  Supervised neural approaches are hindered by their dependence on large,
meticulously annotated datasets, a requirement that is particularly cumbersome
for sequential tasks. The quality of annotations tends to deteriorate with the
transition from expert-based to crowd-sourced labelling. To address these
challenges, we present \textbf{CAMELL} (Confidence-based Acquisition Model for
Efficient self-supervised active Learning with Label validation), a pool-based
active learning framework tailored for sequential multi-output problems. CAMELL
possesses three core features: (1) it requires expert annotators to label only
a fraction of a chosen sequence, (2) it facilitates self-supervision for the
remainder of the sequence, and (3) it employs a label validation mechanism to
prevent erroneous labels from contaminating the dataset and harming model
performance. We evaluate CAMELL on sequential tasks, with a special emphasis on
dialogue belief tracking, a task plagued by the constraints of limited and
noisy datasets. Our experiments demonstrate that CAMELL outperforms the
baselines in terms of efficiency. Furthermore, the data corrections suggested
by our method contribute to an overall improvement in the quality of the
resulting datasets.
