Discussion Class 2

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Discussion Class 2

• A Vector Space Model
• for Automated Indexing

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Discussion Classes
Format Question Ask a member of the class to
answer. Provide opportunity for others to
comment. When answering Stand up. Give your
name. Make sure that the TA hears it. Speak
clearly so that all the class can
hear. Suggestions Do not be shy at presenting
partial answers. Differing viewpoints are
welcome.
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Question 1 Reading a Research Paper

• Who are the authors of this paper? What is their
  background? Why did they write this paper?
• (b) When was the paper written? What has changed
  since then?
• (c) What journal was the paper published in? Who
  are the readers of this journal?
• (d) What hypothesis is examined in this paper?

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Question 2 Document Space
How does this diagram relate to the hypothesis?

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Question 3 Research Methodology

• (a) What were the stages of research followed in
  this paper?
• (b) What test data was used? Are the results
  sensitive to the data? How much confidence to
  you have in the results?
• (c) What is a "recall-precision graph"?

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Question 4 Weighting -- Term Frequency

• The paper examines the effect of term weighting
  on
• the space density of index terms.
• (a) Why is this of interest in information
  retrieval?
• (b) What form of term frequency (tf) is used in
  this paper?
• (c) How does this form of term frequency differ
  from the standard form discussed in class? Is
  this difference significant?

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Question 5 Weighting -- Document Frequency
How is (inverse) document frequency used in this
paper?
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Question 6 Discrimination Value Model
Explain the following expression, which the
authors use to measure the space density.
n i1
Q ? s(C, Di)
Explain the following expression, which the
authors use to measure the contribution of term k
to the space density.
DVk Qk - Q
What does this tell about the discriminant value
of term k?
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Question 7

Question 7 Discuss this graph
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Question 8