Researches on Software Architecture in Emergency Response Network Spatial Information System

Software Architecture design is to be a key step in the process of software development. For large and complex emergency network geographical information system in practice, it is ridiculous to achieve the goal of emergency management based on unsuitable software architecture. At present, the network geographical information system software architecture can be divided into four layers: display layer (client), application server, spatial object server, database server. Most GIS products of major R & D manufacturers and research institutions comply with the rule. These network geographical information systems, according to their software architecture, are centralized software; the main features are data centralized and functionality centralized. The benefits of centralized software are easy development and deployment, spatial data and the function modules can be pooled in a single server, the higher the centralization, the simpler the deployment. It does not need to consider the direct data transfer in service layers and possible abnormal network transmission. Disadvantages of centralized deployment are, for the calculating job located on a single server, compute-intensive and instable Service. Because of the solo deployment, these systems cannot be restored or backup in a timely manner, from any harm to the system own safety and emergency communications, the system is fragile. In contrast to centralized network GIS, recently proposed GRID GIS, has distributing function modules and data source. Grid GIS is in fact a Grid Technology reflection in the form of Spatial Information system. GRID GIS store all the location related information in digital form and share them together as a wealth of resources via network. For its inner characteristic of distribution in functionality and data source, GRID GIS greatly improve reliability in the emergency management. While for the same reason GRID GIS is more complex in development and deployment, as well as high maintenance costs and lower system efficiency. Through analysis and synthesis of demands of both Network GIS and emergency information system in software architecture, this paper studies the suitable software architecture for ERNSIS (emergency response network spatial information system). By comparing the software architectures in centralized network GIS 、Grid GIS and the P2P software, a hybrid software architecture was proposed, which including three points: After deeply analysis of the network node in ERNSIS – namely execution node, this paper make definition of its functionality and covered data,put forward its spatial data preservation strategy and safety evaluation algorithm. For the first time this paper proposed the self wake-up message server queue, it will function with the message server for communication among the execution nodes, building a routing table with automatic updates, has automatic wake-up characteristic in servers queue, with less network resources occupancy, and higher reliability . Raise a push-pull mechanism to send a mixed message. It combines the two commonly used messaging mechanism, using push mode to ensure that the timeliness of communication and using pull mode in order to check communication validity. In conclusion, results of the three research parts are adapted to ERNSIS requirements of software architecture, that is, under the guarantee of the system response time, improved the system reliability and stability.