In recent years, I proposed three new kinds of data structure to represent itemsets. They are Node-list [1], N-list [2], and Nodeset [3]. They use prefix-tree nodes to represent itemsets instead of the set of tranaction ids.

Since prefix-tree is usually high compressed, Node-list [1], N-list [2], and Nodeset [3] are much shorten than Tidset or diffset, which are two classical vertical representatnion of itemsets. Therefore, for frequent itemset mining, the algorithms based on Node-list,…