Semantic-based pruning of redundant and uninteresting frequent geographic patterns

In geographic association rule mining many patterns are either redundant or contain well known geographic domain associations explicitly represented in knowledge resources such as geographic database schemas and geo-ontologies. Existing spatial association rule mining algorithms are Apriori-like, and therefore generate a large amount of redundant patterns. For non-spatial data, the closed frequent pattern mining technique has been introduced to remove redundant patterns. This approach, however, does not warrant the elimination of both redundant and well known geographic dependences when mining geographic databases. This paper presents a novel method for pruning both redundant and well known geographic dependences, by pushing semantics into the pattern mining task. Experiments with real geographic databases have demonstrated a significant reduction of the total amount of patterns and the efficiency of the method.     

利用模式指导树的并行频繁项集挖据方法

关联规则挖掘的主要任务是根据对事务的统计找出项之间的关系。传统的挖掘算法要求项具有逻辑属性,并在挖掘过程中产生大量的中间项集,成为算法的瓶颈。给出一种基于关联路径树的表格数据组织形式,并采用模式指导的方式进行频繁项集挖掘,该方法不要求项具有逻辑属性,初始模式不同的项集组合迭代可以分配到不同的CPU完成,提高了算法的执行效率。该算法对美国1984年国会选举数据进行了实验,结果完全正确。     

On the adaptability of G3PARM to the extraction of rare association rules

To date, association rule mining has mainly focused on the discovery of frequent patterns. Nevertheless, it is often interesting to focus on those that do not frequently occur. Existing algorithms for mining this kind of infrequent patterns are mainly based on exhaustive search methods and can be applied only over categorical domains. In a previous work, the use of grammar-guided genetic programming for the discovery of frequent association rules was introduced, showing that this proposal was competitive in terms of scalability, expressiveness, flexibility and the ability to restrict the search space. The goal of this work is to demonstrate that this proposal is also appropriate for the discovery of rare association rules. This approach allows one to obtain solutions within specified time limits and does not require large amounts of memory, as current algorithms do. It also provides mechanisms to discard noise from the rare association rule set by applying four different and specific fitness functions, which are compared and studied in depth. Finally, this approach is compared with other existing algorithms for mining rare association rules, and an analysis of the mined rules is performed. As a result, this approach mines rare rules in a homogeneous and low execution time. The experimental study shows that this proposal obtains a small and accurate set of rules close to the size specified by the data miner.     

A framework for regional association rule mining and scoping in spatial datasets

The motivation for regional association rule mining and scoping is driven by the facts that global statistics seldom provide useful insight and that most relationships in spatial datasets are geographically regional, rather than global. Furthermore, when using traditional association rule mining, regional patterns frequently fail to be discovered due to insufficient global confidence and/or support. In this paper, we systematically study this problem and address the unique challenges of regional association mining and scoping: (1) region discovery: how to identify interesting regions from which novel and useful regional association rules can be extracted; (2) regional association rule scoping: how to determine the scope of regional association rules. We investigate the duality between regional association rules and regions where the associations are valid: interesting regions are identified to seek novel regional patterns, and a regional pattern has a scope of a set of regions in which the pattern is valid. In particular, we present a reward-based region discovery framework that employs a divisive grid-based supervised clustering for region discovery. We evaluate our approach in a real-world case study to identify spatial risk patterns from arsenic in the Texas water supply. Our experimental results confirm and validate research results in the study of arsenic contamination, and our work leads to the discovery of novel findings to be further explored by domain scientists.     

