Research On Concurrency Control Mechanism In Collaboraive Design System

With the development of computer technology, network tecImology anddistribution tecImology, the trend of compuler application is towardscollaborative work between multiple users. It is inevitable that there will ariseinconsistency when a number of designers work concurrently on sharinginfOrmation. Managing the consistency of distributed data is a critical issue formany collaborative systems. In a shared multi-user environment, in order toavoid inconsistency, increase efficiency, and ensure successful cooperation, it isimPortan to coordinate the 8Ctions of the design members.In this thesis, concurrency control mechanism is studied in depth Which isused when multiple users access sharing data simultaneously. Access controlmechanism is also discussed. The main contents are listed as following:l. Collaborative design system framework and collaborative design modelBased on the analyses of collaborative suPporting environment, theproperties of collaborative design, collaborative work pattem and collaborativemode, a system framework of collaborative design is presented. And acollaborative model with hierarchical structllre is constructed.2. Concurrency control in collaborative designCombined with the property of engineering design and developed from theresearch of traditional concurrency control policies, a queuing str8tegy forconcurrency control system is presented, Which satisfies the real-timerequirements. This concurrency control system is aPplied to the collaborativemodel introduced in the thesis. The priority levels of thc transactions arcconsidered as the basis for queuing. To keep the data consistefit and iniegratedfor a real-time transaction, exclusive lock is adopted. When there arises accessconnicts, the transaction with a higher priority level can execute earlier, Whilethe lower one mny be deprived of operating right. The version control mechanismneeds to be used to save What the lower one has done.3. Access conirol in collaborative designAn access control model is presented in this thesis which is also based on thefthierarchical structure model. It supports hierarchical right mechanism, supports negative rights, supports inherited rights and supports multiple users.4. Concurrency control system implementationCorresponding to the collaborative design model, a concurrency control system is designed and implemented partly to apply the concurrency control mechanism discussed above to support collaborative design.This thesis serves the national 863 planned project ?"2001 AA41 1320 regional modern integrated manufacture system development and application at the core of Chengdu, Deyang and Mianyang" and the key project of Sichuan Province science and technology ?"99A013 the engineering framework intelligent CAD technology oriented the procedure of design ".