Sequential Pattern Mining with Wildcards

Sequential pattern mining is an important research task in many domains, such as biological science. In this paper, we study the problem of mining frequent patterns from sequences with wildcards. The user can specify the gap constraints with flexibility. Given a subject sequence, a minimal support threshold and a gap constraint, we aim to find frequent patterns whose supports in the sequence are no less than the given support threshold. We design an efficient mining algorithm MAIL that utilizes the candidate occurrences of the prefix to compute the support of a pattern that avoids the rescanning of the sequence. We present two pruning strategies to improve the completeness and the time efficiency of MAIL. Experiments show that MAIL mines 2 times more patterns than one of its peers and the time performance is 12 times faster on average than its another peer.