Finding hot query patterns over an XQuery stream

Caching query results is one efficient approach to improving the performance of XML management systems. This entails the discovery of frequent XML queries issued by users. In this paper, we model user queries as a stream of XML query pattern trees and mine the frequent query patterns over the query stream. To facilitate the one-pass mining process, we devise a novel data structure called DTS to summarize the pattern trees seen so far. By grouping the incoming pattern trees into batches, we can dynamically mark the active portion of the current batch in DTS and limit the enumeration of candidate trees to only the currently active pattern trees. We also design another summary data structure called ECTree that provides for the incremental computation of the frequent tree patterns over the query stream. Based on the above two constructs, we present two mining algorithms called XQSMinerI and XQSMinerII. XQSMinerI is fast, but it tends to overestimate, while XQSMinerII adopts a filter-and-refine approach to minimize the amount of overestimation. Experimental results show that the proposed methods are both efficient and scalable and require only small memory footprints.Received: 17 October 2003, Accepted: 16 April 2004, Published online: 14 September 2004Edited by: J. Gehrke and J. Hellerstein.     

Incremental sequence-based frequent query pattern mining from XML queries

Existing algorithms of mining frequent XML query patterns (XQPs) employ a candidate generate-and-test strategy. They involve expensive candidate enumeration and costly tree-containment checking. Further, most of existing methods compute the frequencies of candidate query patterns from scratch periodically by checking the entire transaction database, which consists of XQPs transferred from user query logs. However, it is not straightforward to maintain such discovered frequent patterns in real XML databases as there may be frequent updates that may not only invalidate some existing frequent query patterns but also generate some new frequent query patterns. Therefore, a drawback of existing methods is that they are rather inefficient for the evolution of transaction databases. To address above-mentioned problems, this paper proposes an efficient algorithm ESPRIT to mine frequent XQPs without costly tree-containment checking. ESPRIT transforms XML queries into sequences using a one-to-one mapping technique and mines the frequent sequences to generate frequent XQPs. We propose two efficient incremental algorithms, ESPRIT-i and ESPRIT-i ⁺, to incrementally mine frequent XQPs. We devise several novel optimization techniques of query rewriting, cache lookup, and cache replacement to improve the answerability and the hit rate of caching. We have implemented our algorithms and conducted a set of experimental studies on various datasets. The experimental results demonstrate that our algorithms achieve high efficiency and scalability and outperform state-of-the-art methods significantly.     

Efficient Mining of Frequent Closed XML Query Pattern

Previous research works have presented convincing arguments that a frequent pattern mining algorithm should not mine all frequent but only the closed ones because the latter leads to not only more compact yet complete result set but also better efficiency. Upon discovery of frequent closed XML query patterns, indexing and caching can be effectively adopted for query performance enhancement. Most of the previous algorithms for finding frequent patterns basically introduced a straightforward generate-and-test strategy. In this paper, we present SOLARIA＊, an efficient algorithm for mining frequent closed XML query patterns without candidate maintenance and costly tree-containment checking. Efficient algorithm of sequence mining is involved in discovering frequent tree-structured patterns, which aims at replacing expensive containment testing with cheap parent-child checking in sequences. SOLARIA＊ deeply prunes unrelated search space for frequent pattern enumeration by parent-child relationship constraint. By a thorough experimental study on various real-life data, we demonstrate the efficiency and scalability of SOLARIA＊ over the previous known alternative. SOLARIA＊ is also linearly scalable in terms of XML queries＇ size.     

Scalable algorithms for association mining

Association rule discovery has emerged as an important problem in knowledge discovery and data mining. The association mining task consists of identifying the frequent itemsets, and then forming conditional implication rules among them. We present efficient algorithms for the discovery of frequent itemsets which forms the compute intensive phase of the task. The algorithms utilize the structural properties of frequent itemsets to facilitate fast discovery. The items are organized into a subset lattice search space, which is decomposed into small independent chunks or sublattices, which can be solved in memory. Efficient lattice traversal techniques are presented which quickly identify all the long frequent itemsets and their subsets if required. We also present the effect of using different database layout schemes combined with the proposed decomposition and traversal techniques. We experimentally compare the new algorithms against the previous approaches, obtaining improvements of more than an order of magnitude for our test databases     

