For situations where WS-Addressing isn't appropriate or available, BPEL provides the concept of correlation sets. Essentially, correlation sets allow you to use one or more fields present in the body of all correlated messages (for example,
orderId) to act as a pseudo conversation ID (equivalent to the
<wsa:RelatesTo> properties in WS-Addressing).
A correlation set consists of one more properties; these properties are then mapped using property aliases to the corresponding fields in each of the messages that are being exchanged. The combined value of these properties at runtime should result in a unique value (at least unique across all instances of the same process), which allows the BPEL engine to ...