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综合项目：迷你搜索引擎
将倒排索引、BM25评分、基于相关性判定的评估以及二阶语义排序器整合成一个运行在渡轮航线语料库上的可用搜索引擎。
1. Capstone: A Mini Search Engine
Capstone: A Mini Search Engine
2. Index and score
Index and score
3. Second-order scoring
Second-order scoring
4. What you built, and what it still misses
What you built, and what it still misses
5. Why the index
A search engine serves millions of queries against millions of documents. What does the inverted index change about scoring a query, compared with scanning every document for every query?
6. Computing one idf term
BM25 uses the idf weight . In the capstone corpus documents, the term crossing appears in of them. What is its idf, to three decimal places?
7. Averaging precision at cutoff
Three queries each return a ranked top 3. The first query has 3 relevant documents in its top 3, the second has 2, and the third has 3. What is the mean P@3 over the three queries, to three decimal places?
8. Matching with zero shared words
In the capstone, the query cheap tickets and the document about discount fares share no words, yet second-order scoring ranks it inside the top 3. What connects them?
9. The failure that survives
A theatre review containing storm scene keeps displacing a genuine storm-delay notice in every stage of the capstone, lexical, semantic and hybrid. What kind of evidence would actually separate them?