CO*IR: A Greedy and Individually Fair Re-ranker

An open-source and greedy approach to individually fair re-ranking is presented, evaluated and tested. Previous literature on individually fair search suggested greedy-style heuristics, but no such designs or implementations were introduced before this writing. We release our re-ranker as a zero-dependency utility compatible with all major operating systems. We publish our re-ranker under a permissive software license (GPLv3). By explicitly considering individual fairness a post-processing (re-ranking) task, we implement the notion of individual fairness as a microservice, de-coupled from specific IR systems. Our software package works on commodity hardware, and finds application in small-to-medium-sized businesses, federated social networks, and under the broader open web search initiative.