Message Correlation

Correlation is an activity that uses a message identifier for matching messages.

A message identifier is a piece of information that is used to establish a relationship between one or more messages.

Various requirements and higher-level features identified in this architecture lead to the need for message correlation. For example, asynchronous interactions often require higher-level correlation between otherwise distinct messages. One implementation of this concept makes use of identifiers for correlation itself, allowing a response to be correlated with the original request. The message identifier is an identifier that allows the response to be correlated with the originating request. The sender may also add an identifier for a service, not necessarily the originating sender, who will be the recipient of the message. The message identifier can be passed in one of three ways:

1. message identifier in message
2. message identifier in interface
3. message identifier identified by a URI and retrieved from a 3^rd party

Who does Correlation?

• Protocol – Correlation is done by the underlying protocol
• Infrastructure – Correlation is done by the infrastructure, the message identifier not available to application/user and
• Application – Correlation is done by the application. Application uses the message identifier directly and it must be passed thru and available to him. The need for the application to do that depends on how much infrastructure he can depend upon.

Examples of types of correlation:

• Reliable Messaging – storing and resending a message
• Asynchronous Request Response – Need a correlator to know that a message is the response to a request.
• Session –
• Application – application may need to correlate messages over a session
• User – SessionID might be used as a message identifier for sessions or conversations
• Pub Sub – Message is a result of a particular subscription