Negative Semantic Guided Identity Boundary Construction for Open-World Person Re-Identification

Person re-identification (ReID) aims to match person images of the same identity under different camera views. Conventional ReID models mainly consider a closed-world setting where person identities in query and gallery are exactly the same. However, in real-world applications, query identities and gallery identities usually do not exactly contain the same persons. Therefore, open-world ReID has been proposed to match the images of gallery identities (targets) with a large number of non-gallery identities ( non-targets). Since some non-targets are quite similar to the targets, the ReID model may make incorrect judgments when verifying these non-targets. To solve this problem, we leverage the impressive cross-modal matching capabilities of the large vision-language model (VLM) to construct Negative Semantic guided identity boundaries for each person to develop the open-world ReID model (NS-ReID). To construct the identity boundary, we propose Virtual Non-target Repulsion that utilizes negative semantics to prompt the ReID model to push virtual non-targets away from the targets. The prompts expressing negative semantics offer a different perspective to guide the training process to avoid contradictory optimization. Moreover, we propose the Dual-Boost Refinement Learning strategy to train learnable identity prompts to capture detailed identity information, which is essential for constructing the identity boundary since the variations among identities are comparatively small. These facilitate the model in constructing the wide identity boundary of each person. Extensive experiments on two benchmark ReID datasets demonstrate that our proposed NS-ReID achieves state-of-the-art performance compared with existing methods.