BizTalk is a message-oriented middleware, which means that all the communication between BizTalk and any external system happens by exchanging messages. In BizTalk, all messages are internally converted to XMLthat adheres to the specified XML Schema Definition (XSD).
The architecture of BizTalk server 2004 can be broadly divided into the Messaging System and Business Processes (Orchestrations). While Messaging involves receiving, storing, and forwarding of messages and interacting with various external systems, Orchestration is where the business logic is executed.
The following figure describes the architecture graphically:
A message ...