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From Doug Cutting <cutt...@lucene.com>
Subject Re: Are score values always between 0 and 1?
Date Wed, 16 Oct 2002 18:09:19 GMT
Dmitry Serebrennikov wrote:
> I know that the FAQ says that they are, but in at least one instance in 
> my index it appears to be equal to 1.94something. Are the scores 
> guaranteed to be between 0 and 1

No.

 > and if not, what would it take to make
> them such?

A different Similarity implementation.

To do this right you need to divide each document's score by the square 
root of the sum of all of the document's term weights.  This is hard to 
do, since the term weights depend on each term's document frequency and 
hence change when documents are added and deleted from the index.  Thus 
this denominator would have to be recomputed for every document each 
time the index changes.  Or you could use term weights that don't depend 
on document frequency, or ...

Doug


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