How Discoverer 3i Viewer Works

See Figure 11-1 to understand how Discoverer 3i Viewer works:

1. Discoverer 3i Viewer is invoked via a URL from a standard Web Browser, just like any other Web Site. The URL is processed by the 3i Viewer Servlet running on the Web Server.

   The servlet uses Discoverer Server Interface (Model) to communicate with the Discoverer Application Server. Discoverer Server Interface and Discoverer Application Server are both also used by Discoverer User Edition:

   Discoverer Server Interface. This is an applet but here it is running on the Web Server, rather than in the client's JVM as in Discoverer User Edition. The 3i Viewer Servlet communicates with Discoverer Application Server using Corba IIOP protocol.

   Discoverer 3i Viewer andDiscoverer User Edition use the same Discoverer Application Server.

2. Discoverer 3i Viewer Servlet interprets the HTTP request from the client browser, and makes the necessary calls to the Discoverer Application Server. The server response is represented in XML generated by the servlet and is sent to the XML/XSL processor (XSL-T Processor).

3. This combines the XML with an XSL configuration file that defines the representation of the User Interface and,

4. XSL-T Processor generates HTML to send back to the browser.

   It is the XSL file that allows the User Interface of Discoverer 3i Viewer to be customized for individual sites.

Figure 11-1 Discoverer 3i Viewer Architecture

Replicating Discoverer Application Server

The Web Server and the Discoverer 3i Viewer Servlet container can be replicated using standard web farming and virtual hosting techniques.

In a real system there would be many users using each web and application server. Discoverer allows you to determine exactly how you want the load spread across available machines.