Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

Rocchio’s Formula

Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_932


Rocchio’s formula is used to determine the query term weights of the terms in the new query when Rocchio’s relevance feedback algorithm is applied.

Key Points

In 1971, Rocchio proposed a classical query expansion algorithm based on the Vector Space model [ 1]. The basic algorithm assumes that the user identifies a set R of relevant documents and a set N of non relevant documents and the improved query is the result of a linear combination of the mean frequencies tf of the terms in the original query and in these two sets ( the centroids of R and N), that is the weight of each term in the new query is:
$$ qt\;{f}_m=\alpha . qtf+\beta .\sum_{d\in R} tf-\gamma .\sum_{d\in N} tf $$
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Recommended Reading

  1. 1.
    Rocchio J. Relevance feedback in information retrieval. Englewood Cliffs: Prentice-Hall; 1971. p. 313–23.Google Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.University of GlasgowGlasgowUK

Section editors and affiliations

  • Giambattista Amati
    • 1
  1. 1.Fondazione Ugo BordoniRomeItaly