Research On Several Key Issues In Adaptive Synchronous Collaborative Editing Systems

Distributed Real-time collaborative editing system allows a group of users to view and edit the same text/graphic/image/multimedia document at the same time from geographically dispersed sites connected by networks. They have many applications such as collaborative writing/authoring, computer-supported cooperative learning, collaborative CAD, collaborative programming and debugging, and electronic conference, etc. They provide a convenient virtual workspace for collaboration and communication among people. In recent years, with integration of wired and wireless network technology, and widely utilization of mobile computing devices, Internet is becoming a new computing networking environment, in which people can access and acquire computation and information resources at anywhere and anytime. From the perspective of cooperative computing, Internet environment has some new features: mobility of cooperative participants and their devices, diversity of computing device and network connection. These features present as dynamic changing of participant's location and resources of computation and network in the process of collaboration. These features restrict the use of existing collaborative technologies in the new Internet environment. It is necessary to investigate new collaborative technologies that meet the needs of collaboration in Internet environment.In this paper, several key issues of Internet-based real-time collaborative editing systems are investigated, such as concurrency control and consistency maintenance in image-based collaborative editing, confliction prevention mechanisms in collaborative graphics editing, and dynamic architecture of collaborative systems. The investigation is combined with key issues in the research project of "Research on key technologies in the Internet-based collaborative pattern CAD/CAM system".A distributed Image OPeration Transformation {dIOPT) algorithm was proposed to achieve consistency maintenance of image in collaborative editing systems.An Any undo framework and related algorithms for collaborative image editing are proposed, which implements the separation of undo mode and undo mechanism. The undo mechanism supports several undo modes, and user can select different undo mode in the same editing session.An Optional and Customizable Dynamic Locking (OCDL) model and related algorithms used in objected-based collaborative system are presented. OCDL realizesseparation on locking policy and locking mechanism. User can describe a specific locking policy as needed. OCDL mechanism can adapts the locking scope and locking granularity at runtime according to user's editing activities and locking policy selected. OCDL is an optional locking mechanism, and it can be enabled when needed.An Implicit and Dynamic Locking Mechanism {IDLM) used in collaborative image editing systems is proposed. IDLM mechanism realizes locking on irregular region, and locked region can be dynamically adjusted according to the locking policy selected.A model of Messaged-based Adaptive Synchronous Collaborative Architecture {MASCA) is presented. MASCA realizes dynamic distribution of application layer and user interface layer, and supports dynamic message mapping between two layers. MASCA supports dynamic architecture transition at runtime.A collaborative message bus mechanism, which is consisted of message routers, is proposed. The mechanism provides message mapping, message transportation and shared states synchronization services for collaborative application.