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From "Clemens Marschner" <c...@lanlab.de>
Subject Lucene's Ranking Function
Date Wed, 11 Sep 2002 10:52:29 GMT

In the FAQ it reads

 score_d = sum_t(tf_q * idf_t / norm_q * tf_d * idf_t / norm_d_t * boost_t)
* coord_q_d


1. I think the new document boost is missing, isn't it?
With that it should be something like

 score_d = sum_t(tf_q * idf_t / norm_q * tf_d * idf_t / norm_d_t * boost_t)
* coord_q_d * boost_d
Is that correct?


2. If I like the score to be independent of the number of terms in the
document (regarding them as essentially constant), is it enough to leave out
the norm_d_t factor?
I have seen that a norm factor between 0 and 255 is read with
IndexReader.norms() in TermScorer.score(). Is that the one?

>From what I further understand (and from digging in Witten/Moffat/Bell) the
norm_q factor is not calculated, since it stays the same for one query.

Just make some checkmarks, please :-)


Clemens






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