A sequence transformation algorithm for supporting cooperative work on mobile devices

Bin Shao, Du Li, Ning Gu

Abstract: Operational transformation (OT) is a promising technique for supporting collaboration using mobile devices because it allows users to work on local data replicas even in a disconnected mode. However, as work goes mobile, a large number of operations may accumulate, defying the capacity of current OT algorithms that are mostly designed for real-time group editing. Since their assumption is that operations are propagated frequently, they generally only address how to integrate one remote operation at a time. As a consequence, most algorithms take O(|H|2) to integrate one operation and thus O(|H|3) to integrate a long sequence, where H is the operation history. This paper proposes a novel algorithm that provides optimized transformation of long sequences, improving the time complexity to O(|H|). Our experiments will show that it takes 59 minutes in a recent algorithm versus 1.5 seconds in this work to integrate two long sequences on a mobile device. The performance improvement is critical towards achieving desired responsiveness and group productivity in a class of mobile collaborative applications.