Research And Implementation On Concurrency Control Of Collaborative CAD System

Distributed collaborative CAD system is a typical branch of CSCW. It supports a group of designers from different sites to accomplish the same design by cooperating and communicating with each other, which meets modern pattern of information technology and becomes a promising research area. Managing the consistency of distributed data is a critical issue for most collaborative systems. Therefore, it is important to research concurrency control of collaborative CAD system.Aiming to develop a CAD system of real-time collaboration, unforced communication and easy to use, this dissertation focuses on the deep countermeasures of concurrency control mechanisms and access control mechanisms; the method implements the collaborative CAD system using dynamic locking of multi-version. The main works are listed as following:1. Based on the analyses of collaborative design's properties and collaborative work pattern, a systemic framework mode of leaning to replicated architecture is introduced.2. A new mechanism called DLOMV of dynamic locking of multi-version is proposed based on the traditional two-phase locking of multi-version. DLOMV has integrated the merit of high concurrency in multi-version mechanism and flexibility in dynamic locking policy, which enhances the coordinative system responsiveness and interaction. For better maintaining consistency, the undo/redo operations based on the user role are also proposed.3. Based on the analyses of access control modes ,an advanced mode SRBAC is introduced to improve the traditional role-based access control. The roles' permissions become more flexible by defining workgroups' permission, SRBAC supports multiple roles dynamically assigned , inherited roles,negative permissions and inherited permissions, which is especially adapted to large collaborative system, and intergrates authentication, data encrypted to protect information security. 4. Improving the collaborative Doctor CAD system. The dynamic locking of multi-version policy and the SRBAC mode have been checked and implemented in Doctor CAD. After detailed introducing the framework and functional modes of the doctor CAD, the flow chart of arithmetic and interfaces are particular described.The experiment has proved that the Doctor CAD System has the open style structure and has effectively verified the related technology proposed in this thesis. Doctor CAD has high responsiveness, concurrency and dynamic compatibility, and can carry on conflict processing effectively.