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IRX is a text retrieval system designed to be a testbed for conducting information retrieval research on statistically-based retrieval strategies in either batch or interactive modes. The modular structure of IRX has permitted major changes in components of the system (e.g., ranking algorithms, parsers, interfaces; without redesign. As an interactive system IRX is in use at the Johns Hopkins University and the Lister Hill Center providing access to databases in human and molecular genetics.
Harman et al. (Sun,) studied this question.