This image describes the Oracle9iAS Discoverer architecture. There are four pathways through which you can access the underlying database:

• Administration applications access the database directly.
• Discoverer Desktop accesses the database directly from the client machine.
• Discoverer Plus uses a Java applet to access Discoverer Services, which connects to the database.
• Discoverer Viewer runs in a browser, and uses a servlet to access Discoverer Services, which connects to the database.