Taobao Search consists of two phases: the retrieval phase and the ranking phase. Given a user query, the retrieval phase returns a subset of candidate products for the following ranking phase. Recently, the paradigm of pre-training and fine-tuning has shown its potential in incorporating visual clues into retrieval tasks. In this paper, we focus on solving the problem of text-to-multimodal retrieval in Taobao Search. We consider that users' attention on titles or images varies on products. Hence, we propose a novel Modal Adaptation module for cross-modal fusion, which helps assigns appropriate weights on texts and images across products. Furthermore, in e-commerce search, user queries tend to be brief and thus lead to significant semantic imbalance between user queries and product titles. Therefore, we design a separate text encoder and a Keyword Enhancement mechanism to enrich the query representations and improve text-to-multimodal matching. To this end, we present a novel vision-language (V+L) pre-training methods to exploit the multimodal information of (user query, product title, product image). Extensive experiments demonstrate that our retrieval-specific pre-training model (referred to as MAKE) outperforms existing V+L pre-training methods on the text-to-multimodal retrieval task. MAKE has been deployed online and brings major improvements on the retrieval system of Taobao Search.

翻译：淘宝搜索包含两个阶段：检索阶段和排序阶段。给定用户查询，检索阶段为后续排序阶段返回候选商品子集。近年来，预训练-微调范式在将视觉线索融入检索任务中展现出潜力。本文聚焦于解决淘宝搜索中的文本到多模态检索问题。我们注意到用户对商品标题或图像的关注度存在差异，因此提出新颖的模态自适应模块用于跨模态融合，该模块能跨商品为文本和图像分配适当权重。此外，电子商务搜索中的用户查询往往简短，导致用户查询与商品标题之间存在显著语义不平衡。为此，我们设计独立的文本编码器和关键词增强机制来丰富查询表示，并提升文本到多模态的匹配效果。基于此，我们提出新的视觉-语言（V+L）预训练方法以挖掘（用户查询、商品标题、商品图像）的多模态信息。大量实验表明，我们专为检索设计的预训练模型（简称MAKE）在文本到多模态检索任务上优于现有V+L预训练方法。MAKE已在线部署，为淘宝搜索检索系统带来了显著改进。