信息检索与搜索引擎ppt课件.pptx

信息检索与搜索引擎Introduction to Information RetrievalGESC1007
Philippe Fournier-Viger
Full professor
School of Natural Sciences and Humanities
******@
Spring 2021
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Last week
We have discussed:
A complete search system
Today:
Brief review of last week
Evaluation in an information retrieval system
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Course schedule (日程安排)
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Week 1
Introduction (Chapter 1)
Boolean retrieval
Week 2
Term vocabulary and posting lists (Chapter 2)
Week 3
Dictionaries and tolerant retrieval (Chapter 3)
Week 4
Index construction (Chapter 4)
Week 5
Scoring, term weighting, the vector space model (Chapter 6)
Week 6
A complete search system (Chapter 7)
Week 7
Evaluation in information retrieval
Week 8
Web search engines, advanced topics, conclusion
Final exam
LAST WEEK
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1) Initially, we have a set of documents.
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2)Linguistic processing is applied to these documents (tokenization, stemming, language detection…)
Each document is a set of terms.
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3) The IR System keeps a copy of each document in a cache (缓存).
This is useful to generate snippets (片段)
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Snippet: a short text that accompany each document in the result list of a search engine
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4) A copy of each document is given to indexers. These programs will create different kind of indexes: positional indexes, indexes for spell correction, structures for inexact retrieval….
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5) When a user searches using a free-text query, the query parser transforms the query, and spell-correction is applied.