[*] We would like to draw a distinction between virtual documents and the technologies used to achieve the effect of virtual documents. One can use CGI, HTML, downloadable applets, and mediating proxies to generate presentations on the fly. However, these technologies do not inherently produce results that look and feel like documents, are generative (e.g., constructed or composed from parts), and change content in response to reader input. These are the salient properties of virtual documents, however they are implemented.