In a messaging environment, messages will be constantly flowing in and out of the system. Often, the messages will be part of a business process. In order to track this process, a shared identified can be attached to messages to link them together to a single process.

For instance, when handling a purchase order, there may be three messages associated with each order:

1. Original purchase order

2. Purchase Order Confirmation

3. Shipping Confirmation

Commonly, a unique purchase order number is assigned to the order, and can then be used to track the order throughout its lifetime. Similarly, each associated message can carry this identifier so we can tie the process together for monitoring purposes.

-- MikeRettig

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Very good. I HaveThisPattern! I've seen the same thing used in messaging systems for options and stock trading except the unique business process identifier was an "order number" used to link together orders, order cancellations and order changes.

-- KyleBrown