  Active Domain Adaptation (ADA) aims to maximally boost model adaptation in a
new target domain by actively selecting a limited number of target data to
annotate.This setting neglects the more practical scenario where training data
are collected from multiple sources. This motivates us to target a new and
challenging setting of knowledge transfer that extends ADA from a single source
domain to multiple source domains, termed Multi-source Active Domain Adaptation
(MADA). Not surprisingly, we find that most traditional ADA methods cannot work
directly in such a setting, mainly due to the excessive domain gap introduced
by all the source domains and thus their uncertainty-aware sample selection can
easily become miscalibrated under the multi-domain shifts. Considering this, we
propose a Dynamic integrated uncertainty valuation framework(Detective) that
comprehensively consider the domain shift between multi-source domains and
target domain to detect the informative target samples. Specifically, the
leverages a dynamic Domain Adaptation(DA) model that learns how to adapt the
model's parameters to fit the union of multi-source domains. This enables an
approximate single-source domain modeling by the dynamic model. We then
comprehensively measure both domain uncertainty and predictive uncertainty in
the target domain to detect informative target samples using evidential deep
learning, thereby mitigating uncertainty miscalibration. Furthermore, we
introduce a contextual diversity-aware calculator to enhance the diversity of
the selected samples. Experiments demonstrate that our solution outperforms
existing methods by a considerable margin on three domain adaptation
benchmarks.
