A Survey on Operational Transformation Algorithms: Challenges, Issues and Achievements 1 <s> OPERATIONAL TRANSFORMATION <s> Groupware systems are computer-based systems that support two or more users engaged in a common task, and that provide an interface to a shared environment. These systems frequently require fine-granularity sharing of data and fast response times. This paper distinguishes real-time groupware systems from other multi-user systems and discusses their concurrency control requirements. An algorithm for concurrency control in real-time groupware systems is then presented. The advantages of this algorithm are its simplicity of use and its responsiveness: users can operate directly on the data without obtaining locks. The algorithm must know some semantics of the operations. However the algorithm's overall structure is independent of the semantic information, allowing the algorithm to be adapted to many situations. An example application of the algorithm to group text editing is given, along with a sketch of its proof of correctness in this particular case. We note that the behavior desired in many of these systems is non-serializable. <s> BIB001 </s> A Survey on Operational Transformation Algorithms: Challenges, Issues and Achievements 1 <s> OPERATIONAL TRANSFORMATION <s> Rd-time group editors dow a group of users to view and edit, the same document at the same time horn geograpbicdy di.~ersed sites connected by communication networks. Consistency maintenance is one of the most si@cant &alwiges in the design and implementation of thwe types of systems. R=earch on rd-time group editors in the past decade has invented au inuolative tetique for consistency maintenance, ded operational transformation This paper presents an integrative review of the evolution of operational tra=formation techniques, with the go~ of identifying the major is-m~s, dgotiths, achievements, and remaining Mlenges. In addition, this paper contribut= a new optimized generic operational transformation control algorithm. Ke~vords Consistency maint enauce, operational transformation, convergence, CauS*ty pras~ation, intention pre~tion, group e&tors, groupware, distributed computing. <s> BIB002
OT BIB001 BIB002 is an optimistic consistency control method that lies in the heart of many collaborative applications such as group editors and Google Wave1. The method replicates the shared data at cooperating sites. Local operations are always executed as soon as they are generated by the user. Remote operations are transformed before execution to repair inconsistencies.