A Survey on Continual Semantic Segmentation: Theory, Challenge, Method
  and Application
Bo Yuan Danpei Zhao
Continual learning, also known as incremental learning or life-long learning,
stands at the forefront of deep learning and AI systems. It breaks through the
obstacle of one-way training on close sets and enables continuous adaptive
learning on open-set conditions. In the recent decade, continual learning has
been explored and applied in multiple fields especially in computer vision
covering classification, detection and segmentation tasks. Continual semantic
segmentation (CSS), of which the dense prediction peculiarity makes it a
challenging, intricate and burgeoning task. In this paper, we present a review
of CSS, committing to building a comprehensive survey on problem formulations,
primary challenges, universal datasets, neoteric theories and multifarious
applications. Concretely, we begin by elucidating the problem definitions and
primary challenges. Based on an in-depth investigation of relevant approaches,
we sort out and categorize current CSS models into two main branches including
\textit{data-replay} and \textit{data-free} sets. In each branch, the
corresponding approaches are similarity-based clustered and thoroughly
analyzed, following qualitative comparison and quantitative reproductions on
relevant datasets. Besides, we also introduce four CSS specialities with
diverse application scenarios and development tendencies. Furthermore, we
develop a benchmark for CSS encompassing representative references, evaluation
results and reproductions, which is available
at~\url{https://github.com/YBIO/SurveyCSS}. We hope this survey can serve as a
reference-worthy and stimulating contribution to the advancement of the
life-long learning field, while also providing valuable perspectives for
related fields.