  Multi-Objective Recommender Systems (MORSs) emerged as a paradigm to
guarantee multiple (often conflicting) goals. Besides accuracy, a MORS can
operate at the global level, where additional beyond-accuracy goals are met for
the system as a whole, or at the individual level, meaning that the
recommendations are tailored to the needs of each user. The state-of-the-art
MORSs either operate at the global or individual level, without assuming the
co-existence of the two perspectives. In this study, we show that when global
and individual objectives co-exist, MORSs are not able to meet both types of
goals. To overcome this issue, we present an approach that regulates the
recommendation lists so as to guarantee both global and individual
perspectives, while preserving its effectiveness. Specifically, as individual
perspective, we tackle genre calibration and, as global perspective, provider
fairness. We validate our approach on two real-world datasets, publicly
released with this paper.
