  Scene Graph Generation (SGG) plays a pivotal role in downstream
vision-language tasks. Existing SGG methods typically suffer from poor
compositional generalizations on unseen triplets. They are generally trained on
incompletely annotated scene graphs that contain dominant triplets and tend to
bias toward these seen triplets during inference. To address this issue, we
propose a Triplet Calibration and Reduction (T-CAR) framework in this paper. In
our framework, a triplet calibration loss is first presented to regularize the
representations of diverse triplets and to simultaneously excavate the unseen
triplets in incompletely annotated training scene graphs. Moreover, the unseen
space of scene graphs is usually several times larger than the seen space since
it contains a huge number of unrealistic compositions. Thus, we propose an
unseen space reduction loss to shift the attention of excavation to reasonable
unseen compositions to facilitate the model training. Finally, we propose a
contextual encoder to improve the compositional generalizations of unseen
triplets by explicitly modeling the relative spatial relations between subjects
and objects. Extensive experiments show that our approach achieves consistent
improvements for zero-shot SGG over state-of-the-art methods. The code is
available at https://github.com/jkli1998/T-CAR.
