摘要
介绍了中间件技术原理，说明了SDE在系统中的工作原理，并以南海市国主管理信息系统的设计与实现为例，介绍了应用中间件技术的GIS的研究与实践。
The rapid advance of middleware technology is one of the most important characteris-tics in softwar development in recent year. This paper intreduces the application of middleware technology, the software and design of the Nanhai land administration information system (NHLAIS).CORBA and DCOM provide complete and effective mechanism for the application, combina-tion and management of software from different platforms. These series of technological break through bring out the combinization of software application and the componentization of software preduction. By combing the different software from different places effectively, the cominization roolves the application problem. The software system is decomposed into several independent components by the componentization technology of software preduction. Through standard system,,enviroriment such as ActiveX and OpenDoc, these GIS cornponents can realize the system combi-nation effectively by connecting with other non-GIS components. The middleware refers to the fortware Shielding the difference between the operation system and netware protocol, providing the cornmunication service among the system of different architectures. The Client/Server mode of three tiers based on middlewarc divide the application logic into three parts. Indication logic (Client tier)-the first tier, realizes the friendly interaction between the user and system,transers the coral servicr the operation logic, displays the operation result. Operation Logic (Server component ) - the middle tier, realizes the coral operation logic, manages and receives service request from the Clients, transfers data operation to mrce manaper, returns the operation result to the applicants-Client or other Server. The management of data of application system is executed in the data manager-the third tier. In general the middleware has the following categories: remote procedure call(RPC), message-oriented middleware(MOM), object request brokers(ORB), database access(DA), and distributes transaction processing(DTP).NHLAIS is a wild area network (WAN) system. The center of the network is located in the Nanhai City Land Bureau. The 20 town suhbureaus serve as the nede of the network. Inside the City hand Bureaus a 100MB local area network (LAN ) based on TCP/IP adapting Windows NT fferver and Windows 98. A proxy fferver communicates with the ISP through optical fibre. The application program in the workstations of the town sub-bureaus communicates with the ISP through the dialing mede. The non-spatial data is managed by SQL Server 6. 5 from Microsoft.The SDE for SQL Server from ERSI manages the majority of the spatial data. With SDE the speed of loading map is enhanced. The cleaveless space database is established. The burden of the network is lowered. In NHLAIS, the Active Report of microsoft is adapted for the report output.MO from ESRI is adapted for the communication with different categories of map.
出处
《武汉测绘科技大学学报》
CSCD
1999年第4期331-335,共5页
Geomatics and Information Science of Wuhan University
基金
教育部博士点基金!97049803
