Abstract: A value is assigned to a rate threshold for adding child nodes to a distinct parent node in a tree data structure. A first datum comprising a first variable assigned a first value and a second variable assigned a first value is added to the tree at a first timestamp, by adding to the first level in the tree a first parent node representing the first variable assigned the first value and adding to the second level in the tree a first child node representing the second variable assigned the first value and connected by a first directed edge from the first parent node. A second datum comprising the first variable assigned the first value and the second variable assigned a second value is received at a second timestamp. The method blocks adding to the second level in the tree a second child node representing the second variable assigned the second value and connected by a second directed edge from the first parent node when a rate based on the first timestamp and the second timestamp exceeds the rate threshold.