Evidence Conflict Sampling for Open-set Active Learning
摘要
Active learning (AL) in open-set scenarios introduces the challenge of handling unlabeled data containing significant noise from unknown classes. Traditional entropy-based AL methods fail to handle it because they cannot distinguish between informative examples and open-set noise. To address this, we propose Evidence COnflict (ECO) sampling, a novel query strategy to balance purity—prioritizing known classes and informativeness—maximizing learning utility. ECO leverages a naïve Bayes framework to quantify class-wise evidence and selects unlabeled examples based on two criteria: (1) sufficient evidence for known classes, ensuring query purity, and (2) conflicting evidence among classes, guaranteeing informativeness. This dual evidence-driven approach systematically filters out open-set noise while enhancing the discriminative power of the labeled dataset. We further establish a theoretical foundation for ECO, proving that the posterior variance of evidence distribution increases with a larger label space, ensuring its robustness in open-set scenarios. Extensive experiments on diverse benchmarks with varying openness ratios demonstrate the superiority of ECO over state-of-the-art methods in terms of both query efficiency and robustness to open-set noise.