Tree model guided (TMG) enumeration as the basis for mining frequent patterns from XML documents

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Association mining consists of two important problems, namely frequent patterns discovery and rule construction. The former task is considered to be a more challenging problem to solve. Because of its importance and application in a number of data mining tasks, it has become the focus of many studies. A substantial amount of research has gone into the development of efficient algorithms for mining patterns from large structured or relational data. Compared with the fruitful achievements in mining structured data, mining in the semi-structured world still remains at a preliminary stage. The most popular representative of the semi-structured data is XML. Mining frequent patterns from XML poses more challenges in comparison to mining frequent patterns from relational data because XML is a tree-structured data and has an ordered data context. Moreover, XML data in general is larger in data size due to richer contents and more meta-data. Dealing with XML, thus involves greater unprecedented complexity in comparison to mining relational data. Mining frequent patterns from XML can be recast as mining frequent tree structures from a database of XML documents. The increase of XML data and the need for mining semi-structured data has sparked a lot of interest in finding frequent rooted trees in forests. In this thesis, we aim to develop a framework to mine frequent patterns from XML documents. The framework utilizes a structure-guided enumeration approach, Tree Model Guided (TMG), for efficient enumeration of tree structure and it makes use of novel structures for fast enumeration and frequency counting. By utilizing a novel array-based structure, an embedded list (EL), the framework offers a simple sequencelike tree enumeration technique. The effectiveness and extendibility of the framework is demonstrated in that it can be utilized not only for enumerating ordered subtrees but also for enumerating unordered subtrees and subsequences. Furthermore, the framework tackles the unprecedented complexity in mining frequent tree-structured patterns by generating only valid candidates with non-zero frequency count and employing a constraint-driven approach. Our experimental studies comparing the proposed framework with the state-of-the-art algorithms demonstrate the effectiveness and the efficiency of the proposed framework.
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