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From Andrzej Bialecki ...@getopt.org>
Subject Re: Term weighting and Term boost
Date Fri, 16 Jan 2004 12:08:33 GMT
Karl Koch wrote:

>Hello all,
>
>I am new to the Lucene scene and have a few questions regarding the term
>boost physolophy:
>
>Is the term boost equal to a term weight? Example: If I boost a term with
>0.2 does this mean the term has a weight of 0.2 then?
>
>If this is not the case, how is the term weight of the query calculated
>then? Formula? Are there parts in it which I cannot influence? Does this formular
>depend on the type of Query or is it independent. Maybe somebody can provide
>a small code example? 
>  
>
I realize this is not exactly the answer, but you may want to try one of 
the new features of Luke (http://www.getopt.org/luke), namely the query 
result explanation.

Currently the best way to start Luke is to use Java WebStart. Then open 
an already existing index, go to the Search tab, enter a query (use 
"Update" button to see exactly what it is parsed into), press Search, 
and then highlight one of the results and press "Explain".

It was revealing for me to see how weights, boosts, normalizations etc. 
are applied "under the hood" so to speak, especially for  Fuzzy or 
Phrase queries.

After experimenting a little, you may want to consult the classes in 
org.apache.lucene.search (e.g. Scorer and Similarity) to see the gory 
details.

-- 
Best regards,
Andrzej Bialecki

-------------------------------------------------
Software Architect, System Integration Specialist
CEN/ISSS EC Workshop, ECIMF project chair
EU FP6 E-Commerce Expert/Evaluator
-------------------------------------------------
FreeBSD developer (http://www.freebsd.org)



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