Traditionally, SVG maps could be edited and rendered using a variety of approaches.Once published, rendering is normally a client-side application that does not re-connect with the server.Because of this, information has to be released to all users, although in many cases not all clients are expected to access some of the certified and/or classified information.
W3C's Web service enables decomposing the software into functional components that can be accessed and integrated through the standard Web Services Description Language (WSDL) interface.In this way, GIS functionality for data processing and spatial analysis can be componentized and further integrated to support Web GIS applications using SVG as the map format.This helps open up SVG to allow certain processes on data that needs to be secure (e.g.certain attribute data) to remain secure, while permitting freer passage of data that does not need to be secure.
WSDL Web service provides a way to connect the client-side SVG viewer with the server functions to process data, perform query functions on both spatial and non-spatial features and redraw the SVG map.By separating spatial and non-spatial features, SVG can only be a graphic format with screen canvas x, y coordinates.The secured non-spatial attribute data can be processed and accessed through the WSDL Web service.Such a query can be dynamic; the SVG map will be updated and redrawn by the service command on request.Using this approach, what the user can see in the SVG source code is only the x, y screen canvas coordinates as well as the graphic styles, without any attribute values.
Figure 1 shows such an example.Private parcel information is not open to the public.When SVG is used in this application, the parcel dataset is separated from the spatial features.While the SVG map is generated and updated in an ASP.NET Web form, the non-spatial parcel data is served through a Java Web service created by WebLogic 7.0 with MySQL database, which also supports the non-spatial attribute query.A qualified client can access the secured parcel data and perform query functions on it.The SVG map viewer only contains the spatial feature coordinates as well as the mapping styles.
WSDL Web service will change the way traditional GIS functions are performed on the Web.SVG use in GIS is promising, as an SVG viewer can be enhanced and supported with GIS functions.According to an editorial from 2002, the future of Web service application in GIS "holds great promise for dedicated spatial service developers and integrators whose imagination will be the primary limit to the applications that can be built" (Ball, 2002).