Title: Contrastive Quantization based Semantic Code for Generative Recommendation

Abstract: With the success of large language models, generative retrieval has emerged as a new retrieval technique for recommendation. It can be divided into two stages: the first stage involves constructing discrete Codes (i.e., codes), and the second stage involves decoding the code sequentially via the transformer architecture. Current methods often construct item semantic codes by reconstructing based quantization on item textual representation, but they fail to capture item discrepancy that is essential in modeling item relationships in recommendation sytems. In this paper, we propose to construct the code representation of items by simultaneously considering both item relationships and semantic information. Specifically, we employ a pre-trained language model to extract item's textual description and translate it into item's embedding. Then we propose to enhance the encoder-decoder based RQVAE model with contrastive objectives to learn item code. To be specific, we employ the embeddings generated by the decoder from the samples themselves as positive instances and those from other samples as negative instances. Thus we effectively enhance the item discrepancy across all items, better preserving the item neighbourhood. Finally, we train and test semantic code with with generative retrieval on a sequential recommendation model. Our experiments demonstrate that our method improves NDCG@5 with 43.76% on the MIND dataset and Recall@10 with 80.95% on the Office dataset compared to the previous baselines.