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Modern Information Retrieval

Modern Information Retrieval. 第三組 87070300 陳國富 87068800 王俊傑 87070600 夏希璿. Our Environment. CPU : Duron 700 RAM : 320MB OS : Microsoft XP Professional Database : Mysql Database Program Language : PHP Script Language Store Device : 30GB 7200rpm HardDisk. FrameWork. WWW. 文件. 讀取. 查詢.

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Modern Information Retrieval

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  1. Modern Information Retrieval 第三組 87070300 陳國富 87068800 王俊傑 87070600 夏希璿

  2. Our Environment • CPU : Duron 700 • RAM : 320MB • OS : Microsoft XP Professional • Database : Mysql Database • Program Language : PHP Script Language • Store Device : 30GB 7200rpm HardDisk

  3. FrameWork WWW 文件 讀取 查詢 回報 Index Processor DataBase Ranking Processor 檢索結果 儲存 圖表1:系統架構圖

  4. Indexing Processing 讀取文件 去除Stop Word 產生單字Weight 去除Weight過小的單字

  5. Indexing Processing(Cont.) 計算方式: Weight = Wn + loge(T/Ts) • Wn : index在該文章中出現的次數 • T :文章總數 • Ts :含有該index的文章總數 • 去除weight過小的index

  6. Indexing Processing(Cont.) • 舉例- • “Play” Weight : 5.965 • “Taiwan” Weight : 25.745 • “Stock” Weight : 13.922 • 每個index在不同文件中，其weight都不同

  7. Search & Ranking • 假設Query = (Q1 , Q2 ,Q3 …..Qn)為使用者輸入的檢索，n為Query的單字數目；(D1,D2,D3….Dm)為檢索出來的文章，m為檢索結果的數目 wij為Qi在Dj中的weight值 W j = Σ wij = 所有檢索在Dj中的weight總和 DOCW j = 在文章j 中，所有index的weight總和

  8. Search & Ranking(Cont.) • 依照下列來決定排名 • 文章中含有Query數目的多寡 • Query在該篇文章中所佔的比例重 = ( Wj / DOCWj ) • 文章的index weight總和( DOCWj ) • 當Query 單字 > 2時，才作為排名的依據

  9. Recall Precision 不使用文章加權 0% 44.50% 10% 29.03% 20.39% 20% 16.89% 30% 40% 15.10% 50% 12.47% 9.02% 60% 70% 6.20% 80% 4.35% 2.42% 90% 0.29% 100% Precision 使用文章加權 47.77% 28.80% 21.26% 17.10% 15.97% 12.79% 9.00% 6.29% 4.38% 2.58% 0.29% Search & Ranking(Cont.)

  10. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 用文章加權 38.16 16.78 10.03 7.18 6.45 3.97 3.05 2.43 1.99 0.97 0.01 無文章加權 32.39 17.17 8.52 6.82 4.96 3.43 3.04 2.27 1.97 0.69 0.01 Search & Ranking(Cont.)

  11. Recall 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Precision 61.22% 45.64% 36.99% 30.98% 29.30% 25.13% 17.34% 11.69% 7.73% 4.83% 0.68% Search & Ranking(Cont.)

  12. 結論 • 對於較長的Query 準確率較低 • 無法分析Query中的每個word • Query中每個Word的比重不一定相同 • “Actions Against International Terrorists” • 重點在於 “Against”及 “Terrorists”兩字 • Index的選擇

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