What is Messaging?

Messaging is a means of using messages to communicate with distributed systems to perform some kind of function. Each message consists of a header and a payload. The header contains control information and the payload is the actual content of the message.

Contrary to real-time synchronous applications such as RPC (Remote Procedure Calls), messaging often operates in an asynchronous fashion, allowing messages to be transmitted reliably even when network outages occur. Think of messaging as email for applications. Emails get queued in mailboxes awaiting pickup by recipients. In messaging, messages are usually delivered via some managed queues. An example of a widely adopted messaging standard is JMS (Java Message Service).

What about XML?

Typical messaging involves a client and a server. Both the client and the server must agree on a message format. The platform-independent XML (Extensible Markup Language) has become a de facto choice of message format. Because of its interoperability and reliability, businesses have started to adopt XML messaging to build business processes across disparate application platforms in multiple locations. On the other hand, XML messaging is sometimes inappropriately used in a loose sense to represent general XML-based data communications that do not address reliability.