XML makes it possible to add semantic information to a HTML document so that trading partners can understand the meaning of various fields in the document. Figure 1 shows a common model of how the web operates to provide interactive services such as shopping, database access, etc. Client connects to server and downloads a form. Client fills in information on the form and submits it. CGI program on the server processes the form.
Server sends reply to client.
While it works very well for a variety of applications, there are other instances where it is not so effective. In particular, some of the problems are as follows. First, it is not always possible to establish a connection between the client and server either because the underlying network is unavailable or the server is overloaded. Secondly, this is not a very efficient way of communications when a large amount of information has to be exchanged. Thus, there is a need for a framework that exploits the advantages of the web, and yet provides better support for asynchronous, flow-type commercial applications.