Introduction - Business and Scientific Workflows - page 17

and so on

Figure 1.8 An online book selling process in BPEL.

Think of an online book selling application that is implemented in
BPEL, as illustrated in Figure 1.8. A customer (through either a Web
interface or software application) sends a new order message to the
< receive > activity. The process initiates internal variables with the
order received in the first < assign > activity, and then invokes the order
fulfillment Web service (through the < invoke > activity) to determine
the availability of the topic, payment status, and so on. When the order
fulfillment service returns a result, an order confirmation message is
prepared in the second < assign > and the process responds to the
customer regarding the status of the order, that is, successful or not.

Web Services Choreography Description Language (WS-
CDL). Different fromBPEL,WS-CDL [26] is not targeted at describing
one executableworkflow. Froma global viewpoint, it defines the peer-to-
peer collaboration of services by specifying the ordered message
exchanges between them. That is to say, it abstractly describes the global
observable behavior ofmultiple parties in a collaboration.WhileBPEL is
called a service orchestration language,WS-CDL is usually referred to as
a service choreography language.