基于数据融合的知识发现方法在网络管理中的应用

提出用于网络管理的基于数据融合的知识发现系统框架，研究数据融合技术在知识发现的数据准备和预处理阶段的应用，研究关联规则在表达网络管理知识方面的适用性并针对网络管理数据时序性的特点，引入情景规则来表示期望发掘的知识，指出网络故障管理中关联规则和情景规则的挖掘算法以及知识增量式更新的算法，并简介了原型系统的实现方法。     

Levelwise Search and Pruning Strategies for First-Order Hypothesis Spaces

The discovery of interesting patterns in relational databases is an important data mining task. This paper is concerned with the development of a search algorithm for first-order hypothesis spaces adopting an important pruning technique (termed subset pruning here) from association rule mining in a first-order setting. The basic search algorithm is extended by so-called requires and excludes constraints allowing to declare prior knowledge about the data, such as mutual exclusion or generalization relationships among attributes, so that it can be exploited for further structuring and restricting the search space. Furthermore, it is illustrated how to process taxonomies and numerical attributes in the search algorithm.Several task settings using different interestingness criteria and search modes with corresponding pruning criteria are described. Three settings serve as test beds for evaluation of the proposed approach. The experimental evaluation shows that the impact of subset pruning is significant, since it reduces the number of hypothesis evaluations in many cases by about 50%. The impact of generalization relationships is shown to be less effective in our experimental set-up.     

数据流中一种快速启发式频繁模式挖掘方法

在现有的数据流频繁模式挖掘算法中,批处理方法平均处理时间短,但需要积攒足够的数据,使得其实时性差且查询粒度粗;而启发式方法可以直接处理数据流,但处理速度慢.提出一种改进的字典树结构--IL-TREE(improved lexicographic tree),并在其基础上提出一种新的启发式算法FPIL-Stream(frequent pattem mining based on improved lexicographic tree),在更新模式和生成新模式的过程中,可以快速定位历史模式.算法结合了倾斜窗口策略,可以详细记录历史信息.该算法在及时处理数据流的前提下,也降低了数据的平均处理时间,并且提供了更细的查询粒度.     

序列模式增量式更新的研究

序列模式挖掘是数据挖掘领域中十分重要的研究课题.目前已有许多算法用于序列模式的挖掘,但在序列模式增量式更新方面的研究还比较少,针对这种情况提出了序列模式增量式更新的挖掘算法SPIU.SPIU算法充分利用了原有的挖掘结果,并对产生的候选频繁序列进行剪枝,有效地减小了候选频繁序列的大小,从而很好地改善了挖掘效率.测试结果表明SPIU算法是正确和高效的,另外算法还具有很好的扩放性.     

挖掘空间关联规则的前缀树算法设计与实现

空间关联规则挖掘是在空间数据库中进行知识发现的一类重要问题．为此提出了挖掘空间关联规则的二阶段策略，通过多轮次单层布尔型关联规则挖掘，自顶向下逐步细化空间谓词的粒度，从而空间谓词的计算量大大减少．同时，设计了一种基于前缀树的单层布尔型关联规则挖掘算法(FPT-Generate)，不需要反复扫描数据库，不产生候选模式集，并在关键优化技术上取得了突破．实验表明，以FPT-Generate为挖掘引擎的空间关联规则发现系统的时间效率与空间可伸缩性远远优于以经典算法Apriori为引擎的系统。     

一种无阈值的频繁模式生成算法

在数据挖掘的关联规则挖掘算法中,传统的频繁模式挖掘算法需要用户指定项集的最小支持度。引入Top-k模式挖掘概念的改进算法虽然无需指定最小支持度,但仍需指定阈值k。针对上述问题,对传统挖掘算法进行改进,提出一种新的频繁模式挖掘算法(TNFP- growth)。该算法无需指定最小支持度或阈值,按照支持度降序排列进行模式挖掘,有序地返回频繁模式给用户。实验结果证明,该算法的执行效率更高,具有更强的伸缩性。     

