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304 webMathematica User GuideDynamic HTMLWhen the web was first developed, it supported only the distribution of static pages. The technol -ogy was extended to allow interactive access for dynamic content generation.Fundamentally, the web is driven by its main protocol, HTTP (Hyper Text Transfer Protocol),which imposes certain constraints. Under HTTP, a client sends a request to a server that replieswith a response. A crucial feature of HTTP is that it is stateless; that is, after processing arequest, no record of that request is kept. Of course, state information can be maintained viasome other mechanism; for example, the servlet API has methods for keeping state that can beused with MSPSessionVariable.This reference section reviews server and client technologies for dynamic web content. Becausethis field changes very rapidly, the survey is not intended to be exhaustive.Server TechnologyThere are several server-side technologies for dynamic content. These include CGI scripting,Active Server Pages, server plug-ins, Perl scripting, and Java servlets and JavaServer Pages.CGI ScriptingCGI scripts provided the original server technology for dynamic content. Under CGI, an executable,such as a shell script or compiled binary, is launched on every request.This mechanism is limited in a number of key ways. It is relatively expensive since it requireslaunching a new CGI process for every request, which can cause scalability problems. Onesolution is to make the actual CGI script a lightweight process that communicates with its ownserver; many web solutions actually do this. Of course this requires nontrivial development andcan result in something that is more complicated to use than other dynamic solutions.