2.2.2 Application Management Functionalities   RESPONDEO offers several management functionalities to each application object regardless of the actual type of BES. For each BES, it manages a single instance or pool of instances of the corresponding application object. When an incoming request has been processed, the active application object is enqueued into the provided pool for future client requests. If there is no application object available for processing an incoming request, the request is blocked until the application object pool can offer the object. The size of the pool can be configured and changed at run-time in order to adapt the scheduled number of application objects to the currently active number of WWW users and the processor's load. By controlling the entire communication process between client and backend servers through an additional level of indirection, RESPONDEO shields the backend servers from the total load. By providing only stateless objects, all resources (number of application objects for each BES) are configurable, controllable and predictable regardless of the number of WWW clients trying to access the BES. RESPONDEO strictly separates application- and communication-related logic by wrapping application objects and client requests in standardized messages. Thus, the communication level of the proposed architecture has to deal with messages only regardless of their application specific content, i.e. the application logic. Our architecture provides various kinds of communication channels which can be switched dynamically at run-time, e.g. the compression and the security channel. In the former one, all messages are compressed in order to reduce bandwidth. The latter one provides a secure data transfer on the message bus between clients and RESPONDEO. As far as RESPONDEO is concerned, communication channels can be aggregated and plugged together in order to build customized channels which communicate down a single network connection.