The first term, known as the coverage, is the ratio between the size of the subgroup s(SG) and the size of the data set s( P). This term prevents the selection of too small SGs. The second term is the utility function u(SG, P) and provides a metric for the usefulness of the SGs. The target in our analysis is ∆d C-O max as defined in Eq. 2 and we aim at identifying rules describing structures with large ∆d C-O max values, Thus, we used the normalized positive mean shift function. This utility function favors SGs with high mean values of ∆d C-O max . Hence, we should identify SGs of SAA surface sites that can significantly activate CO 2 , and weaken at least one of its bonds.