“…To address the sparsity problem of user-app interactions, researchers usually turn to feature-rich scenarios, where side information of users and apps is used to compensate for the sparsity and improve the performance of recommendation. As detailed in section 5, most of them [2,3,4,5,6,7,8,9,10] only exploited limited types of side information. In addition, they usually treated different kinds of side information as isolated features of users and apps, and neglected the relations and semantics of them.…”