  Domain Generalization (DG) is a fundamental challenge for machine learning
models, which aims to improve model generalization on various domains. Previous
methods focus on generating domain invariant features from various source
domains. However, we argue that the domain variantions also contain useful
information, ie, classification-aware information, for downstream tasks, which
has been largely ignored. Different from learning domain invariant features
from source domains, we decouple the input images into Domain Expert Features
and noise. The proposed domain expert features lie in a learned latent space
where the images in each domain can be classified independently, enabling the
implicit use of classification-aware domain variations. Based on the analysis,
we proposed a novel paradigm called Domain Disentanglement Network (DDN) to
disentangle the domain expert features from the source domain images and
aggregate the source domain expert features for representing the target test
domain. We also propound a new contrastive learning method to guide the domain
expert features to form a more balanced and separable feature space.
Experiments on the widely-used benchmarks of PACS, VLCS, OfficeHome, DomainNet,
and TerraIncognita demonstrate the competitive performance of our method
compared to the recently proposed alternatives.
