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From Doug Cutting <cutt...@apache.org>
Subject Re: Search and Scoring
Date Wed, 13 Oct 2004 16:37:55 GMT
Chuck Williams wrote:
> I think there are at least two bugs here:
>   1.  idf should not be squared.

I discussed this in a separate message.  It's not a bug.

>   2.  explain() should explain the actual reported score().

This is mostly a documentation bug in Hits.  The normalization of scores 
to 1.0 is performed only by Hits.  Hits is a high-level wrapper on the 
lower-level HitCollector-based search implementations, which do not 
perform this normalization.  We should probably document that Hits 
scores are so normalized.  Also, we could add a method to disable this 
normalization in Hits.  The normalization was added long ago because 
many folks found it disconcerting when scores were greater than 1.0.

We should not attempt to normalize scores reported by explain().  The 
intended use of explain() is to compare its output against other calls 
to explain(), in order to understand how one document scores higher than 
another.  Scores don't make much sense in isolation, and neither do 
explanations.

Doug

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