序列模式图及其构造算法

序列模式挖掘是数据挖掘的一个重要分支。在序列事务及有关信息处理中有着广泛的应用,目前已有许多序列模式模型及相应的挖掘算法，该文在对序列模式挖掘问题及挖掘算法进行分析的基础上。定义了一种称为序列模式图的序列模式框架。用于表示序列模式挖掘过程发现的所有序列模式，序列模式图是由离散状态的序列集到统一的图结构的桥梁，可以将序列模式挖掘结果统一到序列模式图中来，基于序列模式图进行研究可发现某些结构化的新知识，称之为后序列模式挖掘，文中还给出了序列模式图的有关性质及构造算法。     

一种基于频繁模式树的约束最大频繁项目集挖掘及其更新算法

目前已提出了许多快速的关联规则挖掘算法,实际上用户只关心部分关联规则,如他们仅想知道包含指定项目的规则．当这些约束被用于数据预处理或将它结合到数据挖掘算法中去时,可以显著减少算法的执行时间．为此,考虑了一类包含或不包含某些项目的布尔表达式约束条件,提出了一种快速的基于FP—tree的约束最大频繁项目集挖掘算法CMFIMA,并对其更新问题进行了研究,提出了一种增量式更新约束最大频繁项目集挖掘算法CMFIUA．     

频繁项集挖掘的研究进展及主流方法

关联分析作为数据挖掘的主要研究模块之一,主要用于发现隐藏在大型数据集中的强关联特征。而多数关联规则挖掘任务可分为频繁模式(频繁项集、频繁序列、频繁子图)的产生和规则的产生。前者发现数据集中满足最小支持度阈值的项集、序列与子图;后者从上一步发现的频繁模式中提取高置信度的规则。频繁项集挖掘是许多数据挖掘任务中的关键问题,也是关联规则挖掘算法的核心。十几年来,学者们致力于提高频繁项集的生成效率,从不同的角度进行改进以提高算法效率,大量的高效可伸缩性算法被提出。文中对频繁项集挖掘进行深入分析,对完全频繁项集、闭频繁项集、极大频繁项集的典型算法进行介绍和评述,最后对频繁项集挖掘算法的研究方向进行简要分析。     

A stock recommendation system exploiting rule discovery in stock databases

This paper addresses an approach that recommends investment types to stock investors by discovering useful rules from past changing patterns of stock prices in databases. First, we define a new rule model for recommending stock investment types. For a frequent pattern of stock prices, if its subsequent stock prices are matched to a condition of an investor, the model recommends a corresponding investment type for this stock. The frequent pattern is regarded as a rule head, and the subsequent part a rule body. We observed that the conditions on rule bodies are quite different depending on dispositions of investors while rule heads are independent of characteristics of investors in most cases. With this observation, we propose a new method that discovers and stores only the rule heads rather than the whole rules in a rule discovery process. This allows investors to impose various conditions on rule bodies flexibly, and also improves the performance of a rule discovery process by reducing the number of rules to be discovered. For efficient discovery and matching of rules, we propose methods for discovering frequent patterns, constructing a frequent pattern base, and its indexing. We also suggest a method that finds the rules matched to a query from a frequent pattern base, and a method that recommends an investment type by using the rules. Finally, we verify the effectiveness and the efficiency of our approach through extensive experiments with real-life stock data.     

XML data mining

With the spreading of XML sources, mining XML data can be an important objective in the near future. This paper presents a project focussed on designing a general‐purpose query language in support of mining XML data. In our framework, raw data, mining models and domain knowledge are represented by way of XML documents and stored inside native XML databases. Data mining (DM) tasks are expressed in an extension of XQuery. Special attention is given to the frequent pattern discovery problem, and a way of exploiting domain‐dependent optimizations and efficient data structures as deeper as possible in the extraction process is presented. We report the results of a first bunch of experiments, showing that a good trade‐off between expressiveness and efficiency in XML DM is not a chimera. Copyright © 2009 John Wiley & Sons, Ltd.