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Mining frequent pattern has attracted much research interests (Han, et al., 2000; Han & Pei, 2004; Zaki et al., 1997) for a past decade because of its broad domain applications. The focal point of mining frequent pattern is to find the interesting relationships among set of items in the data repositories. Firstly, it was proposed by Agrawal et al. (1993) and still played important roles in knowledge discovery communities. Recently, more than hundreds of research papers have been published including new or modification of algorithms in order to resolve the problems of mining frequent pattern.
Association rule (Agrawal, et al., 1993) is a probabilistic statement about the co-occurrence of the data according to the if-then statement. One of the important components that are typically used in deriving the association rule is frequent patterns. Since both of them are closely interrelated; hence quite a number of studies have been performed heretofore (Abdullah et al., 2013; Herawan et al., 2013a; Herawan et al. 2013b; Abdullah et al., 2012a; Abdullah et al. 2012b; Herawan et al. 2012a; Herawan et al., 2012b; Herawan and Abdullah, 2012; Abdullah et al., 2011a; Abdullah et al., 2011b; Abdullah et al., 2011c; Veeramalai & Kannan, 2011; Ashrafi et al., 2005). In data mining, a set of items in pattern is also defined as an itemset. The itemset is said to be frequent, if it appears equal or exceed to the predefined minimum supports. The item (or itemset) support is defined as a probability of item (or itemset) occurs in the transaction. Besides that, confidence is another alternative measurement used in pair with support. The confidence is defined as a probability of the rule’s consequent that also contain the antecedent in the transaction. Association rules are said to be strong if it meets the minimum confidence.
The main problem in frequent pattern mining is to achieve an efficiency of managing the huge amount of data in computer's memory. As a result, frequent pattern tree (FP-Tree) (Han, et al., 2000) has become one of the alternative data structures to represent the vast transactional of database in a compressed manner. Several variations of constructing or updating the FP-Tree have been proposed and it can be categorized into multiple and single database scans. For the first category and including FP-Tree (Han, et al., 2000), the related studies are Adjusting FP-Tree for Incremental Mining (AFPIM) (Koh & Shieh, 2004) and Extending FP-tree for Incremental Mining (EPFIM) (Li, et al., 2006). The related researches in the second category are Compressed and Arranged Transaction Sequence (CATS) tree (Cheung & Zaïane, 2003), Branch Sorting Method (BSM) (Tanbeer, et al., 2009) and Batch Incremented Tree (BIT) (Totad, et al., 2010).
However, there are two major drawbacks encountered from the aforesaid studies. Firstly, the construction of FP-Tree is still based on extracting the patterns that fulfils the support threshold from the semi structured of its original databases. Secondly, if the existing databases are updated, the current FP-Tree must be rebuilt from the beginning because of the changes in items and patterns supports. In some research extensions, the structure of FP-Tree will be reorganized with extensive modification operations (deletion and insertion) due to additional transactions in databases. In fact, computational extensive in constructing FP-Tree is still an obstacle or outstanding issues in efficiently mining frequent patterns.