So a node can be of type=NODE or type=JOINT.
For an importer I am using type=JOINT to create a specific bone class when traversing the <visual_scene>.
However it also seems to be allowed to specify nodes of type=NODE and refer to them in the joints array (example TurbochiFromXSI.dae).
It even seems to be allowed to build a joint hierarchy with nodes of type=JOINT and type=NODE mixed (astroBoy_walk.dae).
So what is the use of specifying type=JOINT for a node?