Real-time Collaborative Editing System Synchronization And Reliability Study

Real-time graphics collaborative editing systems are representative groupware systems in the area of CSCW. They allow physically dispersed multiple users to view and edit a shared document at the same time over communication network. To support free and natural interaction, the all-replicated architecture should be used. The key problems in studying and designing the real-time cooperative editing system are node synchronization and reliability of the system, which are also the main contents discussed in this paper.This paper studies the cause and representation of intention conflict, causality conflict and late-joining conflict based on a consistency model deeply. The concurency control algorithm based on object replication is discussed, which can resolve the conflicts caused by geometry attributes and maintain the operation intention. A delay-operational recall algorithm based on operation delay list is stated out, which can resolve the causality conflict efficaciously. In addition, an improved multiple servers algorithm is brought forward, which can initialize the state of the late-coming participant and resolve the reliability problem of the late client to join an ongoing session.At the same time, the dependability maintenance of systems is analyzed. The preserved userinfo is same between server and client nodes in an all-replicated architecture. So this paper presents a distributed-backup reliable model based on fault-tolerant to ensure that the system can run normally. The system chooses a collaborative node to substitute main server according to control measures when the main server cannot work.In this paper, CoDraftPaint system, which is a prototype system of the object-based real-time cooperative graphics editing system, is introduced. As a prototype system of real-time collaborative editing, the CoDraftPaint system implements all algorithms proposed in this paper. All researches in this paper are verified in the prototype system.