Virtual database: Spatial analysis in a Web-based data management system for distributed ecological data

New challenges and requirements for the management of environmental data require improved data interoperability, data integration and data sharing. This paper describes the conceptual design and implementation of the Virtual Database as an integrated environmental and landscape information system which supports corresponding techniques and methods. The Virtual Database consists of a framework for advanced Webbased retrieval, analysis, and visualization of spatially related environmental data based on the integration of distributed data repositories. Existing Internet solutions for disseminating spatial data, such as geoportals or WebGIS, essentially provide functionality for searching, mapping, publishing and limited querying. The main focus of this paper is on extending these techniques by offering spatial analysis capabilities applicable to distributed data sets. The current prototype version of the Virtual Database supports methods for applying spatial filters and performing spatial overlays. The implementation is based on modular and service-oriented software design, open specifications and open source software but also considers proprietary products where appropriate. Our results confirm the strategy of enforcing openness and modularity for reasons of extendibility and maintainability.