Is the frame of reference of the state of each body part/limb/node absolute or relative?

[jamesheald]

Is the state (cartesian position, cartesian velocity, quaternion, angular velocity) of each body part/limb/node of the agent defined with respect to the same fixed/world frame of reference (shared by all body parts/limbs/nodes) or with respect to a relative frame of reference (e.g. relative to the frame of reference of the parent or root body part/limb/node)?