Encyclopedia of Database Systems

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

Two-Poisson Model

  • Giambattista AmatiEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_920


Harter’s model; Probabilistic model of indexing


The 2-Poisson model is a mixture, that is a linear combination, of two Poisson distributions:
$$ \begin{array}{ll} \mathrm{Prob}\left(\mathrm{X}=\mathbf{tf}\right) &=\alpha\frac{\lambda^{\mathbf{tf}}{e}^{-\lambda }}{\mathbf{tf}!}\\ {}&+\left(1-\alpha \right)\frac{\mu^{\mathbf{tf}}{e}^{-\mu}}{\mathbf{tf}!}\quad \left[0\le \alpha \le 1\right] \end{array} $$
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Copyright information

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

Authors and Affiliations

  1. 1.Fondazione Ugo BordoniRomeItaly

Section editors and affiliations

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