Correlation and message properties

Business processes use a stateful model. When a client starts a business process, a new instance is created. This instance lives for the duration of the business process. Messages sent to the business process (using operations on port types and ports) need to be delivered to the correct instance of the business process. We would expect this to be provided by the runtime environment, such as a BPEL server. This is the case if an appropriate transport mechanism can be used, such as WS-Addressing. However, in some cases where several partners are involved (for example if the BPEL process calls service A, which calls service B, and service B makes a direct callback to the BPEL process), or a lightweight transport mechanism is used that does not provide enough information to explicitly identify instances (such as JMS), manual correlation is required. In such cases, we will have to use specific business data, such as flight numbers, social security numbers, chassis...