I know that each joint has his own the inverse binding matrix. But in the Collada format in the element "controller" there are inverse binding matrices for each bone in this element. But a bone could be in different controllers several times. And the inverse binding matrices of this bone in each of this controllers must be the same. Is it correct or there are other circumstances which are influencing to this matrices? If there aren`t than it is a simple repetition and an information redundancy in the Collada files.