Real-time generalization of XML-encoded spatial data for the Web and mobile devices

The increased use of the Web and the Mobile Internet as a platform for geospatial applications necessitates development of improved interoperability between computing systems and underscores the need to apply standardized network technologies in processes dealing with spatial data. The generalization approach applicable in network-based spatial data services may be based on different technologies, compared with traditional cartographic generalization. Here, the use of Extensible Markup Language (XML) techniques in data transformations, with special emphasis on cartographic generalization, is presented. The research presented in the paper is focused on the Extensible Stylesheet Language Transformation (XSLT) process as a means to generalize XML-encoded spatial data in real time. The prototype system for real-time generalization developed at the Finnish Geodetic Insitute (FGI) applies Geography Markup Language (GML) as spatial data encoding and Scalable Vector Graphics (SVG) images for map visualization. The data-access interface conforms with the Open GIS Consortium's (OGC) Web Feature Service specification. The implemented generalization operators include selection, building simplification and aggregation, and were processed during the request-response dialogue in the network. The generalization process was tested on topographic datasets and results visualized on the Web and Personal Digital Assistants (PDAs). Although XML-based computing processes are generally understood to yield poor performance ratings, the work shows that intelligent XSLT generalization processes can be introduced without degrading the performance of a mobile map service.