It may not be easy or even possible without major changes, but having
global collection statistics would allow scores to be compared across
searchers. To do this, the master indexes would need to be able to
communicate with each other.
An other approach to merging across searchers is described here:
Steven M. Beitzel, Eric C. Jensen, Abdur Chowdhury, Greg Pass, Ophir
Frieder,
"Surrogate Scoring for Improved Metasearch Precision" , Proceedings
of the 2005 ACM Conference on Research and Development in Information
Retrieval (SIGIR-2005), Salvador, Brazil, August 2005.
-Sean
[EMAIL PROTECTED] wrote:
On 4/11/07, Chris Hostetter
<[EMAIL PROTECTED]> wrote:
A custom Similaity class with simplified tf, idf, and queryNorm
functions
might also help you get scores from the Explain method that are more
easily manageable since you'll have predictible query structures hard
coded into your application.
ie: run the large query once, get the results back, and for each result
look at the explanation and pull out the individual pieces of hte
explanation and compare them with those of hte other matches to create
your own "normalization".
Chuck Williams mentioned a proposal he had for normalization of scores
that
would give a constant score range that would allow comparison of
scores.
Chuck, did you ever write any code to that end or was it just
algorithmic
discussion?
Here is the point I'm at now:
I have my matching engine working. The fields to be indexed and the
queries
are defined by the user. Hoss, I'm not sure how that affects your idea
of
having a custom Similarity class since you mentioned that having
predictable
query structures was important...
The user kicks off an indexing then defines the queries they want to
try
matching with. Here is an example of the query fragments I'm working
with
right now:
year_str:"${Year}"^2 year_str:[${Year -1} TO ${Year +1}]
title_title_mv:"${Title}"^10 title_title_mv:${Title}^2
+(title_title_mv:"${Title}"~^5 title_title_mv:${Title}~)
director_name_mv:"${Director}"~2^10 director_name_mv:${Director}^5
director_name_mv:${Director}~.7
For each item in the source feed, the variables are interpolated (the
query
term is transformed into a grouped term if there are multiple values
for a
variable). That query is then made to find the overall best match.
I then determine the relevance for each query fragment. I haven't
written
any plugins for Lucene yet, so my current method of determining the
relevance is by running each query fragment by itself then iterating
through
the results looking to see if the overall best match is in this result
set.
If it is, I record the rank and multiply that rank (e.g. 5 out of 10)
by a
configured fragment weight.
Since the scores aren't normalized, I have no good way of determining a
poor
overall match from a really high quality one. The overall item could be
the
first item returned in each of the query fragments.
Any help here would be very appreciated. Ideally, I'm hoping that maybe
Chuck has a patch or plugin that I could use to normalize my scores
such
that I could let the user do a matching run, look at the results and
determine what score threshold to set for subsequent runs.
Thanks,
Daniel
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