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Summary: A Unified Model for Metasearch and the Efficient
Evaluation of Retrieval Systems via the Hedge Algorithm
Javed A. Aslam, Virgiliu Pavlu, Robert Savell
Department of Computer Science
Dartmouth College
{jaa,virgilpavlu,rsavell}@cs.dartmouth.edu
ABSTRACT
We present a unified framework for simultaneously solving
both the pooling problem (the construction of efficient doc-
ument pools for the evaluation of retrieval systems) and
metasearch (the fusion of ranked lists returned by retrieval
systems in order to increase performance). The implemen-
tation is based on the Hedge algorithm for online learning,
which has the advantage of convergence to bounded error
rates approaching the performance of the best linear com-
bination of the underlying systems. The choice of a loss
function closely related to the average precision measure of
system performance ensures that the judged document set
performs well, both in constructing a metasearch list and
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