A new method for version controlling of a tree structure is presented, The key feature of the method is that the latest state of a tree is retained and other versions are constructed from it on request, and information on the change history of a node is maintained in its parent node. Several algorithms for efficient manipulation of the tree have been developed, and it has been demonstrated that they correctly manipulate the tree, The performance of these algorithms has been compared with those of other tree-based methods, and found to be nearly optimal in all aspects of the comparison. (C) 1997 by John Wiley & Sons, Ltd.