A reversible Web architecture for the management of geographic information

In the last year, the use of the Web for the visualisation and diffusion of geographic data is focusing the attention of developers and users: the idea to reach a wide arena of users in a friendly and simple fashion is really attractive. At a deeper analysis, however, one must admit that the user interaction and the available tools in the traditional applications for geographic data (such as image processing systems and GIS - Geographic Information Systems) are different from those offered by traditional Web sites. The former systems are richer in terms of elaboration tools and centred on the unavoidable creative activity and experience of the end user; in the latter systems the end users play a passive role (documents are selected and prepared by the site authors), interaction tools are usually limited to access and navigation, but the interaction habits are easier, and results are available without any concern about formats, active/visible layers, etc..The result of this gap is the abundance of applications which are called WebGIS or GIS online, being nevertheless systems for the delivery on the Web of images with geographic reference. In this paper we propose a Web architecture which is able to present to the users richer environments in terms of both computation facilities and interaction tools. The proposal is based on the use of open technologies for the description and display of geographic information on the Web, i.e. GML (Geographic Markup Language) and SVG (Scalable Vector Graphics). The architecture is reversible, i.e. not only information but also their elaboration/manipulation tools can be suitably exchanged/transformed through the components of the Internet, whereas in the traditional Web architecture information are distributed from the server(s) to the browser(s) in a one-way fashion. The idea is illustrated here in a case study represented by a CBIR (Content-Based Information Retrieval) system of remore sensing images. This system, called SIRS (Signature Information Retrieval System) [1,2] is based on a model allowing to index and retrieve images by means of their spectral properties