pinky_mcp_flex, j5_pinky_pip, j5_pinky_dip

The recorded 21 positions are 16 MANO/URDF keypoints followed by five fingertips:

palm,
index_mcp, index_pip, index_dip,
middle_mcp, middle_pip, middle_dip,
ring_mcp, ring_pip, ring_dip,
pinky_mcp, pinky_pip, pinky_dip,
thumb_cmc, thumb_mcp, thumb_ip,
thumb_tip, index_tip, middle_tip, ring_tip, pinky_tip

ObjectTrajectory

Field	Shape	Unit / representation
object_id	scalar	row-local ID
category	scalar	object category used by assets/manifest.json
position_world_m	[T,3]	metres, world coordinates
rotation_world_rotvec_rad	[T,3]	axis-angle rotation vector, radians

Contact

contacts[t] is empty when frame t has no contact. Each contact contains:

• row-local hand_id and object_id foreign keys;
• joint_name;
• total force vectors in world, joint, object, and optionally wrist coordinates;
• one or more contact points containing normal force and positions.

Wrist-coordinate fields are nullable. Null means the source contract did not provide that representation; it does not mean a zero vector.

Invariants

len(timestamps_s) == num_frames
len(contacts) == num_frames
len(each hand time-series field) == num_frames
len(each object time-series field) == num_frames
timestamps_s[t + 1] > timestamps_s[t]

Every contact references a hand and object in the same row. Fixed vector dimensions are encoded in Arrow and preserved through Parquet.

Schema version

Parquet Arrow metadata contains:

release_schema = hand_object_contact_trajectory
release_schema_version = 1.0.0
row_semantics = one complete trajectory per row