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From Grant Ingersoll <gsing...@apache.org>
Subject Re: [jira] Commented: (LUCENE-954) Toggle score normalization in Hits
Date Fri, 22 Feb 2008 12:57:43 GMT

On Feb 22, 2008, at 7:10 AM, Christian Kohlschütter (JIRA) wrote:

>
>    [ https://issues.apache.org/jira/browse/LUCENE-954?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12571367

> #action_12571367 ]
>
> Christian Kohlschütter commented on LUCENE-954:
> -----------------------------------------------
>
> Grant,
>
> sorry I was perhaps not too clear about it.
>
> The distribution of scores of one Hits instance is currently not  
> comparable to another distribution of scores of another Hits object,  
> even if the underlying statistics are comparable/compatible/ 
> identical. This is due to the case that the values are always  
> normalized to a maximum of 1.0.
>
> As I said, my Federated Search system provides homogeneous  
> statistics (but not via MultiSearcher). In fact, it does not use  
> MultiSearcher for this, but a variant of the SRU/SRW/XCQL protocols  
> ("SRX/FS"), where all communication is done via HTTP and XML. This  
> includes the exchange of Term/DF statistics. At the end, the system  
> makes several distributed Indexes appear as a single (read:  
> federated) index. In order to merge the results from each index,  
> Hits is used.

Gotcha.  It wasn't clear that you were exchanging the searchers were  
aware of global statistics.  I think the use of "federated" is what  
through me off.  I have understood your description to be better  
called "distributed search", whereas federated search is more along  
the lines of disparate indexes that don't share statistics.  I know,  
"you say tomato,..."

In the distributed case, yes, it does make sense to be able to compare  
the scores.
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