“…Specifically, given the label space Y, label ranking aims to assign each instance x with the correct ranking of all the labels, that is, a complete/partial, transitive, and asymmetric relation x defined on Y, where i x j means that the label i precedes the label j in the ranking associated with x. According to the taxonomy established by [26], label ranking methods can be divided into four categories: the ones decomposing the original problem to multiple simple objectives such as pointwise function [27], [28] and pairwise ranking loss [29], [30]; probabilistic methods including tree-based model [31], [32], [33], [34], [35], Gaussian mixture model [36] and structured learning [37]; the ones based on similarity [38], [39], [40]; and the rule-based ones [41], [42]. Please refer to the surveys for more details [26], [43].…”