Table 2.

Comparison of AI techniques used by travel recommender systems.

Articles	Multiagent system	Optimization technique	Automatic clustering	Management of uncertainty	Knowledge representation
García-Manotas et al. [84]		✓
Sebastia et al. [63]	✓				✓
Vansteenwegen et al. [44]		✓
Fenza et al. [85]			✓
Garcia et al. [65]					✓
Gavalas and Kenteris [51]			✓
Lorenzi et al. [59]	✓
Wang et al. [49]				✓	✓
Batet et al. [67]			✓		✓
Hsu et al. [86]				✓
Martínez-Santiago et al. [53]					✓
Noguera et al. [58]			✓
Garcia et al. [69]		✓
Lucas et al. [72]			✓	✓	✓
Meehan et al. [73]		✓		✓
Moreno et al. [87]			✓		✓
Ruotsalo et al. [74]			✓	✓	✓