Conditions and Patterns for Achieving Convergence in OT-Based Co-Editors

Xu, Yi; Sun, Changyin

doi:10.1109/tpds.2015.2412938

Cited by 21 publications

(24 citation statements)

References 23 publications

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“…Though this theoretic complexity was not a concern in real-time co-editors because typically c ≤ 10 [61], more efficient control algorithms were proposed (e.g. Jupiter [36], NICE [49], TIBOT [26,84], SOCT4 [77], Google Wave and Docs OT [11,34,78], COT [66,67], and POT [84]), with a time complexity of O(c) for transforming a remote operation. For processing local operations, OT solutions generally have the constant time complexity O(1) 6 .…”

Section: Control Algorithms and The Dopt Puzzlementioning

confidence: 99%

“…It is worth highlighting that the transformation function T, document state DS, and operation O are all unspecified in CP1 and CP2 specifications, meaning CP1 and CP2 are applicable to transformation functions defined for any document states and operation models. Establishing general transformation conditions and properties for correctness, including CP1 and CP2, is one of major achievements in past OT research [13,38,43,54,55,61,66,67,70,71,84].…”

Section: Transformation Functions and The False-tie Puzzlementioning

confidence: 99%

“…One fundamental point we should highlight at the start is that CP2 is not unconditionally required, but required for transformation functions only if the control algorithms in the OT solution transform concurrent operations in arbitrary orders, or more precisely, transform the same pair of concurrent operations in different contexts [43,61,66,67,84]. This CP2 precondition has played a key role in the invention and verification of OT solutions to the CP2 issue along two alternative paths.…”

Section: Solving the Cp2 Issue And The Ft Puzzle Under The Ot Approachmentioning

confidence: 99%

“…The correctness of key OT components, including generic control algorithms and transformation functions for a range of commonly used operation and data models (e.g. string-wise plain-text editing and beyond) [1,3,69,70,71], has been established under well-defined conditions and properties [13,31,38,43,54,55,58,61,67,71,84]…”

Section: Summary Of Correctness and Complexity Of Ot Solutionsmentioning

confidence: 99%

“…CP1 and CP2 are unnecessary for transformation functions because they can be avoided by using OT control algorithms (e.g. CP2avoidance algorithms [11,26,34,36,49,50,67,77,78,84]). CP1 and CP2 are insufficient because they govern only convergence, but not intention preservation (e.g.…”

Section: Are Cp1 and Cp2 Necessary And Sufficient Conditions For Ot Cmentioning

confidence: 99%

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Real Differences between OT and CRDT under a General Transformation Framework for Consistency Maintenance in Co-Editors

Sun

Sun²,

et al. 2020

Proc. ACM Hum.-Comput. Interact.

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OT (Operational Transformation) was invented for supporting real-time co-editors in the late 1980s and has evolved to become a core technique used in today's working co-editors and adopted in major industrial products. CRDT (Commutative Replicated Data Type) for co-editors was first proposed around 2006, under the name of WOOT (WithOut Operational Transformation). Follow-up CRDT variations are commonly labeled as "post-OT" techniques and have made broad claims of superiority over OT solutions, in terms of correctness, time and space complexity, simplicity, etc. Over one decade later, however, OT remains the choice for building the vast majority of co-editors, whereas CRDT is rarely found in working co-editors. Why? Based on comprehensive review and comparison on representative OT and CRDT solutions and co-editors based on them, we present our discoveries in relation to this question and beyond in a series of three articles.In prior work, we have revealed that CRDT is like OT in following the same general transformation approach and CRDT is not natively commutative for concurrent operations in co-editors, which helps to clarify what CRDT really is and is not for co-editors. In this article, we reveal OT and CRDT differences in correctness and complexity by dissecting and examining representative OT and CRDT solutions. We explore how different basic approaches ̶ the concurrency-centric approach taken by OT and the content-centric approach taken by CRDT ̶ had resulted in different technical challenges, correctness and complexity issues, and solutions. Moreover, we reveal hidden algorithmic flaws with representative CRDT solutions, and discuss common myths and facts related to correctness, time and space complexity, and simplicity of OT and CRDT. We present facts and evidences that refute CRDT claimed advantages over OT. We hope the discoveries from this work help clear up common myths and confusions surrounding OT and CRDT, and accelerate progress in co-editing technology for real world applications. ; URL: https://www.ntu.edu.sg/home/CZSun 20,38,43,54,55,58,61,70,71,77], and support real-time collaboration in rich-text co-editing in word processors [60,65,68,82], HTML/XML Web document co-editing [10], spreadsheet co-editing [69], 3D model co-editing in digital media design tools [1,2], and file synchronization in cloud storage systems [3]. Recent years have seen OT being widely adopted in industry products as the core technique for consistency maintenance, ranging from battle-tested online collaborative richtext editors like Google Docs 1 [11], to emerging start-up products, such as Codox Apps 2 .A variety of alternative techniques for consistency maintenance in co-editors had also been explored in the past decades [14,16,18,41,42,72]. One notable class of techniques is CRDT 3 (Commutative Replicated Data Type) for co-editors [4,5,8,25,32,37,39,40,41,45,47,48,79,80,81]. The first CRDT solution for plain-text co-editing appeared around 2006 [40,41], under the name of WOOT (WithOut Operational Transformation). One mo...

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Section: Control Algorithms and The Dopt Puzzlementioning

confidence: 99%

Section: Transformation Functions and The False-tie Puzzlementioning

confidence: 99%

Section: Solving the Cp2 Issue And The Ft Puzzle Under The Ot Approachmentioning

confidence: 99%

Section: Summary Of Correctness and Complexity Of Ot Solutionsmentioning

confidence: 99%

Section: Are Cp1 and Cp2 Necessary And Sufficient Conditions For Ot Cmentioning

confidence: 99%

See 3 more Smart Citations

Real Differences between OT and CRDT under a General Transformation Framework for Consistency Maintenance in Co-Editors

Sun

Sun²,

et al. 2020

Proc. ACM Hum.-Comput. Interact.

Self Cite

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Self‐compressing object sequence for consistency maintenance in co‐editors

Cai

Yang

et al. 2022

Softw Pract Exp

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Co-editors are a class of human-centered collaborative systems that allow multiple geographically dispersed people to freely and concurrently edit shared documents at the same time over networks. The most important building co-editors technique is consistency maintenance. Even though OT (operational transformation) is a widely adopted consistency maintenance technique, researchers and practitioners have persistently explored alternative techniques to OT. One of the representative techniques is AST (Address Space Transformation), which replaces OT's transformation components with basic manipulation on an additional object sequence. However, the additional object sequence causes an unbounded metadata overhead problem. To solve the problem, this work proposes an optimized AST algorithm called ASTO, which is equipped with a specially designed self-compressing object sequence. ASTO can automatically compress the object sequence and keep the metadata overhead under control.The effectiveness and feasibility of ASTO are verified by simulation experiments and a publicly accessible prototype system.

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Supporting Cross-Platform Real-Time Collaborative Programming: Architecture, Techniques, and Prototype System

Yang

Chiu

et al. 2021

Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering

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Conditions and Patterns for Achieving Convergence in OT-Based Co-Editors

Cited by 21 publications

References 23 publications

Real Differences between OT and CRDT under a General Transformation Framework for Consistency Maintenance in Co-Editors

Real Differences between OT and CRDT under a General Transformation Framework for Consistency Maintenance in Co-Editors

Self‐compressing object sequence for consistency maintenance in co‐editors

Supporting Cross-Platform Real-Time Collaborative Programming: Architecture, Techniques, and Prototype System

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