The IBM® Content Classification three-tier architecture comprises data, application, and presentation layers.
- Data layer
- This layer is responsible for storing configuration information. The system stores its data in a dedicated data server, which is installed with the Content Classification components.
Application layer 
- This layer is the core of the system and provides various services
such as language analysis, instance pooling of knowledge bases and
decision plans, and management of the distribution of tasks across
computers. It is accessed through client APIs that are provided for
writing client code that communicates with the system.The application layer comprises several server-side components:
- Listener
- The listener serves as the entry point to the system. Client requests
are sent to the listener, which then dispatches them to the appropriate
server component for processing. Requests related to a specific knowledge
base or decision plan can be routed to the corresponding knowledge
base or decision plan instance, and administration requests are routed
to the administration component. By default, the listener balances
the load of read-only requests between the available read-only instances.
- Read/write instance
- A read/write instance handles requests to the knowledge
base or decision plan, such as matching, feedback, language identification,
and modifications made to the knowledge base or decision plan. There
is one read/write instance for each knowledge base and one read/write
instance for each decision plan. You can configure a read/write instance
to forward read-only requests and balance the load between available
read-only instances.
- Read-only instance
- Read-only instances, which are optional components,
handle read-only requests that are forwarded by the listener or a
read/write instance, depending on your configuration. Common read-only
requests include matching, language identification, and viewing the
structure of a knowledge base or decision plan. You can configure
any number of read-only instances for a given knowledge base or decision
plan and configure them to run on any number of computers.
- Administration
- This component handles all global administration requests, including requests that originate from the Management Console. The administration process is configured to run on a specific server when Content Classification is installed. Communication between the various server-side components is accomplished through SOAP.
- Presentation layer
- This layer, which communicates with the application layer through
a client API, performs data layout and formatting actions. Content Classification includes C, COM, and Java™ client APIs. In addition, applications
can interact with the system by using the SOAP protocol. For example, Content Classification might be included as
a web reference in any .NET application. In most cases, you develop
your own presentation layer that fits in with the rest of your application
suite.
Several configuration options are supported to accommodate varying client needs. Regardless of the type of system configuration that you choose, you can administer all system components from a single point because all configuration data is stored in a common data server.