“…Half of the works presented in [28] implement hybrid systems. Several recommendation systems integrate artificial intelligence techniques such as multi-agent systems [30][31][32], optimisation techniques (ant colony optimisation [33], genetic algorithms [34], iterated local search [2,35], greedy randomised adaptive search methods [36]), automatic clustering (k-nearest neighbours approach [37,38], k-means algorithms [39,40], fuzzy c-means [41]), management of uncertainty (Bayesian networks, fuzzy logic [42,43], rule-based approaches [44], and knowledge representation (ontologies [45][46][47]). For the evaluation of these systems, four methods are proposed in [29]: (1) real-life evaluations (based on precision, recall, and the harmonic mean of both precision and recall), (2) heuristic-based evaluations (based on total POI recommended, POI popularity or tourist interest), (3) crowd-based evaluations (using qualitative measures that focus on user experiences), and (4) online controlled experiments (design-based variants and algorithm-based variants).…”