The current state is connected to previous states using a set of 7 distinct relationships defined in terms of each state's parser configuration, which includes of a stack and a queue.
the current state is related to the last previous state whose parser configuration has: the same queue, the same stack, a stack top which is the rightmost right child of the current stack top, a stack top which is the leftmost left child of the current stack top, a front of the queue which is the leftmost child of the front of the current queue, a stack top which is the head word of the current stack top, a front of the queue which is the current stack top.