A semi-transparent selective undo algorithm for multi-user collaborative editors

Multi-user collaborative editors are useful computer-aided tools to support human-to-human collaboration.For multi-user collaborative editors,selective undo is an essential utility enabling users to undo any editing operations at any time.Collaborative editors usually adopt operational transformation(OT)to address concurrency and consistency issues.However,it is still a great challenge to design an efficient and correct OT algorithm capable of handling both normal do operations and user-initiated undo operations because these two kinds of operations can interfere with each other in various forms.In this paper,we propose a semi-transparent selective undo algorithm that handles both do and undo in a unified framework,which separates the processing part of do operations from the processing part of undo operations.Formal proofs are provided to prove the proposed algorithm under the well-established criteria.Theoretical analysis and experimental evaluation are conducted to show that the proposed algorithm outperforms the prior OT-based selective undo algorithms.