Study On Concurrency Control Model Of Real-time Collaborative GIS

With the rapid development of computer networks and communication, the collaboration among people has adopted real-time collaborative model which is slowly developing in many areas, instead of face-to-face meeting model. It provides a real-time collaborative way of working for distributed users. In real-time collaborative model, people which are distributed in different regions don’t need to gather together to have a face-to-face meeting. This method not only save cost, but also improves the working efficiency. This new model also brings new challenges and opportunities for GIS technology. The combination of real-time collaboration and GIS is bound to become one of the future development direction. In the real-time collaborative GIS environments, collaborators work together based on a common geographic information, and achieves “what you see is what I see”. Such applications can play a big role in e-Government, the disaster emergency response system and so on.Based on the analysis of the construction of the real-time collaborative GIS based on message communication mechanism, system structure, operation mode, etc. this paper studies the core technology of real-time collaborative GIS- the concurrency control of the system. In the work environment of many collaborators to participate in, the paper discusses how to implement concurrency control to ensure that each user can quickly respond operation information with each other, again at the same time can overcome the restrictions of user action and the lack of collaborative perception in the concurrency control. The main research content and results of the paper includes the following aspects:(1)This paper analyzes the implementation of a real-time collaborative GIS based on message communication mechanism, system structure and operation mode, and the GIS operation are classified based on the GIS semantic information. The paper analyzes the GIS operations of different granularity, and extracts the semantic information of the GIS operations. Besides,the paper standardizes the GIS command message format, and formulates a set GIS command message format,GIS message storage format and operation transformation format which is suitable for flexible free and collaborative perception of concurrency control.(2)Presents concurrency control model of the GIS operation in the real-time collaborative work environment. The model covers the basic operation, spatial query operation, map editing operations and so on. Based on the semantic information of different GIS operations, we formulate a set of conflict rules, and based on this rules we formulate a set of intelligent, fast collision detection method of GIS from the various collaborative operations conflict detection on the server side.This method does not need artificial perception or manual intervention(3)If the system detects there has conflicts, then it will clear up the conflicts. This article committe to achieving freedom flexible concurrency conflict resolution strategy based on Role- Time Stamp perform priority rules. Combined with the operation conversion function to simply the information which will be sent to client.(4)Based on the concurrent control model proposed in this paper, Conflict detection and resolution methods are given to commonly used GIS operation problem of concurrency control instance verification in the real-time collaborative GIS.