Client-server Components and Metadata Objects for Distributed Geographic Information Services

The need for global access and decentralized management of geographic information is pushing the GIS community to establish an open GIS architecture and provide distributed geographic information services. From an operational perspective, the role of client/server components underlie specification of task-oriented programming, and the modularization of GIS software. Exchange of geographic information services cannot happen without development of metadata strategies for exchange of processing modules. This research proposes a flexible and dynamic Client/Server relationship in the context of Lego-like distributed GIS components, which can be moved, combined, and used in distributed network environments. Derived from generic GIS tasks, four representative client-side GIS components and two server-side GIS components illustrate the balance of functionality between client and server components. An object-oriented metadata scheme is proposed to formalize description of GIS operators as well as geospatial data sets. The metadata scheme introduces two new types of metadata for GIS components: system metadata and GIS operator metadata, which describe GIS component behaviors and specify data requirements of specified GIS operators. Distributed GIS components become reusable, modularized, self-described, and self-managing with the collaboration of system metadata and GIS operator metadata. The use of operational metadata objects is the key to interoperability and plug-and-play functions for open and distributed GIS components.