ABSTRACT
In the preceding chapters, we have looked in detail at the mechanics of placing geographic information online. However, the real power of the Internet lies in sharing and distributing information. Geographic information is intrinsically distributed. Whether it be mines in Canada, roads in Britain, or lakes in USA, most geographic applications concern particular themes within particular regions. To compile an overview of (say) the worldwide distribution of a single theme, or else to overlay a number of themes for a given region or country, you usually have to collate information from a number of different sources.
