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From "Grant Ingersoll (JIRA)" <>
Subject [jira] Commented: (LUCENE-965) Implement a state-of-the-art retrieval function in Lucene
Date Thu, 26 Jul 2007 02:55:31 GMT


Grant Ingersoll commented on LUCENE-965:

What do people make of this?  Interesting claims.  I haven't looked at the patch yet or read
up on the Axiomatic retrieval model, but the precision numbers in the report are impressive.
 I think it dovetails nicely with Doron and Chris' discussions on retrieval performance and
making better efforts to gauge Lucene's retrieval effectiveness.  These numbers are for TREC
and that doesn't always correlate to the real world, but still, not to be discounted, either.

I think it would be cool to see a couple things out of this (at least):
1. contrib/benchmark algorithms to be applied for before and after, including LUCENE-836.
 This would give everyone a way of easily evaluating (assuming they have TREC data).  I would
wait for 836 to be committed, though, as it is not final yet.
2. Search speed numbers comparing the two approaches.  That is if it is significantly slower,
than it probably isn't going to be the default way of doing things

My gut reaction would be, if everything checks out of course, is to see how to factor it in
as a separate querying mechanism, if possible like the Spans functionality, to give people
the option of using this and if the claims hold up in the wild and feedback is positive, then
we could look to making it the default approach.  Not sure how feasible this is, though

In the meantime, looks like I've got some reading to do...


> Implement a state-of-the-art retrieval function in Lucene
> ---------------------------------------------------------
>                 Key: LUCENE-965
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Search
>    Affects Versions: 2.2
>            Reporter: Hui Fang
>         Attachments: axiomaticFunction.patch
> We implemented the axiomatic retrieval function, which is a state-of-the-art retrieval
function, to 
> replace the default similarity function in Lucene. We compared the performance of these
two functions and reported the results at

> The report shows that the performance of the axiomatic retrieval function is much better
than the default function. The axiomatic retrieval function is able to find more relevant
documents and users can see more relevant documents in the top-ranked documents. Incorporating
such a state-of-the-art retrieval function could improve the search performance of all the
applications which were built upon Lucene. 
> Most changes related to the implementation are made in AXSimilarity, TermScorer and
 However, many test cases are hand coded to test whether the implementation of the default
function is correct. Thus, I also made the modification to many test files to make the new
retrieval function pass those cases. In fact, we found that some old test cases are not reasonable.
For example, in the testQueries02 of, 
> the query is "+w3 xx", and we have two documents "w1 xx w2 yy w3" and "w1 w3 xx w2 yy
> The second document should be more relevant than the first one, because it has more 
> occurrences of the query term "w3". But the original test case would require us to rank

> the first document higher than the second one, which is not reasonable. 

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