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Summary - In this article, the first of three, Dirk Reinshagen discusses XML messaging, specifically the basic premise of XML messaging, what it is, and why it is useful. Further, he presents a simple XML message broker for custom XML messages. In the course of developing this broker, he introduces general broker development strategies. In Part 2 and Part 3, Dirk will discuss the two emerging standards for XML messaging: SOAP and ebXML. (1,500 words)
XML messaging represents a rapidly growing, dynamic area of IT, a situation that makes it exciting and tiresome at the same time. As B2B exchanges and other forms of inter-business electronic communication grow, XML messaging will be more widely deployed than ever.
In this article, we'll first explore XML messaging and why it is useful. Then we'll delve into specific XML messaging features, including message routing, transformation, and brokering. Finally, we'll finish up with a simple example of an XML broker. After you read and understand the concepts, you should clearly understand which scenarios lend themselves to implementing an XML messaging solution.
What is XML messaging?
To start our exploration, we need to understand the basic premise of XML messaging and what the term messaging implies. For purposes of this article, I define message as follows:
A collection of data fields sent or received together between software applications. A message contains a header (which stores control information about the message) and a payload (the actual content of message).
Messaging uses messages to communicate with different systems to perform some kind of function. We refer to the communication as being message-oriented because we would send and receive messages to perform the operation, in contrast to an RPC (Remote Procedure Call)- oriented communication. A simple analogy may help: think of messaging as email for applications. Indeed, messaging possesses many of the attributes of individuals sending email messages to one another.
In the past, when you were using or working on a message-oriented system, it meant that you were using some kind of MOM (message- oriented middleware) product like Tibco's Rendezvous, IBM's MQSeries, or a JMS provider to send messages in an asynchronous (one-way) fashion. Messaging today doesn't necessarily mean that you are using a MOM product, and it doesn't necessarily mean...