Fig xA The N lists of frequent items in

A transaction database.IDItemsOrdered frequent items1a, f, ga, f2a, b, c, eb, c, e, a3b, c, e, ib, c, e4b, c, e, hb, c, e5b, c, d, e, fb, c, e, fFull-size tableTable optionsView in workspaceDownload as CSV
Fig. 1 shows the PPC-tree resulting from Example 1. The TIC10 with (3, 6) means that its pre-order is 3, post-order is 6, the item-name is b, and count is 4.Definition 3 PP-code.
For each node N   in a PPC-tree, we call 〈(N.pre-order,N.post-order):count〉〈(N.pre-order,N.post-order):count〉 the PP-code of N.Definition 4 the N-list of frequent item.
Given a PPC-tree, the N-list of a frequent item is spindle apparatus a sequence of all the PP-codes of nodes registering the item in the PPC-tree. The PP-codes are arranged in an ascending order of their pre-order values.
Fig. 1. The PPC-tree resulting from Example 1.Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 2 shows the N-lists of all frequent items in Example 1.Definition 5 ?? relation.