相对位置乐观锁机制及在协同编辑中的应用

为了满足实时协同编辑对快速响应、无约束协作的要求，提出了一种基于相对位置的乐观锁机制并发控制算法．该算法引入了编辑锁和读锁，并对加锁的起始位置和编辑操作位置用相对位置表示，当锁申请成功将写进锁表或者操作发送到各协作结点时，再把它们转换成绝对位置，加锁的粒度可根据编者的需要任意选择，编者在加锁请求获得确认前，可预先进行编辑操作．应用实例表明：该算法既保证了数据维护的一致性，又具有快速响应性．

The Optimistic Locking Algorithm Based on Relative Position and Its Application in Collaborative Editing Systems

In order to meet the requirement of quick responsibility and non-constraint in real-time collaborative editing systems, in this paper, we propose a novel responsive fine-grain optimistic locking concurrency controlling algorithm based on relative position for consistency maintenance in real-time distributed collaborative systems. In this algorithm, reading lock and editing lock are taken into account. The starting position of locking region and the position of editing operation are expressed in relative values, and they are not transformed into absolute positions until operations are sent to cooperative sites or locks are added into the Lock Table. Additionally, the locking granularity can be selected by editors optionally, and any coeditor can edit in advance before his/her requested lock is confirmed. This algorithm has been used in our collaborative editing system, and the experiments show that the concurrency controlling algorithm can well ensure the data consistency and quick responsibility.