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From Models to Systems: A Comprehensive Framework for AI System Fairness in Compositional Recommender Systems
Proceedings of the Algorithmic Fairness Through the Lens of Metrics and Evaluation, PMLR 279:8-37, 2025.
Abstract
Fairness research in machine learning often centers on ensuring equitable performance ofindividual models. However, real-world recommendation systems are built on multiplemodels and even multiple stages, from candidate retrieval to scoring and serving, whichraises challenges for responsible development and deployment. This AI system-level view,as highlighted by regulations like the EU AI Act, necessitates moving beyond auditingindividual models as independent entities. We propose a holistic framework for modelingAI system-level fairness, focusing on the end-utility delivered to diverse user groups, andconsider interactions between components such as retrieval and scoring models. We provideformal insights on the limitations of focusing solely on model-level fairness and highlight theneed for alternative tools that account for heterogeneity in user preferences. To mitigatesystem-level disparities, we adapt closed-box optimization tools (e.g., BayesOpt) to jointlyoptimize utility and equity. We empirically demonstrate the effectiveness of our proposedframework on synthetic and real datasets, underscoring the need for a framework thatreflects the design of modern, industrial AI systems.