隨著網路與資訊科技的高速發展，越來越多的資訊以文字文件的型態出現在網路上。資訊擷取(Information Retrieval) 指的是依使用者所下的查詢語句將相關連的文章傳回給使用者。而字詞使用差異(Word Mismatch)對於資訊擷取是一項挑戰，字詞使用差異指的是使用者使用和文件中不同的關鍵詞來描述同一概念的情況，查詢擴展即是一個處理字詞使用差異的方法。

因此在本篇論文中，我們提出一個模糊群集式字詞擴展技術(Fuzzy Cluster-Based Query Expansion Technique)來解決字詞使用差異，並利用現存的字詞擴展技術 (也就是Global Analysis and Cluster-Based Query Expansion Technique)當做我們的衡量基準。根據實證的結果，我們發現模糊群集式字詞擴展技術則可以提供比現存字詞擴展技術較精確的查詢結果。

Advances in information and network technologies have fostered the creation and availability of a vast amount of online information, typically in the form of text documents. Information retrieval (IR) pertains to determining the relevance between a user query and documents in the target collection, then returning those documents that are likely to satisfy the user’s information needs. One challenging issue in IR is word mismatch, which occurs when concepts can be described by different words in the user queries and/or documents. Query expansion is a promising approach for dealing with word mismatch in IR.

In this thesis, we develop a fuzzy cluster-based query expansion technique to solve the word mismatch problem. Using existing expansion techniques (i.e., global analysis and non-fuzzy cluster-based query expansion) as performance benchmarks, our empirical results suggest that the fuzzy cluster-based query expansion technique can provide a more accurate query result than the benchmark techniques can.

CHAPTER 1 . INTRODUCTION 1
1.1 Background 1
1.2 Research Motivation and Objectives 4
1.3 Organization of the Thesis 5
CHAPTER 2 . LITERATURE REVIEW 6
2.1 Query Expansion Methods 6
2.1.1 Global analysis 6
2.1.2 Local feedback 7
2.1.3 Non-fuzzy cluster-based query expansion techniques 8
2.2 Thesaurus Construction Techniques 10
2.3 Document Clustering 14
2.4 Fuzzy Clustering and Fuzzy Document Clustering 16
CHAPTER 3 . DEVELOPMENT OF A FUZZY CLUSTER-BASED QUERY EXPANSION TECHNIQUE 19
3.1 Process of the Fuzzy Cluster-Based Query Expansion Technique 19
3.2 Thesauri Construction Process 20
3.2.1 Fuzzy document clustering 21
3.2.2 Local thesaurus construction 26
3.3 Query Process 27
3.3.1 Local query expansion 28
3.3.2 Document retrieval 29
CHAPTER 4 . EMPIRICAL EVALUATION 31
4.1 Data Collection 31
4.2 Evaluation Procedure and Criteria 34
4.3 Benchmark Techniques 38
4.4 Evaluation Results 40
4.4.1 Effects of number of document clusters 42
4.4.2 Comparative evaluation 43
4.4.3 Effects of the number of query terms 44
CHAPTER 5 . CONCLUSIONS AND FUTURE RESEARCH DIRECTIONS 49
REFERENCES 51
APPENDIX A: CANDIDATE TERMS FOR INFORMATION RETRIEVAL 55
APPENDIX B: INTERSECTION INFORMATION 61

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