Operational transformation in cooperative software systems

Modern cooperative software systems involve multiple concurrent users undertaking a common task in a real-time distributed environment, such as editing a shared text document. Maintaining data consistency, transaction causality, and replication convergence in such an environment, while providing fast client responsiveness, is a substantial challenge for classical distributed computing techniques. Operational transformation (OT) is a class of concurrency algorithms and data models that supports these functionalities, which has drawn significant research attention in the past decade. In this review, we discuss the basic components of operational transformation models, the algorithms involved, and their actual implementations in real-world networked systems. We compare several existing OT control algorithms, the transformation functions and properties supported by each of the algorithms, and the trade-offs that are made with respect to each one. The data and operational models used in OT are well suited for high- latency environments such as the Internet, making them more frequently used in modern web services. Although many different OT control algorithms exist, choosing the most effective one often depends on the particular operations that an application must support.