Order Matters: Alibaba's Transformer-based Recommender System

Alibaba, the largest e-commerce platform in China, is a powerhouse not only when it comes to e-commerce, but also when it comes to recommender systems research. Their latest paper, Behaviour Sequence Transformer for E-commerce Recommendation in Alibaba, is yet another publication that pushes the state of the art in recommender systems. In this work, they make use of the popular Transformer model to capture sequential signals in user behaviour in online shopping, in order to perform next click prediction. Recommender systems often make use of a 2-stage paradigm of retrieval and ranking, and Alibaba's approach is no different. The retrieval step used at Alibaba consists of selecting, with high recall, a subset of a million relevant candidate items from the entire item set (which is of course much larger than a million possible items), and the ranking step consists of ranking these candidates with high precision.