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From Erik Hatcher <e...@ehatchersolutions.com>
Subject Re: search alogorithm in Lucene
Date Mon, 08 Aug 2005 18:13:44 GMT

On Aug 8, 2005, at 1:19 PM, Rajesh Munavalli wrote:
>> 2 How term weight is calculated in Lucene, how many types of term
>>
> weight calculating formulas are implemented and what are they?
> TF-IDF weighting is used with some modifications to how the raw  
> score is
> computed. You can refer to "Lucene In Action" by Otis Gospodnetic and
> Erik Hatcher" page 78. Here is the formula
>
> = SUMMATION  {tf(t in d).idf(t).boost(t.field in d). lengthNorm 
> (t.field
> in d)
>      t in q

Note that the most crucial errata for Lucene in Action is on that  
very formula.  The corrected one is here:

     http://www.lucenebook.com/blog/errata/scoring_formula_omission.html

Erik


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