Asynchronous calls, callbacks, and correlation

BPEL processes, particularly long-running processes, invoke services in an asynchronous manner. Instead of synchronous invocations, they use asynchronous invocations. Related to asynchronous invocations are callbacks. To correlate asynchronous requests and responses, we need to use correlation. In the previous chapter, we described how correlation in BPEL works. Here we will show an example in WID.

We will implement the TravelApproval process, which we introduced in Chapter 2. The client invokes the business process, specifying the name of the employee, the destination, the departure date, and the return date. The BPEL business process first checks the employee travel status, using a synchronous invocation. ...

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