24.5.2.1 Related work: multi-criteria optimization
Multi-criteria optimization problems have been extensively studied in the operations
research (OR) literature [21], although not in the context of recommender systems.
This multi-criteria optimization approach assists a decision maker in choosing the
best alternative when multiple criteria conflict and compete with each other. For
example, various points of view, such as financial, human resources-related, and
environmental aspects should be considered in organizational decision making. The
following approaches are often used to address multi-criteria optimization problems,
and can be applied to recommender systems, as discussed in [4]:
• Finding Pareto optimal solutions;
• Taking a linear combination of multiple criteria and reducing the problem to the
single-criterion optimization problem;
• Optimizing only the most important criterion and converting other criteria to
constraints;
• Consecutively optimizing one criterion at a time, converting an optimal solution
to constraints and repeating the process for other criteria.
Below we describe several recommendation approaches that have been used in
the recommender systems literature, all of them having roots in multi-criteria optimization techniques.