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:
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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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