Table 2. Summary of the big data analytics in unsupervised learning mechanisms.

Paper	AI technique	Scalability	Efficiency	Precision	Privacy
Ianni et al. (2020)	Centroid-based clustering	√	√	√	X
Wang, Tsai & Ciou (2020)	RFM, K-means, Naïve Bayes, Bloom filters	X	√	√	X
Ip et al. (2018)	Markov random fields	√	X	√	X
Pulgar-Rubio et al. (2017)	Multi-objective evolutionary fuzzy systems	√	√	√	X