A machine learning subfield called “learning to” do this task uses normalized discounted cumulative gain as a metric for evaluating it. For 10 points each:
[10m] Name this information retrieval task. Search engines use an algorithm for this task that computes the principal eigenvector of the transition matrix of a webgraph.
ANSWER: ranking [accept PageRank; accept learning to rank]
[10h] When ranking based on a vector space model, this statistic is usually used for a vector’s components. This statistic is a product of two terms: one that represents how common a word is in a document, and another that represents how rare a word is in a corpus.
ANSWER: tf–idf [or term frequency–inverse document frequency]
[10e] Ranking documents by relevance improves on information retrieval models using this algebra system, which computes truth values using logical operators.
ANSWER: Boolean algebra [or Boolean logic; accept Boolean model or Boolean query]
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