课程名称︰资讯检索 课程性质︰图资系大三必修 课程教师︰唐牧群 开课学院：文学院 开课系所︰图资系 考试日期（年月日）︰98.12.15 考试时限（分钟）：150分钟 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : Here is an imaginary database that contains the following 5 documents: D1: "a dog barks at a cat and it fell from a tree" D2: "an ant watches ants on the bark of a tree" D3: "a dog watches another dog barks a cat" D4: "a dog barks at a cat watches another cat" D5: "the bark fell from the tree as an ant watches" (Terms in the stop-word list have been grayed out.) 1a. Calculate DF(Document Frequency) and IDF(Inverse Document Frequency) weight for each index term(simply use N/n without logarithm). 1b. Create an inverted file for the database where each cell contains the TF*IDF weight of each term in the documents(treat singulars and plurals as the same word stem). 1c. What will be the search results look like by a system based on Boolean and vector space model, respectively. To rank the search results using vector space model, first calculate relevance scores(inner product without document length normalization) and rank the documents accordingly. 1d. After the initial iteration, the user examines the results and marks D2, D5 as relevant, and D3 and D4 as non-relevant. Produce the new ranking using Rocchio's method where α=1.0 β=1.0 γ=1.0 2. Unlike data retrieval where perfect precision and recall are guaranteed, information retrieval is more of a trial-and-error process. What might be the possible causes behind the uncertainty of IR? 3. Define 4 of the following 5 concepts: a.SIP(Statistically Improbable Phrases) b.The "explode" function for PubMed search c.The "subheading" function for PubMed search d.Relevance feedback e."Building block" search strategy 4. From information behavior research we know that users' "information needs" or "search tasks" come in different shapes and sizes. List a few ways(two or more) by which users' information needs or search tasks can be categorized and comments on how users' needs or tasks might impact information retrieval. 5. How is interactive view of IR different from traditional view of IR? What doew it consider to be the most crucial component of IR process? Name one or two interactive IR inspired search techniques that we have talked about in the class. --

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