I remember reading about a kind of Graph data structure, where every change to the the graph could be preserved. I don't remember exactly neither the name, neither a good description (if it was the graph that remembered the changes, or each node who kept the changes of its childs).
It was on Wikipedia about 2-1.5 years ago, I was reading about version control. I would really appreciate if someone could help me find the name of this data sctructure.
Thanks Fraser, the paper is J. R. Driscoll, N. Sarnak, D. D. Sleator, R. E. Tarjan, Making Data Structures Persistent, Journal of Computer and System Sciences, Vol. 38, No. 1, 1989.