Page 1 of 3 Next Associate Professor Faculty of Geoinformation Science and Engineering Universiti Teknologi Malaysia Email: alias@fksg.utm.my Current GIS software excellently manages our geo spatial data. However, the world of geo spatial information requires more advanced tools to manage more complex real world. 3D situations as we have in city centres, subsurface objects, and the like are really best manage by 3D geo spatial software. Traditionally, any GIS are based on the principles of data input, management, analysis and representation. Within a web-enabled environment, these principles are represented by or implemented within certain components. In order to achieve communication between the different components (refer Table 1) in a web environment, a web server is common. Since the geo-data is a very specific type of data, different standards, e.g. the OpenGIS Consortium (OGC) specifications are already developed and their utilisation has to be considered (see below). A system composed of these components is called Web-GIS. It should cover a complete GIS workflow within a Web environment. Figure 1 shows the general system architecture which is mostly "Client-Server".  Figure 1 shows the minimum system architecture of Web-GIS. The Client is an application, which can communicate with the Server through a standard web protocol, for example HTTP. This application can either be in form of a web browser or standalone utility. In order to view and interact with GIS data, the browser needs to be extended by using an adequate Plug-In, Java Applet or both. Instead a standalone application can be used. This can be for example any GIS, which is supporting the appropriate protocol to access other computers in computer networks. The web server is responsible for processing the request from the client and delivering the corresponding response. In Web- GIS architecture, the web server is also communicating with the server-side GIS component. This is adding spatial analysis functionality to the system. Moreover, server-side components are responsible for the connection to the spatial database, such as translating queries into SQL and creating appropriate representations to be forwarded to the server. In reality, GIS components are software libraries, which are offering classes to do spatial analysis on data. Besides the components, a very critical aspect is the functionality offered by the client- or server-side within Web-GIS. Figure 2 shows possible distributions of functionality for a client-server system based on the concept of the visualization pipeline (OGC, 2003b).  Figure 2 shows that a client is considered "thick" or "fat", if the main GIS functionality and the data rendering are client-side hosted. Consequently the server in this specific system would be called "thin". The server is called "thick" if GIS functionality and pre-rendering is hosted server-side. Within this system, the client would be called "thin". Altmaier and Kolbe (2003) exclude rendering for interactive 3D worlds on the server since realtime navigation in static images would not be possible anymore. However, it is still an interesting question how to find the balance between server and client. Because of the system complexity, required functionality, type of application, data sets, even available funds for implementing one or another solution and user experience, no ordinary rules can be specified. The question has to be answered for each system individually. Regarding the general system architecture, 2D/3D Web-GIS don't have many differences. The setup shown in Figure 1 can be used for both.
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