(Copying item from Bug 62 long list attachment, not yet implemeted.)
1. not sure where spring came from, but if its a rotational spring then its "torque" instead of "force" and torque is not measured in "degrees".
2. Explain what spring is for. Does it limit the torque or force the solver can apply to be proportional to the violation of the constraint? i.e. a joint soft limit?
3. Also, what its spring's "target value" child for. johns code parses target_value but doesn't pass it through. Is it meant to be the "rest length" of a spring?
For item #3, the schema says that target_value is "The spring's target or resting distance." "Distance" doesn't imply the same thing as "length" to me. What's the better phrasing?