The database includes all 50 US states and the District of Columbia. It's underlying technology is applicable to a range of data types and illustrates the potential for interactive visualization of interdisciplinary spatial data. Introduction Over the past three years a variety of mapping applications have been developed for use over the Internet. It uses Java client-server technology to retrieve demographic data over the Internet and create maps on the user's desktop. The client can be loaded through a Web browser on any Pentium-class PC or UNIX workstation.
Users select a region of interest from a map and a set of variables from a listbox tool.
Both input and output maps have interactive features. The demographic variables were derived from the US Bureau of the Census STF3A 1990 files. This national database is centrally stored and maintained on the server. This prototype was followed by a national 1990 census data mapper developed by Meij and Xiaoshi Xing and released as DDViewer 1.0 in 1996. The underlying national-level SAS database used in all versions of DDViewer to date originated in this version.