Online Giservices @bullet from the Software Engineering Point of View

GIServices means geodata services and geoprocessing services. Most on-line GIS service systems provide centralized geodata services based on a client/server computing architecture. These systems allow users to access geodata sets from remote data repositories. With the increasing availability of geodata sources, an interesting issue is raised: can we provide users with a system allowing them to access and integrate geoprocessing functional tools over the network? This paper introduces a new technology " GIServices " and reports recent progress made toward this research direction. A distributed geoprocessing service model is designed based upon an open object architecture and a prototype system, " GeoServNet " , has been developed. It allows users to assemble, access or " rent " geoprocessing components that are distributed across a network via any standard browsers. With this model, both distributed data and GIS processing recourses can be integrated in a way that users are able to access GIServices on the Internet. An alternative development approach to GISystems would be a service-oriented approach that allows users to access, assemble, and " rent " geoprocessing components that are distributed across a network via standard Internet browsers (Tao and Yuan, 2000a, 2000b). In such a scenario, users make their data available to a GIService agent, and pick and choose the right tools to process their data sets. Users also have a full control over the entire data process. The processing can be done either remotely on a host server or locally on the user's machine. The GIService agent provides a common interface with which the geoprocessing functional components can be registered and made available. With this archi tecture, both data and geoprocessing resources distributed across the network can be accessed, assembled and even integrated by network users. Primarily, there are three reasons for developing GIServices rather than GISystems: • From the Technological Point of View The impact of the network-centric computing on GIS is unprecedented. From the technological point of view, GIS architecture has evolved: (a) From mainframe GIS to desktop GIS; (b) From desktop GIS to network-based (Internet/Intranet) client/server GIS, and (c) From client/server GIS to ubiquitous distributed GIS. With the increasing availability of abundant and cheap ubiquitous computing devices, wireless/mobile/nomadic network access, and autonomous and intelligent software proxy agents, ubiquitous geocomputing in a heterogeneous network environment defines the trends of the next generation of GISes. Therefore, it is of great value to research the new models that …