  As Federated Learning (FL) has gained increasing attention, it has become
widely acknowledged that straightforwardly applying stochastic gradient descent
(SGD) on the overall framework when learning over a sequence of tasks results
in the phenomenon known as ``catastrophic forgetting''. Consequently, much FL
research has centered on devising federated increasing learning methods to
alleviate forgetting while augmenting knowledge. On the other hand, forgetting
is not always detrimental. The selective amnesia, also known as federated
unlearning, which entails the elimination of specific knowledge, can address
privacy concerns and create additional ``space'' for acquiring new knowledge.
However, there is a scarcity of extensive surveys that encompass recent
advancements and provide a thorough examination of this issue. In this
manuscript, we present an extensive survey on the topic of knowledge editing
(augmentation/removal) in Federated Learning, with the goal of summarizing the
state-of-the-art research and expanding the perspective for various domains.
Initially, we introduce an integrated paradigm, referred to as Federated
Editable Learning (FEL), by reevaluating the entire lifecycle of FL. Secondly,
we provide a comprehensive overview of existing methods, evaluate their
position within the proposed paradigm, and emphasize the current challenges
they face. Lastly, we explore potential avenues for future research and
identify unresolved issues.
