CTRec: A Long Short Demands Evolution Model for Continuous Time Recommendation
In e commerce, users' demands are not only conditioned by their profile and preferences, but also by their recent purchases that may generate new demands, as well as periodical demands that depend on purchases made some time ago. We call them respectively short term demands and long term demands. In this paper, we propose a novel self attentive Continuous Time Recommendation model (CTRec) for capturing the evolving demands of users over time. For modeling such time sensitive demands, a Demand aware Hawkes Process (DHP) framework is designed in CTRec to learn from the discrete purchase records of users. More specifically, a convolutional neural network is utilized to capture the short term demands; and a self attention mechanism is employed to capture the periodical purchase cycles of long term demands. All types of demands are fused in DHP to make final continuous time recommendations. We conduct extensive experiments on four real world commercial datasets to demonstrate that CTRec is effective for general sequential recommendation problems, including next item and next session/basket recommendations. We observe in particular that CTRec is capable of learning the purchase cycles of products and estimating the purchase time of a product given a user.
SIGIR