REAL-TIME GENERALIZATION OF GEODATA IN THE WEB
Lassi Lehto, Tiina Kilpeläinen · 2000
The growing demand for dissemination of spatial data in the Web gives at the same time new challenges also for the problem of generalization. The Extensible Markup Language (XML) technology is widely regarded as a basis for general data processing in the Web. The Geographic Information (GI) community has also started adopting XML techniques for GI processing on the Web platform. Once XML-based GI resources and services start proliferating in the Web, means are needed to transform the original data into an appropriate form for the given end user task and device. In this paper, the Extensible Stylesheet Language Transformation (XSLT) is introduced as a tool to perform real -time generalization of XML-encoded spatial data. Certain generalization effects can be achieved by filtering the source data according to pre-defined rules, by selecting a proper geometry from a set of alternative geometries, and by setting the style properties appropriately. The XSLT extension mechanism enables generalization methods based on sophisticated coordinate manipulations, e.g. line smoothing, to be performed. The paper concludes by presenting a three -tier pilot system, developed at the Finnish Geodetic Institute (FGI), consisting of a Smallworld database server, a Java Servlet middle layer and a Web browser-based visualization layer.