The ideas for this book were conceived during the last years when I was with GIs groups at the Technical University of Darmstadt (group of Hans Jorg Schek) and at Bonn University (group of din B. Cremers). The results in the book are closely connected with two research projects that have been supported by the German Research Foundation (DFG): the collaborative re search centre (SFB 350) "Interactions between and Modelling of Continental Geosystems" which was set up at Bonn University and the joint project "Interoperable Geoinformation Sys tems (IOGIS)." First and foremost, I am very grateful...