1. INTRODUCTION
Recommendation system has become essential to alleviate the problem of information explosion and considerable research efforts are devoted to enhance the recommendation performance, ranging from collaborative filtering [1], latent factor model [2], [3] to deep neural network [4], [5] and graph neural network [6], [7], [8], etc. However, recommender system still remains a black-box. To increase its persuasiveness, explainable recommendation is an emerging topic which sheds light on the uncertainties with convincing explanation.