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2.1 The Message Bus

Our architecture includes a messaging component that
serves as an uniformly accessible communication channel between each client and the application server. The proposed message bus is characterized by point-to-point communication between the clients and the application server based on the request/response model. The data delivery protocol can be synchronous or asynchronous depending on the application's profile. Each client request is wrapped in a message and transmitted to the application server. According to certain meta entries of the message, the application server dispatches the incoming message to the appropriate application object regardless of the actual content of the message.

Each message is composed of a header, a set of properties, and a body. The header contains values used by both the clients and the application server to describe the structure and the content of messages in a general manner. In addition, each message provides a set of optional and extensible properties which are used by BES to specify dedicated application protocols by adding application-specific fields to a message. The body contains the data items themselves, which can be of any type that is serializable in Java.

By using messages as the exclusive communication paradigm between WWW clients and the application server, each call to remote functionalities is dispatched to the appropriate method call of the application server. Since the communication interfaces between clients and the application server do not change over time regardless of the number and type of BES which are or might be integrated in the system, no additional communication-related code has to be provided, such as compiled static interfaces like stubs and skeletons. Instead, dedicated application protocols wrapped in messages are used as generic interfaces to initiate remote requests and to transmit the corresponding response back from the application server.


next up previous
Next: RESPONDEO - A Lightweight Up: 2 Proposed Architecture Previous: 2 Proposed Architecture

Ralf-Dieter Schimkat
Thu Dec 9 14:08:00 GMT+1 1999