24.5.2.3 Finding Pareto optimal item recommendations
This approach discovers several good items among large number of candidates
(rather than arriving at a unique solution by solving a global optimization problem) when different items can be associated with multiple conflicting criteria and
the total order on items is not directly available. Data envelopment analysis (DEA),
often also called “frontier analysis”, is commonly used to measure productive efficiency of decision making units (DMU) in operations research [13]. DEA computes
the efficiency frontier, which identifies the items that are “best performers” overall, taking into account all criteria. DEA does not require a priori weights for each
criterion, and uses linear programming to arrive more directly at the best set of
weights for each DMU. Specifically, in the context of multi-criteria recommender
systems, given all the candidate items that are available for recommendation to a
given user (including the information about their predicted ratings across all criteria), DEA would be able to determine the reduced set of items (i.e., the frontier) that
have best ratings across all criteria among the candidates. These items then can be
recommended to the user.
While DEA has not been directly used in multi-criteria rating recommenders, the
multi-criteria recommendation problem without overall ratings can also be formulated as a data query problem in the database field, using similar motivation [43].
Lee and Teng [43] utilize skyline queries to find the best restaurants across multiple criteria (i.e., food, d´ecor, service, and cost). As Fig. 24.3 shows, skyline queries