  The recent advent of self-supervised pre-training techniques has led to a
surge in the use of multimodal learning in form document understanding.
However, existing approaches that extend the mask language modeling to other
modalities require careful multi-task tuning, complex reconstruction target
designs, or additional pre-training data. In FormNetV2, we introduce a
centralized multimodal graph contrastive learning strategy to unify
self-supervised pre-training for all modalities in one loss. The graph
contrastive objective maximizes the agreement of multimodal representations,
providing a natural interplay for all modalities without special customization.
In addition, we extract image features within the bounding box that joins a
pair of tokens connected by a graph edge, capturing more targeted visual cues
without loading a sophisticated and separately pre-trained image embedder.
FormNetV2 establishes new state-of-the-art performance on FUNSD, CORD, SROIE
and Payment benchmarks with a more compact model size.
